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Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering
Journal Prestige (SJR): 0.422
Citation Impact (citeScore): 1
Number of Followers: 41  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0954-4100 - ISSN (Online) 2041-3025
Published by Sage Publications Homepage  [1175 journals]
  • Design of a non-cooperative target capture mechanism for capturing
           satellite launch adapter ring

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      Authors: Yongjun Sun, Qian Wang, Rihua Jiao, Rongqiang Liu, Minghe Jin
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Space debris is growing dramatically, which poses a serious threat to space exploration activities. Especially the large non-cooperative target, such as malfunctioning satellites. This paper proposes a capture mechanism for the launch adapter ring that is usually available on satellites as the capture object, which used for in-orbit capture of malfunctioning satellites. Firstly, introduce the design conditions, the overall design plan, carry out the mechanical mechanism design, sensor system configuration, electrical system design, and explain the capture process. Secondly, analyze the capture tolerance. Thirdly, by establishing the kinematics model of the captured finger, use D-H parameter method for kinematic analysis, and analyze the dynamic in the capturing process. In addition, the control strategy is proposed, and the clamping force model, friction identification model, and servo control strategy are established. Then, the prototype is manufactured, and the clamping force, stiffness, capture loads, and capture tolerance are tested. Finally, the air-floating platform is used to verify the capture test of the launch adapter ring in a microgravity environment. The experimental results show that the developed capture mechanism meets the design conditions and has the ability to capture launch adapter ring of satellites in orbit.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-29T02:34:22Z
      DOI: 10.1177/09544100221116759
       
  • Towards a formalized model-based process for the design of high-speed
           aircraft and related subsystems

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      Authors: Davide Ferretto
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Increasing complexity associated to advanced aircraft concepts for high-speed flight is pushing the limit of engineering practices concerning design phases of products lifecycle. Specific methodologies aimed at managing requirements over the entire vehicle architecture definition shall then be properly formalized and supported by means of standardized processes and languages in order to be effective. The approaches suggested by the Systems Engineering practices, especially when considering the model-based environments as main tools for systems design, can be exploited to face these challenges, if properly tailored to suit the specific engineering field considered. This paper aims at proposing a model-based process for the design of high-speed aircraft exploiting a formalized methodology and the typical tools of Systems Engineering. A conceptual design exercise, based on the STRATOFLY MR3 hypersonic cruiser case study, is performed from high-level stakeholder objectives to vehicle performance estimations, passing through functional and interface analyses. Additionally, some insights concerning on-board subsystems sizing activities are provided in terms of integration within the high-level design process. The whole work highlights the capability of performing a seamless requirements management and development within the design procedure, particularly focussing on the relationships among the different stages of the workflow.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-29T01:55:01Z
      DOI: 10.1177/09544100221141942
       
  • Supersonic flow investigation of a drag reducing conical spike on a
           hemispherically blunted nose body

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      Authors: MD Gulam Sarwar, Priyank Kumar, Sudip Das
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Experiments and computations were made at a Mach number of 2.0 on a hemispherical blunt nose body with a conical spike of L/D ratio = 1.0. Attempts were made to alter the axisymmetric cavity formation between the spike tip head and the blunt base body. Qualitative measurements and quantitative details indicate the changes which support the drag reduction beyond the conventional sharp spike. Additional drops in drag values were observed by the techniques used in the present investigation. A linear trend of drag reduction is obtained with conical spikes which lead to the drag of a pure conical body.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-26T10:58:31Z
      DOI: 10.1177/09544100221140942
       
  • A prescribed time attitude control method based on thrust vector control
           (TVC) nozzle for solid propulsion satellite

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      Authors: Zhongjie Meng, Junjie Lu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      With the development of on-orbit missions, solid propulsion technology is applied to the rapid orbital maneuver of satellites. During solid propulsion maneuver, the position change of the mass center caused by the fuel consumption and the installation error of thruster have brought serious attitude disturbances. For this problem, a novel prescribed time attitude control method is proposed in this paper. Firstly, a dynamics model of the solid propulsion micro-satellite is established, while the thrust direction is adjusted by the thrust vector control (TVC) nozzle. Then, a constraint boundary function is constructed to characterize the strict fixation of the thruster operating time and an adaptive fuzzy observer is developed to quickly estimate the lumped model uncertainties. Using the backstepping method, a novel prescribed time attitude control strategy regardless of initial conditions is designed. Simulation results show that the designed controller can achieve the prescribed time convergence of satellite attitude during solid propulsion orbital maneuver, effectively.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-25T07:29:50Z
      DOI: 10.1177/09544100221140446
       
  • A unified representation and retrieval of 3D grain configuration based on
           signed distance field

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      Authors: SUN Jingbo, WU Zeping, YANG Jiawei, WANG Wenjie, PENG Bo, WANG Donghui, ZHANG Weihua, ZHAO Hailong
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this article, the design and development of a 3D grain configuration representation method with small data and high accuracy are presented, by which a unified grain database is established. There are two vital components in our proposed method: the traditional signed distance field (SDF) method is used for the unified representation of the 3D grain configuration; the proper generalized decomposition is employed to decompose the original SDF function to compress the data. With the proposed method, the reconstruction of 3D grain configuration is realized with small data and high accuracy, based on which the similarity measurement of different grains is proposed and the reuse of the 3D grain configurations is realized. The efficacy and accuracy of the proposed method are validated by reconstructing 3D grain configurations and the burnback curves of two different grain models. The similarities of the eight grains are calculated, which are accurately consistent with the burning surface area calculations results. The experiment results demonstrate that the proposed methods are feasible and efficient, and are significant for design case data and knowledge reuse.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-24T02:10:15Z
      DOI: 10.1177/09544100221138994
       
  • Towards improved understanding of aerodynamic impact of helicopter on ship
           deck flow environment using SDI model

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      Authors: S Shukla, SN Singh, SS Sinha, R Vijayakumar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An early estimation of the ship–helicopter dynamic interface flow environment is one of the most challenging and precarious tasks in any naval organization across the globe. The First-Of-Class Flying Trials (FOCFT) is one of the most common methods to evaluate the complexities associated with the ship–helicopter dynamic interface. These trials are very expensive and highly demanding, with added limitation that these can be conducted only after post-construction of the ship and restricting the scope of any further design modifications. This study presents an investigation to gain understanding of the aerodynamic impact of helicopter on shipboard flight deck flow physics under a ship–helicopter dynamic interface flow environment. The prime goal of this work is to investigate the influence of helicopter downwash aerodynamics over the ship flight deck using the simplified dynamic interface (SDI) model. A parametric analysis has been conducted for three identified rotor configurations at different crossflow conditions. The paper reports the influence of rotor ground effect over the flight deck region in terms of the downwash airflow characteristics, variation of rotor plane velocity gradients and the airwake existing over the flight deck region. Finally, an attempt has been made to grade the effect of ground on a ship–helicopter dynamic interface for safeguarding the helicopter operations.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-22T09:07:21Z
      DOI: 10.1177/09544100221140624
       
  • Investigations on vortex evolution and wake dynamics of bio-inspired
           pitching hydrofoils

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      Authors: Yefang Wang, Lei Shi, Annie-Claude Bayeul-Lainé, Olivier Coutier-Delgosha
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Recently, lots of oscillating targets inspired from motions of some insects and birds have been applied extensively to many engineering applications. The aim of this work is to reveal the performance and detailed flow structures over the pitching corrugated hydrofoils under various working conditions, using the SST [math] transition model. First of all, the lift coefficients of a smooth oscillating airfoil at different reduced frequency and pitching angles show a good agreement with the experiments, characterized by the accurate prediction of the light and deep stall. For the pitching corrugated hydrofoils, it shows that the mean lift coefficient increases with the pitching magnitude, but it has an obvious drop at high reduced frequency for the case with large pitching amplitude, which is mainly induced by the pressure modification on the surface with smooth curvature, depending on the oscillation significantly. In addition, the mean drag coefficient also indicates that the drag turns into the thrust at high reduced frequency when the pitching amplitude exceeds to the value of 10°. Increasing the reduced frequency delays the flow structure and leads to the deflection of the wake vortical flow. The Reynolds number also has an impact on the hydrofoil performance and wake morphology. Furthermore, regarding the shape effect, it seems that hydrofoil A (consisting of two protrusions and hollows and the aft part with smooth curvature) achieves the higher lift than hydrofoil B (comprising several protrusions and hollows along the surface), specially at high reduced frequency. Although the frequency collected from two hydrofoils remains nearly the same near the leading edge and in the wake region, the high sub-frequency is evidently reduced for hydrofoil B in second and third hollows, due to the relatively stable trapped vortices. Then, the wake transition from the thrust-indicative to drag-indicative profile for hydrofoil B is also slower compared with hydrofoil A. Finally, it is observed that with the increase of the thickness, the lift/drag ratio decreases and the slow wake transition is detected for the thin hydrofoil, which is associated with the relatively low drag coefficient.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-22T03:55:04Z
      DOI: 10.1177/09544100221140632
       
  • Numerical analysis of aerodynamic characteristics of multi-pod hyperloop
           system

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      Authors: Muhammad Omer Mirza, Zaib Ali
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The Hyperloop system is a new and innovative mode of transportation in which high-speed pods move through near-vacuum tubes. The multi-pod Hyperloop Systems are essential for increased transportation capacity. In this study, a multi-pod Hyperloop System was analyzed using numerical simulations at different values of the distance between the pods (i.e., 2 L–3.5 L). The pressure and velocity flow fields and the aerodynamic characteristics of the pods were analyzed for four different flow speeds, that is, 100, 200, 300, and 400 m/s, using unsteady compressible flow conditions. The simulation results indicated that the pressure waves generated across the pods play a significant role in the determination of the aerodynamic characteristics of the pods. Increasing the distance between the pods results in the delay of the pressure wave interaction. The aerodynamic drag increases on the first pod with the increase in the distance between the pods due to an increase in the pressure gradient. In contrast, the aerodynamic drag decreases across the second pod with the increase in the distance between them. So, the distance between the pods is a critical factor that should be considered when designing the Hyperloop System with more than one pod.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-19T04:21:41Z
      DOI: 10.1177/09544100221137483
       
  • Aircraft parameter estimation using a novel hybrid
           

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      Authors: Tamas Pal, Mrinal Kaushik
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The neural network–based aircraft parameter estimation techniques have gained prominence in the last decade. Neuro–Gauss–Newton (NGN) technique is a widely used neural network–based algorithm. Although the NGN technique is useful for aircraft parameter estimation, it has some limitations. The present study is motivated by the limitations of the NGN method in estimating aircraft parameters, and hence, a new hybrid Luus–Jaakola/Hooke–Jeeves (LJ/HJ) method is proposed. The hybrid LJ/HJ method is based on two direct search methods: the Luus–Jaakola (LJ) method and the Hooke–Jeeves (HJ) method. In the hybrid LJ/HJ method, a global search of the minima of the error cost function is performed using the Luus–Jaakola method in the first phase. After that, the final solution is obtained using the Hooke–Jeeves method. The parameters estimated by the hybrid LJ/HJ method are compared with those estimated using the NGN method. The results obtained from the hybrid method are accurate, and unlike gradient-based optimization methods, the convergence issues are not observed during the estimation of parameters.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-19T03:23:42Z
      DOI: 10.1177/09544100221140980
       
  • Design optimization and analysis of HTHL suborbital spaceplanes propelled
           by hybrid rocket motors

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      Authors: Mingyang Xiao, Hao Zhu, Yuanjun Zhang, Pengcheng Wang, Guobiao Cai
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a design optimization and parameter analysis of a horizontal takeoff horizontal landing (HTHL) suborbital spaceplane propelled by a hybrid rocket motor (HRM) is proposed. Referenced by a prototype, an integrated design model, including the mass and shape estimation, HRM design, aerodynamic calculation, and trajectory simulation, is established. A series of long burning experimental tests in the reference article is adopted to modify the influence of nozzle erosion on HRM. After modification, the results of HRM design are well fitted with the test ones, which verified the precision of the modified model and revealed the importance of erosion effect on HRM performance. Then, the integrated design process is built and optimized by the multi-island genetic algorithm. The results indicated that the designed HRM-propelled suborbital spaceplane could achieve the target flight height under all the constraints. The parameter analysis (PA) based on optimum result is adopted to analyze the influences of design variables on the performance parameters of the HTHL suborbital spaceplane, and it also gives theoretical reference to the design optimization of the similar aerospace vehicles.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-18T11:20:33Z
      DOI: 10.1177/09544100221134164
       
  • Autonomous trajectory planning method for hypersonic vehicles in glide
           phase based on DDPG algorithm

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      Authors: Cunyu Bao, Peng Wang, Ruizhi He, Guojian Tang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An autonomous optimal trajectory planning method based on the deep deterministic policy gradient (DDPG) algorithm of reinforcement learning (RL) for hypersonic vehicles (HV) is proposed in this paper. First, the trajectory planning problem is converted into a Markov Decision Process (MDP), and the amplitude of the bank angle is designated as the control input. The reward function of the MDP is set to minimize the trajectory terminal position errors with satisfying hard constraints. The deep neural network (DNN) is used to approximate the policy function and action-value function in the DDPG framework. The Actor network then computes the control input directly according to flight states. Using a limited exploration strategy, the optimal policy network would be considered fully trained when the reward value reached maximum convergence. Simulation results show that the policy network trained using a DDPG algorithm accomplishes 3-dimensional (3D) trajectory planning during the HV glide phase with high terminal precision and stable convergence. Additionally, the single step calculation time of the policy network occurs in near real time, which suggests great potential as an autonomous online trajectory planner. Monte Carlo experiments prove the strong robustness of the implementation of an autonomous trajectory planner under aerodynamic disturbances.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-18T10:20:38Z
      DOI: 10.1177/09544100221138911
       
  • Performance evaluation of different micro vortex generators in controlling
           a flare-induced shock–boundary layer interaction

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      Authors: Tamizhazhi Korkkai Vendan Nilavarasan, Ganapati Narasimha Joshi, Ajay Misra, Chidambaranathan Manisankar, Shashi Bhushan Verma
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This study evaluates the ability of five micro vortex generator (MVG) geometries in attenuating the flow separation induced by an axisymmetric compression corner. Experimental and computational investigations were carried out at Mach 2 on a cone–cylinder–flare model, with a flow deflection angle of 24° at the cylinder/flare juncture. The MVG shapes considered were baseline ramp, trapezoidal ramp, split ramp, thick vanes and ramped vanes. A circumferential array of these MVGs having a device height (h) of 1.4 mm and an inter-device spacing of 10.5 mm (7.5 h) was introduced 50 mm upstream of the compression corner. Streamwise counter-rotating vortex pairs that originated from these devices created alternate bands of upwash and downwash regions in the incoming boundary layer, which resulted in suitable three-dimensional alterations of the separation region’s size. Furthermore, surface streamline visualizations showed that the vortices induced profound topological transformations in the separated flow structure. In the absence of MVGs, spectral analysis of the pressure signal obtained from the separation shock’s intermittent region revealed a relatively broadband dominant frequency range of 0.55 kHz–0.9 kHz. The MVGs did not cause any significant change in the dominant frequency, but made the bandwidth slightly narrower. Among the different MVG designs that were studied, the ramped vanes (RV) induced the most momentum augmentation in the near wall region and thereby caused the maximum downstream shift in the separation shock’s position.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-16T09:20:23Z
      DOI: 10.1177/09544100221139958
       
  • Effect of modifications to island shape and geometrical configuration on
           the external aerodynamics of a generic aircraft carrier

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      Authors: Marthamootil Philipose Mathew, Sidh Nath Singh, Sawan Suman Sinha, Rajgopalan Vijayakumar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The external aerodynamics of an aircraft carrier plays a vital role in the safe landing of aircraft during take-off and recovery. The hull, flight deck, and the island create a turbulent disturbance behind the aircraft carrier, leading to a simultaneous reduction in forward velocity and a downwash, which together create a sinking effect on the aircraft along its glideslope path. This phenomenon is known as the burble effect. It could potentially increase the pilot’s workload and strain their mental and physical faculties. Any design change that obviates or reduces the burble effect would potentially increase the probability of safely landing the aircraft on an aircraft carrier. There are only a few studies on the external aerodynamics of an aircraft carrier. The primary motivation of this study is to evaluate the effect of modifications to the island structure on the external aerodynamics of a generic aircraft carrier, especially the burble behind the carrier. The first part of the study pertains to the parametric changes to the aspect ratio of the island, that is, its length to width ratio and the consequent impact on the aerodynamics behind the carrier along the flight glide path. The second part of the study focuses on changing the geometry of the island by rounding the assumed cuboid island’s sharp corners, and evaluating its effect on the burble along the glideslope path of the aircraft. For the study, computational fluid dynamics (CFD) analysis on a generic aircraft carrier model has been carried out using the commercially available CFD solver Ansys FLUENT. The CFD studies have been validated by results of experiments conducted in a wind tunnel on the same generic aircraft carrier model. From the studies, it is seen that the aspect ratio of the island greater than one and rounding the sharp edges of the island have beneficial effects in reducing the impact of the burble behind the carrier.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-15T12:13:32Z
      DOI: 10.1177/09544100221138919
       
  • The effect of the blended blade and end wall three-dimensional profiling
           design on cascade

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      Authors: Jiezhong Dong, Wulin Chu, Xiangjun Li, Jinhua Lang, Zhengtao Guo
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Blended Blade and End Wall (BBEW), a passive control method, has been employed in the turbomachinery field and verified to improve compressor performance effectively. In this paper, a new profiling method, based on suction surface parameterization, is proposed to enhance the flexibility and three-dimensional characteristics of BBEW profiling. The new profiling method is applied to a high subsonic-speed and highly loaded compressor cascade. The aim is to investigate effective flow control rules and practical design guidelines under multi-operating conditions. First, the design method for the experiential formula is established, and the relationship between the profiling control mechanism and the profiling geometry feature is investigated in the entire three-dimensional design space. Then, comparing different radian pattern profilings on design and stall conditions, a series of quantitative analyses and flow field analyses are conducted to discuss flow control mechanism. The numerical results verify that the three-dimensional BBEW design brings a more positive effect on corner separation. The primary flow control rule is enhancing the driving force at the blade root, which can effectively increase the kinetic energy of the low-energy fluid in the corner region and reduce loss. However, design and stall conditions also have specific differences in the mechanism of loss reduction. It mainly focuses on the aggravation of mixing loss when the low-energy fluid obtains more kinetic energy on design condition, but the problem hardly exists in stall condition. Thus, a larger radian pattern is beneficial to controlling the flow on design condition, but the stall condition is the opposite.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-15T12:09:04Z
      DOI: 10.1177/09544100221138163
       
  • Multi-phase and dual aero/propulsive rocket landing guidance using
           successive convex programming

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      Authors: Sang-Don Lee, Chang-Hun Lee
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper aims to suggest a new landing guidance algorithm for reusable launch vehicles (RLVs) to enable generation of fuel-efficient trajectories based on successive convex programming. To this end, a dual aero/propulsive landing guidance problem is first formulated to fully exploit the additional moment generated by the aerodynamic control to reduce the propulsion demand required for attitude control. As the result of the aerodynamic landing phase could greatly affect the fuel-optimal trajectory during the vertical landing phase, the formulation is further extended to the multi-phase optimal guidance problem using state-triggered constraints. The proposed guidance strategy is then obtained by solving the formulated optimal control problem based on the successive convex optimization framework using an interior point method The main contribution of this study lies in forming new RLV landing guidance problems to get an optimal trajectory and transforming the corresponding nonconvex problem into a convex optimization problem by introducing appropriate combinations for convexification techniques. Additionally, this paper introduces several practical constraints, such as the maximum slew rate of aerodynamic control fins and nozzle angles, which are not considered in previous works. In this paper, the performance of the proposed method with the potential for online computation is investigated through numerical simulations.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-10T08:27:20Z
      DOI: 10.1177/09544100221138350
       
  • A novel interactive robust filter algorithm for GNSS/SINS integrated
           navigation

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      Authors: Bin Zhao, Qinghua Zeng, Jianye Liu, Chunlei Gao, Tianyu Zhao, Rongbing Li
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To solve the problem of Kalman filter (KF) performance degradation in unmanned aerial vehicle (UAV) applications, a novel interactive robust filter algorithm for GNSS/SINS integrated navigation is proposed in this paper. The strong tracking Kalman filter (STKF) is robust to uncertain system noise but is ineffective to abnormal measurement information. Based on the same performance index function with STKF, a measurement noise covariance matrix adaptive Kalman filter algorithm (MAKF) is presented, but it is ineffective under uncertain system noise. Furthermore, the interactive robust filter algorithm based on STKF and MAKF (IF-STKF-MAKF) is proposed, given the complementary characteristics of the above two filter algorithms. The STKF and MAKF operate in parallel based on the same system model. The filter probability of each filter is updated according to the likelihood function to perform output fusion and input interaction. The simulation and experiment results demonstrate that the IF-STKF-MAKF is effective and can achieve high estimation accuracy under both system noise anomalies and measurement information anomalies. In the vehicle experiment, the position accuracy of the proposed IF-STKF-MAKF method has been improved by more than 30% compared with KF, STKF, and MAKF. This method can also be extended to land vehicles, mobile robots, etc.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-10T07:03:18Z
      DOI: 10.1177/09544100221138133
       
  • Optimal transfer orbit design of spacecraft with finite thrust based on
           Legendre pseudospectral method

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      Authors: Lianghui Tu, Yuhao Wang, Chao Yan, Yang Yang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This article explores the application of the Legendre pseudospectral method to spacecraft orbital transfer with finite thrust optimization problem. Firstly, the model of the orbital transfer optimization control problem was established, while equations of motion were simplified based on some hypotheses. The performance was optimized to minimize the cumulative fuel consumption. The control variable was the thrust attack angle, and terminal state variable constraints included path angle, altitude, and velocity constraints. Then, the optimal control problem was transformed into a nonlinear programming problem (NLP) using the Legendre pseudospectral method. The dynamic optimization problem was transformed into a static parameter optimization problem. The state variables and control variables were selected as the optimal parameters at all collocation nodes. Lastly, the parameter optimization problem was solved using the SNOPT (Sparse Nonlinear Optimizer) software package. The SNOPT software package shows high convergence for a nonlinear programming problem. During the simulation, it was noted that the Legendre pseudospectral method is not sensitive to orbital transfer initial conditions. It was also observed that the optimal solutions of the orbital transfer optimization problem are fairly good in robustness. Therefore, the Legendre pseudospectral method is a viable approach to the spacecraft orbital transfer with a finite thrust optimization problem. The orbit optimization method proposed in this paper can also provide reference and guidance for solving other interplanetary orbital transfer optimization problems.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-10T06:33:59Z
      DOI: 10.1177/09544100221138164
       
  • Fault detection and diagnosis for liquid rocket engines with sample
           imbalance based on Wasserstein generative adversarial nets and multilayer
           perceptron

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      Authors: Lingzhi Deng, Yuqiang Cheng, Shuming Yang, Jianjun Wu, Yehui Shi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The reliability of liquid rocket engines (LREs), which are the main propulsion device of launch vehicles, cannot be overemphasised. The development of fault detection and diagnosis (FDD) technology for LREs can effectively improve the safety and reliability of launch vehicles, which has important theoretical and engineering significance. With the rapid development of artificial intelligence technologies such as machine learning and artificial neural network, data-driven FDD methods have gained increasing attention. However, the scarcity of engine fault samples limits the application of this methods. We proposed a method combining Wasserstein generative adversarial nets (WGANs) and multilayer perceptron (MLP) to perform FDD for LREs with sample imbalance. Wasserstein generative adversarial nets were trained using the fault data from the actual hot-firing ground test of a large LRE. Considerable fault data were generated to expand the data set to balance the ratio of positive and negative samples. Subsequently, the expanded data set was used to train the MLP for FDD of a large LRE. The results showed that the samples generated by the WGAN were authentic, confirming the application of the proposed method as a novel and effective tool for establishing a complete LRE fault database. Furthermore, the diagnosis times of the proposed method on five fault tests were advanced by 0.66, 15.82, 0.24, 0.14 and 1.08 s in relation to those of the conventional red-line cut-off system. Compared with support vector machine and adaptive threshold algorithm, the proposed method also performed better.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-09T05:49:08Z
      DOI: 10.1177/09544100221137975
       
  • Model updating and vibration control of membrane Antenna spacecraft based
           on on-orbit modal identification

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      Authors: Xiang Liu, Guoping Cai, Chaolan You, Saijin Yao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, on-orbit modal identification of membrane antenna spacecraft is investigated. Based on the modal identification results, dynamic model of the spacecraft is updated, and a vibration controller is designed. First of all, the rigid-flexible coupling dynamic model of the membrane antenna spacecraft is established by using Lagrange equation. Then, the covariance driven stochastic subspace identification (SSI-COV) method, which only relies on output measurements of the system under ambient excitation, is adopted to identify the modal parameters. By using the modal identification results, the model updating is performed based on sensitivity analysis, and vibration controller is designed to suppress the vibration caused by attitude maneuver based on the component synthesis vibration suppression (CSVS) method. Simulation results show that the SSI-COV method can identify the modal parameters of the membrane antenna spacecraft effectively, the updated dynamic model produces obvious improvements over the original model, and the vibration suppression effect of the CSVS controller is improved significantly after model updating.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-05T02:17:13Z
      DOI: 10.1177/09544100221135000
       
  • Design of contingency point return trajectory in the lunar orbit insertion
           phase for crewed lunar exploration missions

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      Authors: Lin Lu, Jianping Zhou, Haiyang Li, Hailian Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To satisfy the requirement of contingency rescue in the lunar orbit insertion phase for crewed lunar exploration missions, this paper designs the contingency point return trajectory. First, according to different failure situations of the main propulsion system in the lunar orbit insertion phase, different types of contingency return modes are analyzed and summarized. Second, considering the terminal constraints of point return, a calculation model of the contingency point return trajectory is established, and a serial optimization process is adopted to obtain a high-fidelity solution. Finally, a numerical simulation is used to verify the model. The simulation results indicate that this model can be applied to determine the contingency point return trajectories under different situations in the lunar orbit insertion phase and demonstrate the validity and feasibility of the trajectory calculation model proposed in this paper. The research conclusions can provide a reference for the design of contingency rescue schemes in the lunar orbit insertion phase for crewed lunar exploration missions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-04T07:59:31Z
      DOI: 10.1177/09544100221138131
       
  • Conceptual design of a third generation aerobatic aircraft

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      Authors: Zdobyslaw Goraj, Andrzej Frydrychewicz, Stanislaw Danilecki, Aleksander Olejnik, Łukasz Kiszkowiak
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents the development of an aerobatic aircraft including the influence of platform configuration on performance, elegance and safety of aerobatic manoeuvres. Several aircraft of different wing loadings were compared and the reduction of wing loading on manoeuvring slowdown was studied. Advantages of the biplane configuration influence on the desired properties of aerobatic aircraft were discussed in detail. Results of numerical simulations obtained for HARNAS-3 aircraft were compared with corresponding results received for EXTRA 300 aircraft. Some original design solutions for HARNAS-3, enabling easier control of this aircraft during the manoeuvring phase, were presented. Numerical simulations, wind tunnel tests and free flight experimental results for scaled-down HARNAS-3 models were presented, compared and discussed.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-04T02:42:43Z
      DOI: 10.1177/09544100221136327
       
  • Distributed containment formation control for multiple unmanned aerial
           

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      Authors: Bojian Liu, Aijun Li, Yong Guo
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper devotes to addressing the distributed containment formation control problem for multi-UAVs with collision avoidance and external disturbances. The proposed communication structure design algorithm enables the followers to form the pre-defined formation based on the containment control. Then, based on the information of the desired position for the followers, a novel Lyapunov function is designed to achieve global collision avoidance, and an adaptive backstepping containment control law is proposed. Moreover, by taking the advantage of deep reinforcement learning, a parameter optimization method is presented to balance the value of input signals and the performance of the controller. Finally, the simulation results demonstrate the superiority and effectiveness of the proposed algorithms.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-02T07:45:06Z
      DOI: 10.1177/09544100221135123
       
  • Velocity-free fixed-time output feedback attitude tracking control of
           rigid spacecraft

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      Authors: Zheng Yin, Zou Zhanjie, Yan Wang, Bintao Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper studies the problem of velocity-free fixed-time attitude tracking control for spacecraft. A new fixed-time sliding mode control method is proposed for the spacecraft attitude tracking control system. And, a novel fixed-time convergent sliding surface is designed based on the fixed-time control theory. In order to estimate the unmeasurable spacecraft information, the fixed-time observer was used to estimate the attitude information of the spacecraft. Combined with the above method, the fixed-time tracking controller is developed to guarantee the attitude tracking error of spacecraft converges to a small region within a fixed time. The fixed-time stability of the closed-loop system is proved based on the Lyapunov theory, and numerical simulations are presented to illustrate the effectiveness and superiority of the controllers.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-02T01:20:17Z
      DOI: 10.1177/09544100221133457
       
  • Insight into the significance of relative humidity on Nusselt number of
           crossflow heat exchangers with staggered elliptic tubes

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      Authors: Arshan Ahmed, Atta ul Mannan Hashmi, Fahad Rafi Butt, Zafar Bangash, Shahbaz Ghani, Imran Akhtar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Heat exchangers provide means to maintain the temperature of a system at its desired level. In this paper, numerical simulations of a heat exchanger with staggered arrangement of elliptical-shaped tubes have been performed to analyze its performance. Keeping the Reynolds number of dry and humid cooling air between 5000 and 20,000, the impact of relative humidity on the forced convection and the average Nusselt number is analyzed for a typical radiator cross-section. Numerical results indicate an increasing trend of the Nusselt number (up to 4.5%) with relative humidity. This variation becomes more pronounced when the capacity of air to absorb water increases with the same relative humidity but at higher temperatures.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-11-01T12:57:35Z
      DOI: 10.1177/09544100221135104
       
  • Barrier Lyapunov function based fixed-time control for automatic carrier
           landing with disturbances

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      Authors: Dapeng Zhou, Zewei Zheng, Zhiyuan Guan, Yunpeng Ma, Lin Ma
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper studies the automatic carrier landing controller design problem with output constraint and fixed-time convergence requirements. The proposed flight controller is separated into guidance, attitude control, and approach power compensation system. In each submodule, universal barrier Lyapunov function and fixed-time control scheme are applied in the controller design. In addition, adaptive estimation method is incorporated to improve the robustness to the external disturbances. The proposed controller ensures the position tracking error, attitude tracking error, and angle of attack tracking error not violate the predesigned boundaries, while the tracking errors will converge to a small set around zero in fixed-time. The output constraint and fixed-time convergence properties of the proposed controller improve the landing security to a narrow flight deck in a limited operation time. The simulation results verify the proposed controller in automatic carrier landing mission.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-31T04:58:05Z
      DOI: 10.1177/09544100221096022
       
  • Time-optimal moving target interception with impact angle constraint

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      Authors: Nikhil Kumar Singh, Sikha Hota
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The time-optimal guidance law with impact angle constraint to intercept a nonstationary nonmaneuvering target in three-dimensional (3D) space by Unmanned Aerial Vehicles (UAVs) is discussed in this paper. To achieve less computational complexity, the guidance law proposed here is based on the proportional navigation (PN) law existing in the literature. Three stages are used with different values of the Navigation gains of PN law to intercept the target moving in any given direction. To calculate the final position of each phase, a geometric based optimal path calculation technique has been adopted. Another important factor of this guidance law is that the lateral acceleration bound has also been taken into account in designing the guidance law. The simulation results show that the presented scheme performs better than the existing work in literature based on the Sliding Mode Control (SMC).
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-20T01:53:51Z
      DOI: 10.1177/09544100221133422
       
  • Adaptive coupled attitude-servo control for moving mass flight vehicles
           with high-mass-ratio

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      Authors: Zhitao Liu, Jianqing Li, Huan Zhou, Changsheng Gao, Wuxing Jing
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Moving mass flight vehicles (MMFVs) with high-mass-ratio suffer from a more severe nonlinear attitude-servo coupling than the traditional configurations that are under particle moving mass hypothesis. Therefore, the coupled attitude-servo control problem is investigated in this paper, and an adaptive backstepping sliding mode controller with extended state observers and neural-networks (ABSMC-ENN) is proposed. Based on the formulated control model with strict-feedback form, a sliding mode control law (SMC) with exponential reaching rate and a nonsingular terminal sliding mode control law (NTSMC) are combined to perform the fast and robust tracking of the command angle-of-attack. Considering the disturbances and uncertainties existing in the coupled dynamics, two nonlinear extended state observers (ESOs) are utilized to estimate the total disturbances online for compensation. To further enhance the adaptiveness and dynamic response performances of the controller in various flight conditions, two radial basis function neural networks (RBFNNs) are exploited to optimize the switching gains of the controller in real-time with performance indexes being the functions of tracking errors. Closed-loop stability of the whole system is proved via Lyapunov methodology. Comparison simulation studies considering multiple disturbances, various flight conditions, and different controllers successfully demonstrate the superiority of the ABSMC-ENN in robustness and adaptiveness.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-19T12:08:34Z
      DOI: 10.1177/09544100221133471
       
  • Frequency modulation analysis of solar array using genetic algorithm

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      Authors: Rui Zhu, Dong Jiang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, the optimal placement of prestress (OPP) is investigated for solar array frequency modulation using the genetic algorithm (GA). The purpose of OPP is to improve the solar array’s fundamental frequency and prevent coupling resonance between the solar array and the microwave imager. Prestress is applied to a solar panel by the tension actuators. For optimization producers, the finite element model is used to analyze the prestress configuration problem, which can be converted into the number of programming decision constraints. The automatic interactive updating calculation between MATLAB and finite element software is realized by programming. The GA is used to optimize the solution. Region detection is used, and the bad individuals can be eliminated directly to avoid fitness calculation and effectively improve the optimization efficiency. Simulations are conducted for a solar panel with four arrays. Single-, two-, and three-plate optimizations are investigated. Four optimization parameters include the abscissa value, ordinate value, the laying direction of the actuator in the global coordinate system, and the prestress magnitude. Results demonstrate that the fundamental frequency reaches the maximum at a horizontal layout of prestress after the frequency modulation. The optimal solution is obtained when the prestress is placed in No.2, No.3, and No.4 plates.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-19T10:10:02Z
      DOI: 10.1177/09544100221133867
       
  • Effects of cavity parameters on flame flashback phenomenon in a supersonic
           crossflow with a cavity flameholder

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      Authors: Tao Tang, Guoyan Zhao, Hongbo Wang, Mingbo Sun, Zhenguo Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, the cavity parameters of length-to-depth ratio, aft ramp angle, and nitrogen throttling positions are numerically studied by a Large Eddy Simulation (LES) combined with the Flamelet/Progress Variable (FPV) model, to investigate the inducing factors and formation mechanism of flame flashback. These numerical studies are validated and compared to our previous experiments. It can be observed from both the calculated and experimental flow field that the larger length-to-depth ratio, sharper aft ramp angle, and nitrogen throttling closer to the cavity strengthen the mixing of fuel wake and promote the jet penetration depth. Meanwhile, the separation of the boundary layer downstream of the cavity can be induced by the shear layer, acoustic oscillation, as well as nitrogen throttling. And the above favorable prerequisites enhance the heat release nearby, while the reverse pressure gradient causes the enlargement of the boundary layer separation in turn. Under this positive feedback, thermal choking is formed and drives the reverse propagation of the high-temperature flame. It is concluded that the downstream boundary layer separation induced by the changes of the cavity parameters is a prerequisite for the flame flashback, and the formation of the thermal choking is the main reason for the flame flashback.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-19T02:05:27Z
      DOI: 10.1177/09544100221133423
       
  • Aerodynamic modelling of flapping insect: A review

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      Authors: Mohd Faisal Abdul Hamid, Antonio Filippone
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A review of the aerodynamic modelling of insect flight is presented. This paper consists of two sections covering various aspects related to the development of flapping wing and research on the aerodynamic modelling of insect flight. First, we provide an overview of the nature of the flyers, including current issues and challenges related to the evolution of nature-inspired design. The second section discusses some of the techniques required to develop aerodynamic models, seeks to address issues and to identify appropriate aerodynamic modelling methods for the development of insect flight models. Experimental models of flapping wing insect are discussed, followed by numerical models. Finally, we highlight the development of prototypes in insect flight, on the design, sizing and classification of the flying insect prototypes.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-17T11:20:22Z
      DOI: 10.1177/09544100221134325
       
  • Jet mixing manipulation with asymmetric orientation of tabs

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      Authors: Aravindh Kumar Suseela Moorthi, Arun Kumar Perumal, Ethirajan Rathakrishnan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The jet mixing caused by two rectangular and triangular tabs of geometric blockage 2.5% each, separated by 90⁰ at the nozzle exit plane of a Mach 2 circular jet, in the presence of varying levels of expansion, corresponding to nozzle pressure ratio (NPR) 4–8, was investigated experimentally. The relative mixing promoting capability of these tabs was assessed. It is found that the rectangular tabs at 90⁰ interval retards mixing for NPRs 4, 5, and 6, and promotes mixing at NPRs 7 and 8. Comparison of the present result for rectangular tabs at 90⁰ interval with that of Arun Kumar and Rathakrishnan for 180⁰ interval shows that the mixing promoting capability of 90⁰ and 180⁰ intervals are comparable, at NPR 7. But at NPR 8, the mixing performance of rectangular tabs at 90⁰ interval is better than 180⁰ interval. For NPRs 7 and 8, the core length reduction due to rectangular tabs at 90⁰ and 180⁰ are 26% and 36%, and 28% and 26%, respectively. On the contrary, the triangular tabs at 90⁰ interval promote mixing at all NPRs of the present study. The mixing caused by triangular tabs at 180⁰ interval reported in literature is only marginally better than triangular tabs at 90⁰ interval studied in this work. For NPR 4, 5, 6, 7, and 8, the core length reduction caused by triangular tabs, at 90⁰ and 180⁰ intervals, are 24%, 58%, 69%, 80%, and 76%; and 38%, 65%, 77%, 87%, and 85%, respectively.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-13T11:01:37Z
      DOI: 10.1177/09544100221132653
       
  • Drag decomposition of a subsonic wing via a far-field, exergy-based method

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      Authors: Dimitrios K Logothetis, Pavlos K Zachos, Jean-Michel Rogero
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper focuses on the aerodynamic analysis and drag decomposition of an unpowered, low aspect ratio wing, using a far-field, exergy-based method. As opposed to traditional drag accounting methods, exergy balance provides insights into the amount of energy that can be potentially recovered off the body’s wake, which further translates into potential efficiency gains of the integrated engine-wing system. In this study, a far-field exergy balance method was used to determine the total drag of a three-dimensional wing. The far-field drag prediction was verified against near-field calculations. In addition, drag decomposition using exergetic terms was conducted to identify drag components that contain possibly recoverable energy. Such analysis can be subsequently used to educate the integration of a propulsion system to exploit the potentially recoverable wake energy and deliver an integrated engine-wing system with enhanced installed efficiency. The present methodology is a major step ahead in the application of far-field methods on three-dimensional wake domains and can potentially become a major enabler for optimal propulsion integration for future, novel aircraft-engine configurations.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-13T08:16:27Z
      DOI: 10.1177/09544100221132649
       
  • Chattering-free discrete-time sliding mode control for integrated missile
           guidance and control system

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      Authors: Xinming Wang, Di Wu, Jingang He, Jinpeng Zhang, Shihua Li
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      With the development and validation of flight control devices, electronic equipment is widely used in current flight vehicles, which results in a series of control signals in the discrete-time domain. However, many mature integrated guidance and control schemes are designed in the continuous-time domain, and some results of them may not be preserved in the discrete-time domain especially for the sliding mode control. To address this issue, a chattering-free discrete-time sliding mode control scheme is proposed for the integrated guidance and control systems of missiles. By applying the Euler’s discretization method, an approximated discrete-time model with matched and mismatched disturbances is first derived for integrated guidance and control system. Then, the estimates of the disturbances are obtained by using discrete-time generalized proportion integral observers. Integrating the estimated disturbances into the sliding mode variable, a discrete-time sliding mode controller is established by utilizing a modified chattering-free reaching law. The reachability of quasi-sliding mode band, states boundedness, and output convergence performance are analyzed rigorously. Finally, comparative numerical simulations are conducted to verify the effectiveness of the proposed control scheme in the presence of unknown target maneuvers and parameter uncertainties.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-11T10:43:53Z
      DOI: 10.1177/09544100221131212
       
  • Spark range data reduction using a Gauss collocation method

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      Authors: Bradley T Burchett
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A new method is proposed for reducing spark range data using a Gauss pseudospectral collocation. Existing methods use numerical integration to propagate the differential equation model and its sensitivities forward in time. Here, a collocation method is used to transcribe the differential equations into algebraic ones that are easily solved. Realizing that the auxiliary equations used to find model sensitivities are linear, a second transcription renders a set of linear algebraic equations that solve exactly for the needed sensitivities without iteration. Thus, measurement sensitivities with respect to initial conditions and aerodynamic parameters are easily found through solution of a set of linear algebraic equations. The method is demonstrated on a set of actual data from the M898 155-mm projectile. For models using fixed-plane coordinates, and only the 10 most influential aerodynamic coefficients, the new method produces results that rival established commercial codes in accuracy.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-07T02:37:52Z
      DOI: 10.1177/09544100221130382
       
  • A fault detection method for Auxiliary Power Unit based on monitoring
           parameters selection

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      Authors: Heng Jiang, Jing Cai, Zhirong Zhong, Jiachen Guo, Hongfu Zuo
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Auxiliary Power Unit (APU) is an indispensable component utilized in modern aircraft, which provides electrical and pneumatic power to the aircraft independently. What’s more, APU can help the main engines restart in case of main engine failure during flight. Thus there exists the need of APU monitoring. However, APU has not received sufficient attention in maintenance due to its relatively low cost and safety requirements compared to main engines. Line maintenance shows that APU is likely to fail in the start stage. Based on the Quick Access Recorder data supported by the airline, a fault detection method for APU is proposed in this paper. In order to improve the accuracy of fault detection, feature selection is carried out firstly to determine the optimal subset of monitoring parameters by Recursive Feature Elimination. Then fault detection is carried out by Support Vector Machine. Results show that Exhaust Gas Temperature is the most effective index among all monitoring parameters, and feature selection has a significant improvement on the accuracy of fault detection, which means higher accuracy with less monitoring cost. The method proposed in this paper also disposes that some monitoring parameters should be paid more attention in terms of the condition monitoring of APU.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-03T10:09:43Z
      DOI: 10.1177/09544100221130803
       
  • Differential flatness-based pseudospectral optimal control of
           six-degrees-of-freedom aircraft and its issues

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      Authors: R Sandeepkumar, Ranjith Mohan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The advent of efficient numerical algorithms and powerful computing resources have made real-time optimization a reality. However, for systems like 6DoF aircraft, the problem remains challenging due to the complexity and fast dynamics of the system. Smaller optimization problems with fewer constraints can be obtained from a differential flatness-based optimization scheme. This paper proposes a flatness-based nonlinear model predictive controller (NMPC) for a 6DoF aircraft to improve computational time. However, it is difficult to tell in advance if flatness-based NMPC can outperform the simultaneous NMPC with many variables and constraints. This is because there is a trade-off between loss in convexity and an increase in nonlinearity with a dimension reduction. In addition, nonlinear optimization solvers like IPOPT can exploit the underlying sparse structure of the optimization problems from simultaneous NMPC to compute solutions efficiently. Hence, a comparative study between flatness-based and simultaneous nonlinear model predictive control is necessary to assess the computational performance. Results are presented with discussions on solve time, numerical conditioning, convergence, convexity, and solve success rates of the optimization problem. The discussions presented can be extended to other systems to study the effectiveness of flatness-based optimization in a systematic manner. In addition, pseudospectral knots are explored in the paper, which improves sparsity and numerical conditioning of flatness-based optimal control problems.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-02T12:49:01Z
      DOI: 10.1177/09544100221112724
       
  • Computational study of hydrogen and air co-flow jets mixing in
           dual-combustor ramjet in presence of ramp shock generator

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      Authors: MohammadKazem Rostamian, Soroush Maddah, Yasser Rostamiyan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Flame stabilization distribution and efficient fuel mixing are highly significant in the performance of ramjet engine. In this paper, numerical studies are done to investigate the supersonic combustion of hydrogen and air co-flow in presence of the ramp edge. In this study, flame maintenance and combustion formation in a dual-combustion ramjet engine are fully investigated. The primary emphasis of this work is to disclose the impact of produced shocks due to the existence of ramp edge on the structure of fuel and air-jet immediately downstream of injector. The shock interactions of two different angles (10 deg and 30 deg) of the ramp edge are investigated. Favre-averaged conservation equations are considered for the simulation of compressible flows inside the combustor. Various mechanisms expressing the flame spreading characteristics are also examined. Depending on the angle of the ramp edge, the produced shock waves influence on size and strength of vortices. Our findings also show that high angles of ramp edge augment the fluctuation of the vortices by the splitter and consequently, fuel mixing enhances in the combustion chamber of ramjet engine. Our findings also confirm that the similar jet pressure would be more effective on the vortex production downstream of the splitter. The application of ramp edge with angle of 30 deg would increase average momentum thickness of the mixing layer up to 55%.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-02T09:47:13Z
      DOI: 10.1177/09544100221130384
       
  • Sliding mode control based impact angle constrained guidance with
           predefined convergence time

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      Authors: Kakoli Majumder, Shashi Ranjan Kumar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes predefined-time convergent guidance schemes that can drive the pursuer on a collision course corresponding to the target interception from a pre-specified impact direction, irrespective of initial engagement geometries. The target interception at the desired impact angle is first transformed into a problem of controlling the line-of-sight angle and its rate. Then, guidance commands are derived using sliding mode control (SMC) to ensure the convergence of corresponding errors to zero within a predefined time. A nonlinear disturbance observer is used to estimate the target’s maneuver, and the estimation error is treated as an uncertainty while rejecting its effect by virtue of SMC. Guidance commands are also derived for the case where the target maneuver is completely unknown except for its upper bound. It was shown that the gain could be selected based on the maximum bound on target maneuver to enforce sliding mode on the chosen surface, and thus guarantees target interception at a pre-specified impact angle, provided the closing speed of the engagement is positive. Owing to the use of a nonlinear framework while deriving pursuer guidance commands, the proposed guidance strategies remain valid even for engagements with large initial deviations where schemes based on linearized dynamics may fail or have degraded performance. The efficacy of the proposed guidance methods is validated through simulations for the pursuers having constant speed and time-varying speed, for various engagement geometries. The results of proposed strategies are compared with those of existing guidance and shown to be superior.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-10-01T09:02:23Z
      DOI: 10.1177/09544100221120160
       
  • Aircraft trajectory generation and control for minimum fuel and time
           efficient climb

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      Authors: Salahudden Salahudden, Harshal Vitthal Joshi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a novel approach for generating the best possible climb trajectory that ensures minimum fuel and time efficient climb. The problem is first formulated using standard steady climb equations, which generate a unique combination of flight velocity and flight path angle at each altitude. A possible scenario, such as air density, mass, available power, and required powered variation with altitude, is taken into account when defining the problem. Thereafter, sliding-mode-based trajectory tracking control is formulated with its design procedures, system stability with applied control inputs, finite-time convergence analysis, and complete architecture. A Hansa-3 research aircraft is considered as an example model to demonstrate the work. The findings of generated trajectory are then produced and discussed. In order to follow the design trajectory and achieve the same, the sliding-mode-based control command is supplied. The novelty of the present work lies in proposed strategy of trajectory generation, wherein the aircraft path and velocity are found out to make the fuel and time efficient climb possible. Subsequently, robust control law is developed which shows the applicability of the proposed work on autopilot. The results show that the proposed controller not only controls the aircraft but is also able to follow the design trajectory with minimal errors. To further explore the impact of aircraft mass on climb performance, repeated set simulation is carried out. The outcome is compared with conventional climb, which promises its practical implementation since the proposed solution is simple and compatible to integrate with the existing aircraft autopilot.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-28T07:01:59Z
      DOI: 10.1177/09544100221126567
       
  • Suboptimal attitude tracking control law and eigenvalue analysis for a
           near-space hypersonic vehicle based on Koopman operator and stable
           manifold method

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      Authors: Peichao Mi, Qingxian Wu, Yuhui Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes a novel strategy to design a suboptimal attitude tracking control law for a near-space hypersonic vehicle (NSHV) based on the Koopman operator and stable manifold theory. The nonlinear vector field of the NSHV attitude model is locally Lipschitz continuous and can be approximated by a high-dimensional linear system over a compact set. Linear and nonlinear parts of the attitude dynamics are determined based on this system. Subsequently, the stable manifold theory is applied to determine the unconstrained approximated optimal control law that is used to further consider the control input constraints of the NSHV attitude model. The suboptimality of the control law is analyzed, and the local exponential stability of the closed-loop system with input constraints is proven. Furthermore, the eigenvalues for the closed-loop nonlinear attitude error dynamics are analyzed. After the control input saturation, the nonlinear closed-loop error dynamics of the NSHV can be approximated by a high-dimensional linear system with a minimal dimension. The eigenvalues of this linear system indicate the stability and time response characteristics of the attitude error dynamics of the NSHV. The numerical simulation results demonstrate the effectiveness and suboptimality of the proposed attitude tracking control law and workflow of the eigenvalue analysis.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-28T05:02:12Z
      DOI: 10.1177/09544100221125963
       
  • Updating multi-fidelity structural dynamic models for flexible wings with
           feed-forward neural network

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      Authors: Yanxin Huang, Weihua Su
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In multidisciplinary design optimization of aerospace structures (e.g., a flexible wing), it may be convenient and practical to break such a complex problem into multi-fidelity, multi-stage design problems. Structural model updating is needed in multi-fidelity, multi-stage optimizations to ensure the consistency of models with different fidelity. However, due to the inequality in structural parameters, there exists a fundamental difficulty in the model updating from a lower fidelity model to a higher fidelity model. In this paper, a feed-forward neural network is applied to determine the structural dynamic characteristics of a higher fidelity model based upon a lower fidelity model. The feasibility of this approach is demonstrated by updating beam-like wings to a thin shell-based model and a one-cell wing box model, respectively. The quality and accuracy of model updating using the proposed method are also discussed regarding the neural network structure and sample size.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-27T07:51:12Z
      DOI: 10.1177/09544100221128998
       
  • Robust nonlinear guidance strategies for survival of cooperating unmanned
           aerial vehicles against pursuing attackers

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      Authors: Naveen Kumar S, Rohit V Nanavati, Shashi Ranjan Kumar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, cooperative guidance strategies for the survival of cooperating team of two unmanned aerial vehicles (UAVs) against two attackers are proposed. The guidance schemes are designed under the assumptions that each UAV is being pursued by one attacker without cooperation with other attacker. The guidance schemes are designed to combat attackers guided either by proportional navigation (PN) or augmented PN guidance methodologies. The attackers are lured onto a collision course with each other such that intra-attacker interception is achieved before the target UAVs are captured. Sliding mode control techniques are employed to satisfy the sufficiency conditions for the survival within a finite time. Due to the nonlinear framework used for guidance design, the proposed strategies remain effective even for the engagements with large heading angle errors. Numerical simulations are presented to demonstrate the effectiveness of the proposed guidance strategies under various engagement geometries.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-22T11:11:32Z
      DOI: 10.1177/09544100221115238
       
  • Experimental and computational investigations of aerodynamic
           characteristics of a finite rectangular wing-in-ground effect

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      Authors: Ravindra A Shirsath, Rinku Mukherjee
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Wind tunnel experiments are carried out on a 3D wing-in-ground effect at pre- and post-stall angles of attack at a relatively low Reynolds number, Re ≈ 8.8 × 104. The rectangular wing, aspect ratio, AR = 6.4 used in the present work has a symmetric airfoil section, NACA0012 and is studied at different ranges of ground proximity and also compared to a wing of cambered airfoil section, NACA4415 not in ground proximity. Unsteady and time-averaged six-component aerodynamic characteristics, coefficients of Lift, Drag, Side forces, Pitch, Roll, Yaw moments at several angles of attack in the range – 8° < α < 18° are reported. Aerodynamic efficiency and drag polars are studied in lieu of ground proximity at several angles of attack. Effect of ground proximity on the occurrence of stall and [math] is studied. Numerical calculations using steady-state CFD are also made for quantitative comparison. The effect of ground proximity on span-wise pressure distribution and induced velocity in the vicinity of the wing is also discussed in detail.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-21T11:06:53Z
      DOI: 10.1177/09544100221114700
       
  • Turbofan engine performance prediction methodology integrated
           high-fidelity secondary air system models

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      Authors: Xuesen Yang, Menghua Jian, Wei Dong, Qiannan Xu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This research studies the performance of an ultra-high bypass ratio turbofan engine, and specifically its secondary air system (SAS). A co-simulation methodology is explored whereby a high-fidelity SAS model and an engine performance code featuring flexible modules can be coupled and interactively executed. The percentage of bleed flows and boundary conditions for the SAS are updated at each iteration step. For this purpose, a SAS model including different elements is developed. Furthermore, a commercial computational fluid dynamics (CFD) solver is adopted to capture the complex flow field in the pre-swirl system. The credibility of cycle calculation and SAS elements is validated by comparing with publicly available data. Subsequently, an elaborately designed SAS is modeled and co-simulated with the AGTF30 engine using a flow network simulation method. The coupling effect between the engine performance and the SAS is studied for eight different flight conditions. The correlation and prediction of engine performance due to seal clearance change is presented. The co-simulation approach clarifies the mutual interactions between the engine overall parameters and the SAS. The results reveal that the enhanced flow network model can improve the simulation accuracy of engine performance over a wide range of operating conditions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-21T09:31:21Z
      DOI: 10.1177/09544100221117416
       
  • Measurement of flow fluctuations induced by a dielectric-barrier-discharge
           plasma actuator using hot-film sensors

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      Authors: Abbas Daliri, Mohammad Javad Maghrebi, Mohammad Reza Soltani
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Hot-film sensors have been used to measure the boundary-layer fluctuations and subsequently to determine the boundary-layer states. In this paper, it is proposed to use hot-film sensors as a tool to measure the effects of plasma-induced ionic wind on the boundary-layer fluctuations which can be used to find the influence of the plasma actuator far downstream of the actuator. Time history and frequency response of the hot-film output voltage are investigated to explore the effects of plasma-induced wind downstream of the actuator. Also, the effects of the peak-to-peak voltage of a DBD plasma actuator on the fluctuations of the hot-film output voltages are discussed. It is showed that as far as the effects of ionic wind can be sensed by the hot-films, the control authority of the actuator is higher. It is concluded that induced velocity in the vicinity of the plasma actuator alone does not indicate the control authority of the plasma actuator.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-20T04:24:30Z
      DOI: 10.1177/09544100221127462
       
  • Bounded distance control for Multi-UAV formation safety and preservation
           in target-tracking applications

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      Authors: Aditya Hegde, Jasmine Jerry Aloor, Debasish Ghose
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The notion of safety in multi-agent systems assumes great significance in many emerging collaborative multi-robot applications. In this paper, we present a multi-UAV collaborative target-tracking application by defining bounded inter-UAV distances in the formation in order to ensure safe operation. In doing so, we address the problem of prioritizing specific objectives over others in a multi-objective control framework. We propose a barrier Lyapunov function-based distributed control law to enforce the bounds on the distances and assess its Lyapunov stability using a kinematic model. The theoretical analysis is supported by numerical results, which account for measurement noise and moving targets. Straight-line and circular motion of the target are considered, and results for quadratic Lyapunov function-based control, often used in multi-agent multi-objective problems, are also presented. A comparison of the two control approaches elucidates the advantages of our proposed safe-control in bounding the inter-agent distances in a formation. A concluding evaluation using Robot Operating System simulations illustrates the practical applicability of the proposed control to a pair of multi-rotors visually estimating and maintaining their mutual separation within specified bounds, as they track a moving target.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-19T09:38:49Z
      DOI: 10.1177/09544100221125970
       
  • Experimental method for the planar landing of a three-legged asteroid
           probe: The effects of asymmetric configuration and element forces

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      Authors: Canhui Yin, Qiquan Quan, Dewei Tang, Peter Schiavone, Zongquan Deng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Focused on an asteroid probe with three-legged cushioning, this paper discusses the effects of the asymmetric configuration and the element forces form of the planarized cushioning mechanism on the method for developing the landing experiment. The main objectives are to present an accurate experimental analysis of the planar landing and to facilitate the construction of a micro-gravity experimental platform through the theoretical analysis in advance. Probe models based on the planar symmetric and asymmetric configurations of the cushioning mechanism were constructed and their parametric characterization was determined. Mathematical models of the element forces on cushioning legs were established and differences between each set of corresponding element forces were analyzed. Then, dynamics models explaining the landing process were established. On this basis, the maximum initial safe attitude angle and the change process of the attitude variables were researched. The results revealed that the asymmetric configuration greatly reduced the safety margin of the attitude angle and it was determined by the M-R(I) landing as 23°. In addition, the simplified version of the ground friction force could be employed for developing the experiment at the initial attitude angle of 20°, but it affected the results at the initial attitude angles of 0°, 5°, and 10°. At the initial attitude angle of 20°, which is more significant as the critical condition for dangerous landing, the normal footpad-ground contact of the merged leg could adopt the same stiffness coefficient as that of the real leg to facilitate the experimental design without affecting the experimental results.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-17T01:25:32Z
      DOI: 10.1177/09544100221123863
       
  • Assessment of the combustion chambers' atmospheric test data

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      Authors: Maziar Karam Ghareh Gheshlaghi, Amir Mahdi Tahsini
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Due to the complexities of the turbulent reacting flows in the combustion chamber of the turbo-engines, despite significant advances in the computational fluid dynamics, the experimental investigations are still very useful in design and optimization processes. On the other hand, the operating conditions of the combustion chambers are such that they have high inlet pressures and temperatures, so providing these conditions for the considered air flow in the combustion chamber is very complex and expensive. Therefore, the development of low pressure test stands has been considered for decades, and the atmospheric tests are utilized in many research centers and industries related to the turbo-engines. In the present study, using numerical simulations, the effect of pressure on the flame shape and pollutants is investigated and the validity of the results of atmospheric tests is analyzed. Here, an in-house developed program is used to solve the governing equations using the finite volume method. The results show that the flame shape significantly varies at low pressures compared to the operating conditions, and the atmospheric test data are not reliable enough.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-16T02:09:56Z
      DOI: 10.1177/09544100221127517
       
  • Multi-stage trajectory planning of dual-pulse missiles considering range
           safety based on sequential convex programming and artificial neural
           network

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      Authors: Chaoyue Liu, Cheng Zhang, Fenfen Xiong, Jin Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An algorithm based on sequential convex programming and artificial neural networks is proposed to solve the multi-stage trajectory planning problem of dual-pulse missiles considering range safety. Besides nonlinear dynamics and constraints, the dual-pulse missile introduces many discrete optimization variables (such as the ignition time of the second-stage thrust), and the algorithm needs to consider throwing the engine off to a safe location to ensure range safety, which makes trajectory planning for the dual-pulse missile more difficult to solve. In this study, the whole trajectory is first divided into four stages according to the working characteristics of the dual-pulse engine. Second, three new control variables are introduced to realize nonlinear dynamics convexification, and the relaxation technique is used to relax the constraints between the control variables to avoid non-convexity. Then, a range prediction function is designed to predict the landing location of the engine in real time. To improve the real-time prediction speed, an artificial neural network is further used to fit the range prediction function. Finally, an algorithm combining sequential convex optimization and an artificial neural network is proposed to solve the multi-stage trajectory planning problem of dual-pulse missiles accurately and rapidly. By comparing with pseudospectral method, two trajectory planning cases are solved by simulation, and the effectiveness and rapidity of the proposed method are verified.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-15T07:42:08Z
      DOI: 10.1177/09544100221127058
       
  • Stagnation heat flux estimation in spherically blunt axisymmetric
           hypersonic models

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      Authors: Kiran J Irimpan, Viren Menezes
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Hypersonic flows have high heat transfer rates, and their management is essential to avoid detrimental effects. Since accurate prediction and measurement of heat flux in hypersonic test facilities are complicated, heat flux at the stagnation point is mostly estimated using Fay and Riddell formulation with Newtonian tangential velocity gradient approximation. Although it is relatively accurate and reliable, some errors creep in due to incompetent modelling of the tangential velocity gradient. This article studies the applicability of Olivier's tangential velocity gradient formulation for a sphere in the estimation of stagnation heat flux for spherically blunt axisymmetric hypersonic models. Oliver’s estimation accurately models the tangential velocity gradient of spherically blunt axisymmetric hypersonic models as the heat flux estimates deviated only by approx. 2%–4% from the measured heat flux. A simplified model for tangential velocity gradient using Shock Standoff Distance and density ratio is also derived and tested for accuracy.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-07T11:55:51Z
      DOI: 10.1177/09544100221124799
       
  • Remotely piloted aircraft system flight-plan processing from a risk-based
           methodology

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      Authors: Javier A Pérez-Castán, V Fernando Gómez Comendador, Rosa M Arnaldo Valdés, Álvaro Rodríguez-Sanz, Cristina Altemir Rey
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The integration of Remotely Piloted Aircraft System (RPAS) in non-segregated airspace is one of the most demanding challenges that the aviation community must face in the years ahead. This article develops the flight-plan processing from a risk-based methodology. The risk-based methodology is underpinned by an in-depth safety analysis throughout the three temporary horizons of the Air Traffic Flow and Capacity Management system: strategical, pre-tactical and tactical. The flight-plan processing demands different measures depending on the temporary horizon. The measures mean geographical restrictions (airways or air corridors segregated for RPAS) and temporary restrictions (periods in which RPAS cannot operate). Both restrictions ensure that RPAS operation is safe and do not generate interactions with conventional aircraft. The last goal of this approach is to provide the required information to the RPAS operator based on the information available from the Network Manager (NM). The communication and information flow between the RPAS operator and the NM are detailed to validate flight-plan processing. If the initial flight plan is not affordable, the NM provides modifications during the flight-plan re-processing. The methodology is applied in the Spanish upper airspace. The results confirmed the validity and leeway of the flight-plan processing, although its implementation demands further improvements based on air traffic flow and path uncertainty.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-07T11:41:40Z
      DOI: 10.1177/09544100221125348
       
  • Dynamics simulation of a folding wing unmanned aerial vehicle with the
           parachute system assisted launching

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      Authors: Hangyue Zhang, Yanchu Yang, Rong Cai
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper mainly focuses on a series of dynamic problems caused by a small folding wing Unmanned Aerial Vehicle (UAV) with a parachute system assisted launched from the high-altitude balloon platform. The simulation contents are the four-stage motion processes of the “parachute-UAV system” after separation from the balloon platform, including the straightening stage, the inflation process, the stable descend under the influence of the wing deployment action, and the trajectory leveling of the UAV. The “parachute-UAV system” is equivalent to a multi rigid body connection structure. We introduce the straightening length parameter and the wing deployment angles based on the Kane method to establish the dynamic model. And we choose the inflation time method to simulate the parachute deployment process and the flat plate high angle of attack model to describe the wing aerodynamic force. In the simulation, we compare six launching processes of different wing deployment time periods and obtain the separation state of each UAV when cut from the parachute. We adopt the Radau Pseudo-Spectral method to calculate the leveling trajectory of six UAVs. This paper is an engineering application research study and can provide a simulation reference for the launching test of the balloon-borne folding wing UAV system.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-06T10:23:37Z
      DOI: 10.1177/09544100221124712
       
  • Three-dimensional enclosing control for stratospheric airship to
           circumnavigate a moving target

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      Authors: Yang Sun, Ming Zhu, Tian Chen, Zewei Zheng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper addresses the problem of a stratospheric airship flying around a time-varying velocity moving target in a three-dimensional space under external disturbance. In order to achieve a spiral shape circumnavigation around the moving target, it is necessary to keep the same altitude as the moving target with time-varying height vertically while keeping a fixed circle radius around the moving target at the horizontal plane. First, based on the air current estimator, we design different guidance laws for different target tracking methods on the horizontal and vertical planes respectively, which can obtain the expected velocity and the expected angular velocity. Second, an adaptive backstepping attitude controller to track the desired yaw rate is introduced by estimating the boundaries of dynamic couplings and unknown disturbance. Finally, a velocity controller is added to track the desired velocity. Numerical simulations show the validity of this algorithm.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-06T09:58:15Z
      DOI: 10.1177/09544100221119948
       
  • Effects of crosswinds and tip configurations on the initial phase of
           wingtip vortex evolution

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      Authors: Zeyu Zhang, Dong Li, Ziming Xu, Jinyan Cai, Jiaolin Cui
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Wingtip vortex is the initial phase of aircraft wake flow that jeopardizes flight safety. Previous studies have focused on the effect of incidence angle on tip vortex flow; thus, investigations on tip vortex in the roll-up stage under crosswind conditions are limited. In the present study, two NACA0012 wings with different tip shapes (round and square) were numerically analyzed to explore the effects of wingtip configurations on tip vortex. In addition, the effects of crosswinds on wingtip vortex evolution were also investigated. It was found that sharp edges of the square wingtip generated a multi-vortex system, resulting in a larger turbulent wake vortex core radius. The lift and vortex strength of the square wingtip were 23% higher and only 12% stronger than those of the round wingtip, respectively. Furthermore, crosswinds changed both the pressure distribution and the vortex structure. Crosswinds made the flow field unstable; hence, upwind lower edge vortices of the square wingtip burst earlier and merged faster. Consequently, the tightness of the upwind vortex of the square wingtip increased, and the corresponding vortex strength was enhanced. The downwind vortex of the square wingtip was weakened by 2.7% under a crosswind velocity of 4 m/s, whereas the downwind tip vortex of the round wingtip was strengthened under the same conditions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-06T06:06:15Z
      DOI: 10.1177/09544100221123868
       
  • Inhibition mechanism of static pressure circumferential double-peak
           distribution using a recirculation device for a centrifugal compressor

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      Authors: Botai Su, Ce Yang, Hanzhi Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The asymmetric volute structure in the turbocharger centrifugal compressor causes a static pressure circumferential double-peak distribution (PD-DP) at small flow rates and affects the circumferential stall position near the impeller inlet. In this study, a recirculation device was added to a prototype compressor, and the effect of the recirculation flow on the PD-DP was studied to reveal the difference in the PD-DP formation mechanism with and without the device. In addition, the influence of the PD-DP difference on the compressor flow stability was investigated. The results show that the PD-DP generated various pressure gradients between the front and rear slots of the recirculation device at different circumferential positions, resulting in a double-peak distribution in the recirculation flow rate. When the recirculation airflow flowed back into the impeller inlet, the two recirculation flow rate peaks were near the circumferential positions occupied by the two static pressure peaks in the prototype compressor. Therefore, the pressure distortion degree near the impeller inlet could be inhibited, weakening the difference in the deflection degree of the tip leakage flow (TLF) in each compressor passage. It should be noted that the circumferential positions with more prominent variation in the TLF corresponded to the passages with more serious flow deterioration in the prototype compressor, and the blockage of these passages near the inlet was reduced to a greater extent, which could better improve the flow stability of the compressor.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-06T04:47:30Z
      DOI: 10.1177/09544100221125001
       
  • Innovative design of modular pantograph tensegrity deployable cylindrical
           reflectors

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      Authors: Shuxin Zhang, Jing Ye, Shunji Zhang, Jingli Du
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To solve the problems of high areal density and low packaging ratio in available deployable cylindrical reflector antennas, an innovative design concept named the modular pantograph tensegrity deployable cylindrical reflector is proposed. The innovative design mainly consists of a pantograph tensegrity deployable truss, flexible cable nets, and reflective wire mesh surface. Based on the modular design concept, the pantograph tensegrity deployable truss can realize synchronous deployment in both parabolic and cylindrical directions. Compared with two typical deployable cylindrical reflectors, the proposed design has the advantages of lower areal density and higher packaging ratio. Simulations of performance analysis demonstrate the benefits of the innovative design.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-09-04T10:38:02Z
      DOI: 10.1177/09544100221124886
       
  • Design studies on NAGIC flowfield with application to integrated
           irregular-shaped supersonic inlet

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      Authors: Hang Zhou, Zhiguang Jin, Shiyu Deng, Xiaosong Tang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Fighters have increasingly demanding performance on both aerodynamic and stealth. To adapt the design requirement of various irregular-shaped supersonic inlets integrated with flat fuselages, a design method for non-axisymmetric generalized internal conical (NAGIC) flowfield is discussed and then developed. By osculating axisymmetric flow concept and method of characteristics, the developed supersonic NAGIC flowfield can be inversely designed with arbitrary capture curves, controllable incident/terminal shock wave geometries, and post terminal shock wave pressure. Employing the streamline tracing technique, a set of external-compression inward-turning inlets with triangle-like flat capture shapes for supersonic stealth fighters are obtained to verify the design method. The study find that the internal contraction ratio and flow distortion of the inlet are reduced significantly by replacing the weak reflected shock wave in the original hypersonic NAGIC flowfield with a strong one. Thus, the compatibility between inlet and engine is improved in a relatively wide range. In addition, the irregular-shaped curved-compression inlet has high mass ratio and total pressure recovery ratio with negligible cross flow and uniform flow at throat. The performance of inlets with complex configurations can be further improved by matching the entrance geometries of basic flowfields and inlets.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-29T03:01:42Z
      DOI: 10.1177/09544100221123735
       
  • Experimental investigation on the flame stabilization modes of liquid
           kerosene in a cavity-based scramjet combustor

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      Authors: Xipeng Li, Weidong Liu, Yu Pan, Ning Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The flame stabilization modes of liquid kerosene is investigated in a model scramjet combustor with flight condition of Ma 6. The effects of equivalence ratio and cavity configuration schemes on the flame stabilization modes are studied. Flame propagations and the evolution of the flow field from the ignition to the establishment of stable flame in the supersonic flow are acquired through high-speed photography and schlieren photography. Only cavity-recirculation-region stabilized combustion can be obtained in the single-cavity scramjet combustor. The intensity of combustion is weak and is termed as local ignition with low combustion efficiency. In the tandem-cavity scramjet combustor, the flame stabilization mode is largely determined by the total equivalence ratio. The flame could spread into the mainstream and even propagate against the supersonic flow as the equivalence ratio increases. The positive feedback mechanism between combustion and precombustion shock train is responsible for the evolutions of the flame stabilization modes, where the interactions between shock waves and turbulent boundary layer play a key role in the flame propagation process. The large-scale eddies in the shear layer of the upstream cavity shed at the cavity aft wall and could enhance the turbulent levels of the incoming flow of the downstream cavity. Consequently, an intense kerosene flame can be ignited in the tandem-cavity combustor. The flame could not spread to the mainstream in the single-cavity combustor due to the lower turbulence level weakening the interaction of combustion products in the recirculation zone with unburned reactants in the supersonic flow.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-29T01:20:16Z
      DOI: 10.1177/09544100221123895
       
  • A 6-DOF extended state observer–based adaptive generalized super
           twisting algorithm of fault-tolerant control for coupled spacecraft with
           actuator saturation

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      Authors: Yafei Mei, Kejie Gong, Ying Liao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper aims to address an integrated relative attitude and position fault-tolerant control strategy between a follower spacecraft and a leader spacecraft for coupled spacecraft tracking maneuver in the case of inertia parametric uncertainties, external disturbances, actuator failures, and saturation. The coupled rotational and translational kinematics and dynamics of the rigid spacecraft are derived on the Lie group SE(3), where the actuator failures and saturation are taken into account. Then, a 6-DOF extended state observer is proposed by using terminal sliding mode technique to estimate the lumped disturbance in finite time. An adaptive generalized super twisting algorithm of fault-tolerant controller is developed to guarantee the finite-time stability based on the estimated lumped disturbance information. The stability of the closed-loop system is proved in spite of the aforementioned disturbances via the Lyapunov analysis. Finally, the numerical simulation illustrates the effectiveness of the proposed control strategy.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-28T05:05:18Z
      DOI: 10.1177/09544100221119862
       
  • Ice particle distribution simulation in a transonic axial compressor based
           on Eulerian evaporation coupling model

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      Authors: Anqing Lai, Han Cheng, Meng Li, Jie Pan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      High-altitude ice crystal icing of aero engine is a serious threat to flight safety. Previous studies on ice crystal icing focused on the influence of air flow on ice crystals, but ice crystals also affect the engine flow field, which is often ignored in the research on the influence of ice crystals on engines. Numerical simulation based on Eulerian method is adopted to realize the two-way coupling between the compressor air flow and the particles in this study. The approach is demonstrated using the NASA compressor stage 35. The changes of compressor and particle parameters with different inlet total water content, relative humidity, and median volume diameter are calculated and analyzed, and the influence of ice crystal on the compressor performance is studied. The results show that the variation of relative humidity has a great influence on the particle temperature, median volume diameter, and wet bulb temperature. Median volume diameter has a great influence on the melt ratio. The variation of total water content has little effect on particle temperature, total water content, median volume diameter, and wet bulb temperature. The particle parameters are affected by the flow field of the compressor. The parameters show that the icing is easy to occur at the leading edge of NASA stage 35 stator. By contrast, the overall compressor characteristics, after ice particle injection, the total pressure ratio, and isentropic efficiency of the compressor are increased without considering ice crystal accretion, and the chocking boundary and stall boundary are not affected.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-26T03:01:24Z
      DOI: 10.1177/09544100221113215
       
  • Rotate artificial potential field algorithm toward 3D real-time path
           planning for unmanned aerial vehicle

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      Authors: Zeyan Wu, Shaopeng Dong, Mei Yuan, Jin Cui, Longfei Zhao, Chengbin Tong
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      As one of the key technologies in the development of Unmanned Aerial Vehicle (UAV), the path planning method has an intuitive impact on the real-time performance of UAV. Most existing path planning algorithms have drawbacks in global optimization ability or optimization speed, and cannot meet the requirements of practical applications. To improve the effectiveness and practicability of the path planning algorithm for UAV obstacle avoidance, this paper proposes the Rotate Artificial Potential Field (R-APF) method based on the traditional artificial potential field method. By introducing a new potential field function and stimulating rotating repulsive force, the R-APF solves the problems of local minimum as well as inaccessibility to targets near obstacles, respectively. Convergence of the algorithm is discussed to demonstrate the feasibility of R-APF. This paper also designs and implements algorithm feasibility verification experiments, obstacle shuttle experiments, as well as running time, and efficiency comparison experiments. In addition, the improved Visual-Inertial Navigation System obstacle detection algorithm is introduced to carry out physical verification experiments. Theoretical proof and experimental results show the proposed R-APF method has higher obstacle avoidance capability, shorter running time, and higher success rate compared to other algorithms, and is promising in practical application.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-23T10:56:48Z
      DOI: 10.1177/09544100221113198
       
  • Detumbling motion planning for the space manipulator with grasped targets
           and flexible appendages in the post-capturing phase

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      Authors: Bowen Zhan, Minghe Jin, Boyu Ma, Bincheng Huang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes a detumbling motion planning algorithm for free-flying space manipulator with a grasped tumbling target in the post-capturing phase. This algorithm can not only collision-freely guide the space manipulator and the target to terminal stationary states but also suppress the residual vibration of the flexible appendage on the space manipulator. First, considering the avoidances of self-collisions and motion singularities, a smooth detumbling path is planned for the space manipulator by a proposed smoothing rapid random tree star algorithm (SM-RRT*). Second, a quintic polynomial function is implemented to generate a continuous detumbling trajectory along the detumbling path. Then, with the object of minimizing the residual flexible vibrations and the constrains of joint acceleration limits, an optimization model is established to refine the detumbling trajectory. Finally, the optimization model is solved by an improved particle swarm optimization algorithm (PSO), where a potential field term is included in the generation of the particle velocity to enhance the computational efficiency. Simulation results validate the effectiveness of the proposed detumbling motion planning algorithm.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-22T11:00:00Z
      DOI: 10.1177/09544100221118210
       
  • Sensor fault-tolerant attitude determination system based on the nonlinear
           interacting-multiple-model approach

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      Authors: Banafshe Akbarinia, Hamed Shahmohamadi Ousaloo
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a methodology for satellite sensors' fault detection and diagnosis (FDD) in a fault-tolerant attitude determination system using a nonlinear interacting-multiple-model approach (IMM). Moreover, the fault-tolerant attitude determination system utilizes the IMM approach in the presence of sensors' total fault to estimate faulty sensors and attitude states. This methodology relies on the most conventional satellite attitude sensors including magnetometer, sun sensor, and gyroscope measurements. The presented scheme leads to a significant computational time-saving method due to considering a pre-filter Kalman for fault detection, hence, the proposed FDD approach consists of two stages. In the first stage, the pre-filter Kalman detects any sensor fault and attitude states. In contrast, in the next stage, fault diagnosis and optimal attitude estimation are obtained through the IMM approach. Therefore, the IMM algorithm will be activated to extract the optimal estimation and identify faulty sensor(s). A Monte Carlo type approach is used to verify this technique for various initial conditions. Through numerical and Monte Carlo simulations, it is shown that the proposed scheme is robust against sensors' total fault, and the system is capable of detecting and isolating accurately the faulty sensor. Hardware in the loop tests using satellite dynamics simulator are also used to validate the presented system performance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-17T04:58:53Z
      DOI: 10.1177/09544100221116270
       
  • Model-based microburst identification using a hybridized extended Kalman
           filter with genetic algorithm

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      Authors: E. Mohajeri, Seid H Pourtakdoust, Farshad Pazooki
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Microburst (MB) wind shear is one of the most important meteorological dangers threatening the aircraft (AC) safety and the life of passengers. Though there are some ground-based 3D Lidar systems to detect low-level MB wind shears to alert the pilots, there have been fewer scientific attempts to identify model-based MB parameters via AC onboard air and position data. The latter refers to the development and identification of an acceptable MB model upon which an automatic flight control (AFC) system can be designed to control the AC through wind shear microburst. In essence, accurate knowledge of MB model is an essential prerequisite for design and analysis of AFC systems that can safely fly the AC against microbursts, especially in crucial phases of flight such as takeoff and landing. The present study focuses on online estimation of MB parameters whose results pave the way for effective MB autopilot designs for safe flights through MB. The proposed task is accomplished via a model-based approach using the AC six degrees of freedom (6 DoF) equations of motion (EOM) integrated with the latest verified model of the MB utilizing the extended Kalman filter (EKF). In addition to a sensitivity analysis to determine the key MB model parameters, the performance of the estimation process is enhanced via a hybridization of the genetic algorithm (GA) with the EKF. The results are promising and indicate that the proposed scheme can identify the MB model parameters with sufficient accuracy needed for online applications with AFC design.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-15T05:29:08Z
      DOI: 10.1177/09544100221119864
       
  • Research on the roll control of the flapless aircraft with circulation
           control

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      Authors: Ling-Xiao Li, He-Yong Xu, Yu-Hang Wang, Yue Xu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The purpose of this paper is to study the roll control of the flapless aircraft under low-speed and high-speed flight states and investigate the equivalent control effect (ECE) and the power consumption of the pneumatic control. First, the roll moment coefficient of the aircraft with different aileron deflection angles is calculated. Then the intensity of the jet is adjusted to match the roll moment coefficient, so that the deflection angle of the ailerons and the intensity of the jet corresponding to the same rolling moment are found. Based on the realization of the roll control, the aerodynamic efficiency of the flapless aircraft is evaluated by using the equivalent lift-to-drag ratio (Ecc) considering power consumption. The ECE curves of the pneumatic roll control under low-speed and high-speed flight states are obtained. Under low-speed flight state, the increment of aerodynamic efficiency brought by the jet cannot make up for its power consumption. Under high-speed flight state, the aerodynamic efficiency increment brought by the pneumatic control can compensate its power consumption before Cl = 0.061.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-14T08:11:16Z
      DOI: 10.1177/09544100221119567
       
  • On the underlying dynamics of traffic conflicts related to stochastic
           behaviour

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      Authors: Zsombor Öreg, Hyo-Sang Shin, Antonios Tsourdos
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The aim of this paper is to analyse why and how air traffic conflicts occur as a result of the stochastic behaviour of both the ownship and the intruder and to show how system-level characteristics can be derived from such an analysis. Ensemble dynamics in a given traffic scenario have already been analysed using multi-agent simulations by many; however, such an analysis is hardly ever backed up and interpreted in terms of an analytical study. By making use of directional conflict probability maps, characteristics of integral, system-level quantities can be explained, providing further insight into the relationship of speed distribution parameters and system performance quantities, namely, safety and throughput.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-14T06:50:48Z
      DOI: 10.1177/09544100221117432
       
  • Modeling and research of a multi-stage parachute system for the booster
           recovery

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      Authors: Xiaojun Xing, Lei Feng, Mengping Chen, Yichen Han, Yiming Guo, Xiaoran Chen
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      With the development of the aerospace technology, reducing the cost of exploring space has become the target of most countries. The recovery of rocket boosters is regarded as one of the most effective solutions to this problem. A whole recovery scheme of the drag parachute and controllable parafoil for accurate landing is designed in this paper, in view of the high reliability and low cost of the parachute recovery system. The models of the parachute-payload in the deceleration stage and the parafoil-payload in the gliding stage are established. On the basis of the high-fidelity models, the motion characteristics of the whole recovery process are simulated considering the external disturbances and internal disturbances such as the turbulent wind and angle uncertainty. This work provides the parameter reference for the accurate recovery control of the booster.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-12T08:08:41Z
      DOI: 10.1177/09544100221118238
       
  • Numerical investigation of bending–torsion coupling effect on
           aeroacoustic noise of a flexible unmanned aerial vehicle propeller

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      Authors: Yo-Seb Choi, Suk-Yoon Hong, Jee-Hun Song
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The recent explosion in interest into the use of UAVs for a wide range of commercial applications has also raised awareness of the issue of noise coming from UAVs. This paper introduces a method for predicting the aeroacoustic noise of a flexible UAV propeller while considering bending–torsion coupling. Numerical simulations of a flexible UAV propeller are conducted under hovering conditions to investigate the coupling effect on noise prediction using a fluid–structure interaction and acoustic model based on Formulation 1A of Farassat. The bending–torsion coupling leads to additional bending-induced torsional deformation along with considerable increases in noise and the overall sound pressure level. The results indicate that the noise evaluated without the coupling was underestimated compared to that evaluated with the coupling. Finally, the bending–torsion coupling is shown to be essential for precisely predicting the noise of a rotating flexible UAV propeller to respond to strengthening noise regulations.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-12T05:26:20Z
      DOI: 10.1177/09544100221119040
       
  • Effect of axial slot casing treatment on a counter-rotating axial-flow
           compressor aerodynamic performance and stability

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      Authors: Yanchao Guo, Xiaochen Mao, Lei Wang, Limin Gao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Counter-rotating axial-flow compressor (CRAC) technology is an important technical way to improve the thrust-to-weight ratio of aero-engines. To explore the stall margin improvement potential of axial slot casing treatment (ASCT) in the CRAC, a two-stage CRAC is selected to investigate the influence of axial position and radial deflection angle of slots on the stabilization capability of ASCT by numerical method. The paper also revealed the stability expansion mechanism of ASCT in the CRAC and the effect of casing treatment on the rotor/rotor interference effect between the front and rear rotors. Results show that the axial position of slots has little effect on stall margin improvement capacity of ASCT but has a great influence on peak efficiency. Increasing the radial deflection angle of slots to further improve the stabilization ability of ASCT is not remarkable, but it is beneficial to decline the efficiency penalty. The suppression of tip leakage flow by slots and the transport of low-energy fluid near the blade tip can delay the occurrence of the stall, and the maximum stall margin is improved by about 10.75%. Besides, the ASCT decreases the unsteady interference effect between the rotors and inhibits the potential flow effect of the downstream blade passage and improves the inlet flow field quality of the rear rotors.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-12T03:07:50Z
      DOI: 10.1177/09544100221119030
       
  • Numerical study on rotor tip flow loss in a boundary layer ingesting fan
           under different operating conditions

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      Authors: Hanan Lu, Zhe Yang, Tianyu Pan, Qiushi Li
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      As a key component of boundary layer ingesting (BLI) propulsion system, the BLI fan operates permanently at an inflow distortion condition and the distortion-induced aerodynamic loss in the fan would seriously in turn discount the aerodynamic benefit achievements of BLI propulsion system. Moreover, as the fan rotor rotates along the annulus, the blade tip region will encounter the greatest distortion intensity and operating condition variation, thus contributing to major loss source in the BLI fan rotor. To explore the loss mechanisms in rotor blade tip region of a BLI fan, numerical investigations are conducted to study the influences of BLI inflow distortion on the flow loss in the fan rotor blade tip region at different mass flow working conditions. The results indicate that the flow loss in blade tip region increases notably from near choke to near stall condition, accounting for about 38%–51% of total aerodynamic loss in the BLI fan rotor. The loss in the tip region reaches the maximum at 240° circumferential location where the rotor blade is leaving the distortion region along the annulus because high local blade load and maximum relative Mach number are presented. In the meanwhile, as the rotor blade load increases from near choke to near stall condition, the shock structure in the blade passage varies and the interaction between shock and tip leakage flow is also intensified because of enhanced local leakage flow and forward displacement of shock. At near peak efficiency and near stall conditions, the interaction between the leakage vortex and shock in the tip region is notably intensified at 240° circumferential location and the local leakage vortex expands rapidly after the shock, leading to a vortex breakdown. The resultant flow blockage at 240° circumferential location is much higher than those at other annulus locations and the maximum blockage has increased from 18% to 42% from near choke to near stall condition, contributing fundamentally to the additional loss in the BLI fan. At the same time, by further quantifying local aerodynamic loss, it is also found that the leakage flow loss due to interaction between leakage flow and shock is the major source of loss in the BLI fan rotor, and the vortex breakdown at high blade load condition (from peak efficiency to near stall condition) could even lead to an increment of loss with a slop about three times of that at low blade load condition (near choke condition).
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-06T06:46:56Z
      DOI: 10.1177/09544100221117679
       
  • W-type flying wing radar cross-section analysis

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      Authors: Zeyang Zhou, Jun Huang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To study the electromagnetic scattering characteristics of a W-type flying wing with two rotors, a computing method is presented. The method includes two modules: dynamic grid transformation and instantaneous RCS (radar cross-section) computing. The results show that the surface of the blade and the leading edge of the wing have a high level of scattering under the irradiation of forward radar waves. The scattering characteristics of the rotor support cabin are enhanced when electromagnetic waves are incident from the side. At the given positive elevation angle, the mean of aircraft RCS curve under side direction decreases first and then increases with the increase in azimuth. The fluctuation range of the aircraft RCS curve under different tail azimuths is similar at the given negative elevation angle. The computing method is effective for analyzing the RCS of the W-type flying wing.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-04T02:49:58Z
      DOI: 10.1177/09544100221117319
       
  • Experimental investigation into the aerodynamic and aeroacoustic
           performance of bioinspired small-scale propeller planforms

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      Authors: Foad Moslem, Mehran Masdari, Kirchu Fedir, Behzad Moslem
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The multi-rotors have a limited operational period and generate too much noise, which is insufficient for complex tasks and adversely affects humans’ and animals’ health. Nevertheless, their market has become increasingly popular. Therefore, low-noise products are more competitive, and aerodynamic and acoustic improvements are critical. This investigation aims to design a small bioinspired propeller with the same power input as a conventional propeller to achieve the same or better aerodynamic performance while decreasing noise. Accordingly, an experiment investigated the impacts of operation conditions and varied geometric parameters on six small propellers' aeroacoustic performances with a unique planform shape inspired by five insects and one plant seed, such as Blattodea, Hemiptera, Hymenoptera, Neuroptera, Odonata, and maple seed. Each propeller was operated at eleven rotational speeds ranging from 3000 to 8000 RPM with no freestream velocity for simulating hover conditions. Compared to the baseline propeller, the results demonstrate that all bioinspired propellers produce more thrust for the same power supply, reduce harmonic and broadband noise, and provide a better noise level. Also, their rotational speed is lower and their figure of merit is higher than the baseline propeller at hover flight with 3N thrust. They all outperform the baseline propeller in terms of hover efficiency at all thrust values considered. Besides, the Neuroptera propeller is more efficient than other propellers, decreasing 5.5 W of power and reducing 7.9 dBA at hover flight with 3N thrust and 1.5 meters distance, compared to the baseline propeller.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-02T12:59:59Z
      DOI: 10.1177/09544100221091322
       
  • An unsteady two-dimensional vortex method for the flow separation over a
           flapping wing

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      Authors: Yue Wu, Changchuan Xie, Chao Yang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The flow separation over a very flexible or morphing aircraft, especially during flying or oscillation at a high angle of attack, is stronger than that for conventional aircraft. However, a low-order model for reliably predicting the dynamics of the LEV and its influence on the force is still not found. It is valuable to develop such aerodynamic approaches for optimizing the wing structure and kinematics and for designing a flight control strategy considering the flow separation problem. This paper presents a two-dimensional vortex method in which an artificial boundary is constructed for the velocity adjustment of the vortices near the control panels. This artificial boundary is established in accordance with the thickness of the actual wing. A sub-time step is introduced into the solution process of the vortex method to predict the vortex locations and perform velocity adjustments. Crossing vortices retain only their tangential velocity components relative to the artificial boundary in order to avoid entering the range of the airfoil represented by the artificial boundary. Moreover, the excessive induced velocities on the control panels caused by crossing vortices are decreased, and the nonphysical behaviors and discontinuous pressure are avoided. To demonstrate the advantages of the proposed artificial boundary method in modeling an airfoil during high-angle-of-attack flight, the proposed approach is applied to a flat-plate starting problem and a flapping problem. The simulation results are then compared with the results of several experiments and numerical data for both attached and separated test cases, verifying the capabilities of the proposed method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-08-02T02:51:43Z
      DOI: 10.1177/09544100221100057
       
  • Nonlinear robust fault-tolerant control for turbofan engines with actuator
           faults

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      Authors: Dingding Cheng, Lijun Liu, Zhen Yu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper investigates nonlinear robust fault-tolerant control for turbofan engines with actuator faults. The nonlinear robust fault-tolerant control method is proposed in this paper, which can guarantee the fault tolerance and robustness of turbofan engines when faults and disturbances occur. The design method is implemented in three steps: Firstly, the dynamic effects caused by actuator faults on turbofan engines are analyzed and then the multivariable polynomial state-space model of turbofan engines with actuator faults is proposed. Secondly, appropriate design parameters are chosen according to fault information. Thirdly, the nonlinear robust fault-tolerant control law for turbofan engines with actuator faults is designed by solving an optimization problem. In addition, stability and [math] gain-like for turbofan engines with bounded disturbances and actuator faults are guaranteed by the proposed nonlinear robust fault-tolerant control method. The distinctive characteristic of the paper is that the nonlinear robust fault-tolerant control method for turbofan engines against actuator faults is proposed which can relax the accuracy requirements of the fault diagnosis subsystem and improve the fault-tolerant performance of the closed-loop control system. Simulations show that the nonlinear robust fault-tolerant control method has better control performances including transient responses, disturbance rejection, and fault tolerance for the turbofan engine with actuator faults.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-21T10:33:13Z
      DOI: 10.1177/09544100221097030
       
  • External pressure buckling of composite sandwich conical shells with
           variable skin thickness

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      Authors: Mehdi Zarei, Gholam Hossein Rahimi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, an analytical model is developed to investigate the buckling analysis of the composite sandwich conical shell with variable skin thickness under lateral pressure loading. This problem involves composite shells, which are produced during the filament-winding process, where the skin thickness varies through the length of the shell. An effective smeared method is employed to reduce the reinforced lattice core into a layer. This is done by analyzing forces and moments on a unit cell. Therefore, equivalent stiffness parameters of reinforced lattice core are determined. By superimposing stiffness parameters due to the lattice core with those of the inner and outer skins, the equivalent stiffness of the sandwich panel will be obtained. Governing equations are established based on the first shear deformation theory. The power series method is used to extract the buckling load of the stiffened shell. To verify achieved results, a 3D finite element model is provided. Comparisons showed that the analytical solution is qualified enough to study the buckling behavior of the composite sandwich conical shell. Through this study, the effects of a set of important parameters like stiffener orientation angle, number of stiffeners, semi-vertex angle, and skin lamination are investigated.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-20T10:42:57Z
      DOI: 10.1177/09544100221101764
       
  • Aero-engine on-board model based on big Quick Access Recorder data

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      Authors: Li-Hua Ren, Zhi-Feng Ye, Ye Zhu, Zhan-Yan Xu, Yong-Ping Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      With the development of the Full Authority Digital Engine Controller (FADEC) technology, the aero-engine on-board model is widely used in Engine Health Management (EHM) and control. Due to the FADEC’s limited computational capability and storage capacity, the model should not be very intricate; consequently, the interpolation model is widely utilized. Although the interpolation model’s low precision precludes further development of on-board models for EHM and control. To address the trade-off between precision and complexity, a novel on-board modeling method is proposed based on the Nonlinear Autoregressive with Exogenous Inputs Backpropagation neural network (NARX-BPNN) trained using the mini-batch Levenberg–Marquardt (LM) algorithm on large Quick Access Recorder (QAR) data. The NARX model’s features and time delay are chosen by referring to the line interpolation model, which gives interpretability for feature selection. The combination of a shallow neural network and big data training can guarantee the on-board model’s real-time and storage requirements, as well as its generalizability. The mini-batch LM method can avoid both the local optimum problem in the shallow neural network and the storage difficulty associated with massive data while still achieving a rapid convergence rate due to the LM algorithm’s global view. The NARX-BPNN models are compared to an existing line interpolation model using 100 different aero-engines' QAR data. The results reveal that accuracy may be increased by approximately 30% while maintaining superior dynamic performance and anti-noise capacity compared to the line interpolation approach.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-20T10:11:28Z
      DOI: 10.1177/09544100221110290
       
  • Integral-based robust LPV control of nonlinear flight systems

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      Authors: Reza Tarighi, Amir Hooshang Mazinan, Mohammad Hosein Kazemi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a novel speed control method for an unmanned flight system. A Polytopic Linear Parameter Varying model is generated by linearization of the nonlinear dynamic model around several trim points. As a novelty of this paper, an Integral action over the tracking error is added to a conventional state-feedback to form the proposed control law. Augmenting the proposed control action to the system dynamic, the proposed control law is reassigned as a common state-feedback control problem. An attenuation level for the tracking error under external disturbances is guaranteed by solving the related linear matrix inequalities to compute the control gains. In the end, the designed controller has been implemented for different scenarios in order to maintain the speed in different modes with the ability to control the longitudinal, Lateral, and altitude velocities simultaneously. The simulation results show the effectiveness of the proposed control against the system uncertainties, external disturbances, and the interactions between different channels.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-20T05:55:21Z
      DOI: 10.1177/09544100221109976
       
  • High-order pseudorange rate measurement model for multi-constellation
           LEO/INS integration: Case of Iridium-NEXT, Orbcomm, and Globalstar

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      Authors: Farzan Farhangian, Rene Jr Landry
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An inertial navigation method augmented by Signals of Opportunity (SOPs) of three low earth orbit (LEO) constellations is presented. The downlink signal characteristics of the Iridium-NEXT, Orbcomm, and Globalstar LEO constellations are discussed. Furthermore, a tightly coupled integration model of the inertial navigation system and high-order LEO-SOP Doppler measurement model is designed. We presented a second-order measurement model of the LEO-SOP/INS integration using a second-order extended Kalman filter in which all the unknown states of the receiver and LEO satellites are estimated. The state parameters of the second-order EKF model are the position and velocity of both the receiver and the satellites, as well as the receiver’s orientation, the clock bias, and clock drift of the LEO satellites, and the constant bias of the Inertial Measurement Unit. An experiment is performed using a ground aerial vehicle equipped with a Multi-Constellation Software-Defined Receiver (MC-SDR). The Doppler measurements are provided by observing the downlinks from multiple satellites of the Iridium-NEXT and Orbcomm constellations. As well, the predicted measurement of a Globalstar satellite is used in the designed model. The results show the positioning accuracy of less than 10 m being achieved during a dynamic ground experiment, representing an 82% precision gain as compared against the regular single constellation EKF method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-15T06:45:36Z
      DOI: 10.1177/09544100221113123
       
  • Investigation on a new type of latching mechanism on the satellite-rocket
           docking system and locking dynamic analysis

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      Authors: Qing Lin, Ming Zhang, Jie Ren, Qiuqin Hua
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To meet the in-orbit maintenance requirements of malfunctioning satellites and maintenance satellites rigid connections, a new type of latching mechanism based on satellite-rocket docking ring is proposed, which has light weight, good structural stiffness, simple motion and locking mechanism, simple control logic, high reliability and large range of docking ring size adaptation. A multi-body dynamic model of the docking ring latch mechanism, malfunctioning satellite and maintenance satellite were established, the maximum locking force and maximum friction of the latch mechanism and the maximum stress of the latching joint and crank of the direct force component were analyzed, and the change of locking force and friction under the three typical in-orbit maneuvering conditions were studied. The results show that: the maximum locking force and maximum friction of the latch mechanism on the docking ring is 1300N and 320N, respectively, stable locking force and friction are 300N and 80N, respectively, the maximum stress occurs on connecting rod which is 865 MPa; In-orbit maneuvering has little effect on the locking force and friction of the docking ring latch mechanism, and the docking ring latch mechanism can always lock the malfunctioning satellite steadily and reliably.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-13T09:47:00Z
      DOI: 10.1177/09544100221114686
       
  • Experimental investigation of vortex shedding of an airfoil at post-stall
           incidences

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      Authors: Niosha Fallahpour, Mahmoud Mani, Mohadese Lorestani
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The harmonic vortex shedding from airfoil happens in various incidences. It has noticeable effects on the structure design and aerodynamic performance. In this paper, wind tunnel tests were conducted on a stationary NACA4412 airfoil at angles of attack ranging from [math] to [math] and Re number between [math] and [math] to examine the vortex shedding frequency and Strouhal number. The wake dynamics at post-stall incidences were investigated by surface pressure, wake flow velocity measurement, and smoke flow visualization. Three phases of the wake dynamics were observed with increasing the incidences beyond the stall: (i) the tiny vortices are shed from the airfoil’s suction side with scattered frequencies, (ii) the shear layer is separated from the LE, rolls up over the airfoil’s suction side and forms the harmonic vortex street, and (iii) the separation point moves from the airfoil’s suction side to the pressure side and leads to the vortex shedding like the bluff bodies. Frequency analysis of aerodynamic loads shows that the flow field’s low-frequency feature has a substantial effect normal to the surface while the vortex street unsteadiness impacts both perpendicular and parallel to the surface. The base pressure coefficient increases suddenly by the vortex street onset in the region (ii) and reaches about 0.4. The universal Strouhal number of 0.18 that is independent of Reynolds number was captured for the angles of attack well beyond the stall. Flow visualization shows that the vortex street establishes longitudinally closer to the airfoil at lower freestream velocity compared to the upper one.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-12T06:08:03Z
      DOI: 10.1177/09544100221112718
       
  • Robust design of a fan rotor blade by sweep and lean optimization with
           surface roughness

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      Authors: Man Yu, Lei Shi, Peng Yu, Ka Yao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to reduce the fan rotor aerodynamic performance degradation caused by the increasing of blade surface roughness, optimal design of high bypass ratio fan rotor blade with surface roughness was carried out to improve the aerodynamic performance of the fan rotor in long-term flight operation. With the condition of surface roughness uniformly distributed on the blade, the fan blade was optimized by using sweep and lean technology, and the aerodynamic characteristics of the fan blade with different surface roughness were numerically investigated. Numerical results show that the overall aerodynamic performance of the fan rotor decreases as the equivalent sand roughness ks of the blade increasing from 3 μm to 150 μm. The isentropic efficiency of the original blade decreases by 1.56% when the surface roughness reaches 150 μm. Composite sweep and lean optimization was carried out when ks = 80 μm, the isentropic efficiency of the optimized blade at design point is increased by 0.28%, the second optimization based on the optimized blade above by using the reverse lean technology further improved the fan isentropic efficiency by 0.12%, the degradation caused by surface roughness was reduced by optimization, and the robust design of fan rotor blade was achieved.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-12T03:07:57Z
      DOI: 10.1177/09544100221113118
       
  • A hybrid INDI control for ensuring flying qualities in failures of Xcg
           measurement subsystem

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      Authors: Chongsup Kim
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Modern version of fighter aircraft has a wide range of longitudinal center-of-gravity (Xcg) travel due to wide-range fuel tanks layout, various weapons, many payload stations, and so on. The wide Xcg travel degrades flying qualities of a closed-loop control system; moreover, a catastrophic accident can be caused by loss of stability due to the wide Xcg travel in severe cases. For this reason, the inner-loop control law generally employs additional feedback variables such as weight and Xcg position to guarantee the flying qualities and satisfy stability requirements. Nevertheless, this design approach can seriously deteriorate the flight safety and stability of the aircraft in the event of fuel mismanagement and Xcg measurement subsystem failures. Therefore, additional design technique should be considered to ensure the flight safety in response to the situation of the failure conditions. This paper proposes two types of a hybrid Incremental Nonlinear Dynamic Inversion control to guarantee the minimum flight safety for return to base in case of fuel mismanagement and Xcg measurement subsystem failures. The frequency-domain linear analysis and time-domain simulations were performed based on a supersonic trainer mathematical model to evaluate the performances of the proposed control methods. The evaluation results confirm that the proposed control method satisfies the level of the required flying qualities and ensure flight safety even in the event of the subsystem failures for the Xcg measurement.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-08T06:51:51Z
      DOI: 10.1177/09544100221113429
       
  • Computation of viscous flow characteristics of a supersonic intake using
           eddy-viscosity turbulence models

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      Authors: Subrat Partha Sarathi Pattnaik, NKS Rajan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Results of numerical investigation of flow and performance characteristics of a rectangular supersonic intake experimentally tested at Mach number of 4.03 are presented. The viscous flowfield has been obtained by solving Favre averaged Navier–Stokes equations with two eddy viscosity turbulence models, namely, Mentor’s baseline (BSL) k-ω and shear stress transport (SST) k-ω models. In addition, the effect of wall temperature conditions as well as several configurations of cowl and isolator are simulated to validate the computational methodology. The analysis has been carried out at a freestream Mach number of 4.03 and 0° angle-of-attack, corresponding to a unit Reynolds number of about 6.9×107 m−1. The predicted boundary-layer and the wall static pressure distribution using SST k-ω model shows better agreement with the experimental data compared to the BSL model and hence indicates superior capability to capture the onset and the amount of flow separation due to SWBLIs. Moreover, the terminal shock structure at different operating modes as well as the “unstart because of SWBLIs” is predicted quite accurately using the model. The wall temperature condition is found to have a strong effect on the amount of flow separation at the cowl and the subsequent interactions. Further, the results show that the sidewalls have a marginal effect on the centerline wall static pressure, though a three-dimensional flowfield with two stream-wise vortices are observed close to it as a result of the swept SWBLIs of the cowl shock with the sidewall boundary-layer leading to a higher loss in performance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-06T12:31:59Z
      DOI: 10.1177/09544100221111597
       
  • Effect of the trailing-edge flap on tones due to self-excited oscillation
           within the leading-edge slat cove

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      Authors: Weishuang Lu, Peiqing Liu, Hao Guo
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To study the tonal noise characteristics of the leading-edge slat of high-lift configurations with and without a deployed trailing-edge flap, experiments are conducted in the D5 aero-acoustic wind tunnel at Beihang University. The numerical simulation method is used to obtain the necessary flow information. The experimental results show that low to mid frequency tonal noise generated by self-excited oscillation within the slat cove is dominant and its corresponding frequencies are basically unchanged whether the flap is deployed or not. However, the primary mode of self-excited oscillation within the slat cove switches to a higher one when the flap is deployed. Further analysis results demonstrate that variation of the primary mode is found to be closely related to the flow characteristics in the self-excited oscillation feedback loop. The number of the primary mode is generally proportional to the ratio between the vortex shedding frequency and the self-excited oscillation frequency. The flap being deployed results in an increase in the effective angle of attack of both the main wing and slat, which leads to a thinner separating boundary layer, thus increasing further the vortex shedding frequency and this ratio.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-07-04T02:00:50Z
      DOI: 10.1177/09544100221111305
       
  • Unsteady aerodynamics of plunging cambered foil at low Reynolds number

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      Authors: Masuruddin Shaik, Shyamanta M Hazarika
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The present work focuses on the investigation of unsteady aerodynamics of plunging cambered foil with conditions corresponding to that of a Micro Air Vehicle. The effect of non-dimensional plunge amplitude, plunging frequency and the dimensionless plunge velocity on the propulsive performance of a harmonically plunging cambered foil are studied by varying Reynolds number from 2.5 × 104 to 7.5 × 104. Further, the flow field around the foil is analysed to understand the influence of the above-mentioned parameters and the reasons behind the positive thrust force generation. It is observed that these investigated parameters remarkably influence the instantaneous force coefficients. It is also noticed that these parameters have a significant effect on the topology of the leading edge vortex which can dramatically change the aerodynamic performance of the foil. It is observed that the Reynolds number also has a significant influence on the drag-thrust transition.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-30T06:55:02Z
      DOI: 10.1177/09544100221101724
       
  • Improved scale-resolved predictions of flow and heat transfer past a bluff
           body using partially averaged Navier–Stokes and a high-order eddy
           viscosity closure

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      Authors: Sagar Saroha, Sawan S Sinha
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The partially averaged Navier–Stokes (PANS) methodology has emerged as a viable bridging method of turbulence computations. Partially averaged Navier–Stokes methodology allows the user to implicitly choose the filter cut-off seamlessly in the inertial sub-range of motion. In past, most PANS simulations have been performed using the linear eddy viscosity closure for the unclosed turbulent stresses. Recently, evaluation of the advantages of higher order eddy viscosity closures with the PANS methodology has also been initiated. With our motivation to make further progress in this direction, this study presents an evaluation of PANS methodology wherein the turbulent stresses are modelled involving closures up to the cubic products of the resolved strain-rate and the rotation-rate tensors. After appropriately adapting a popular Reynolds-averaged Navier Stokes cubic closure for the PANS paradigm, an extensive evaluation of the method is performed in the flow past a heated sphere at a Reynolds number of 10,000. Time-averaged PANS predictions of surface-related as well as wake-related quantities are compared against available experimental, direct numerical simulation as well as large eddy simulation results. Indeed, very significant improvements are demonstrated by the PANS methodology in conjunction with the cubic eddy viscosity closure when compared to the corresponding predictions of the PANS methodology using a linear or even a quadratic eddy viscosity closure. This study demonstrates the promising augmentative ability of the higher eddy-viscosity to the PANS framework in performing improved simulations of the separated flows.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-28T08:22:29Z
      DOI: 10.1177/09544100221108609
       
  • A comparative study on class-imbalanced gas turbine fault diagnosis

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      Authors: Mingliang Bai, Jinfu Liu, Zhenhua Long, Jing Luo, Daren Yu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Gas turbines are widely used in various fields, and the failure of gas turbines can cause catastrophic consequences. Health condition monitoring and fault diagnosis of gas turbines can detect faults timely, avoid serious faults, and significantly reduce maintenance costs. Thus, fault diagnosis of gas turbines has great significance. Current researches on gas turbine fault diagnosis mainly focus on the case of abundant fault samples. However, fault data are very rare and the number of normal samples is much larger than the number of fault samples in the industrial scene. This class-imbalance problem widely exists but is hardly focused in the field of gas turbine fault diagnosis. Aiming to solve this problem, this paper introduces the concept of class-imbalanced learning from the machine learning field, summarizes three kinds of class-imbalance addressment methods including oversampling, undersampling, and sample weighting, and proposes a new combination method of focal loss and random oversampling for addressing class-imbalance in deep neural networks, and performs a systematic comparative study on class-imbalanced gas turbine fault diagnosis. Experimental results show that class-imbalance can seriously reduce the fault diagnosis accuracy. Through these class-imbalance addressment methods, diagnosis accuracy is greatly improved. Comparative experiments also show that the proposed combination method can obtain the best diagnosis accuracy among all the compared methods in class-imbalanced situation. Through this comparative study, a detailed guideline for improving diagnosis accuracy under class-imbalanced circumstance is provided.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-28T03:57:24Z
      DOI: 10.1177/09544100221107252
       
  • Pressure oscillation suppression and mode transition for supersonic cavity
           flows controlled by upstream mass injections

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      Authors: Chao Zhang, Zhaojun Xi, Renfu Li, Ningliang Kong
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Direct numerical simulations were performed to investigate an active control strategy for supersonic (Mach 1.8 and 2.2) flows past a rectangle cavity with a length-to-depth ratio of 4. A steady mass injection is applied upstream of the cavity as the active control technique. The pressure oscillations are significantly suppressed by two mechanisms: (1) thickening and lifting of the cavity shear layer to alleviate downstream impingement with the cavity trailing edge and (2) weakening of the cavity shear layer instability. When the initial boundary layer thickness of the supersonic cavity flow is relatively small, a stronger mass injection leads to increased cavity shear layer thickening and uplift, increased weakening of the shear layer instability, and higher suppression of the pressure oscillations. When the Mach number equals 1.8, the dominant flow mode changes from the Rossiter II mode to the Rossiter III mode under active control, which is detected by the dynamic mode decomposition. However, the mode transition under active control substantially differs if the initial boundary layer thickness is relatively large, for which the pressure oscillation suppression controlled by the high-velocity upstream mass injection is not better than a low-velocity injection, owing to a higher shear layer instability. Mechanism (2) listed above is therefore more important than mechanism (1).
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-27T09:25:54Z
      DOI: 10.1177/09544100221110655
       
  • Numerical solution for elliptical orbit pursuit-evasion game via deep
           neural networks and pseudospectral method

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      Authors: Cheng-ming Zhang, Yan-wei Zhu, Le-ping Yang, Xin Zeng, Run-de Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents an efficient and stable DNNs-based Radau pseudospectral method for the free-time elliptical orbit pursuit-evasion game based on the equivalent reconstruction of the game model. Firstly, the relative dynamics equations are established by adding the nonlinear terms caused by the eccentricity to the Hill–Clohessy–Wilshire equations. Then the original pursuit-evasion problem is deduced to a 4-dimensional one-sided optimal control problem (OCP) based on the equivalent reconstruction. Secondly, in order to apply the deep neural networks (DNNs) to map the relationship between the OCP and the solution, the normalization of costates is introduced to eliminate the non-uniqueness of solutions when generating samples for training DNNs. Thirdly, the DNNs-based Radau pseudospectral method is proposed where the DNNs output the guesses of solutions to the derived OCP and the Radau pseudospectral method optimizes the histories of controls obtained by the guesses to the convergence. The simulation results demonstrate that the proposed method converges more stably and decreases the calculation time greatly compared with the traditional indirect method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-23T02:34:38Z
      DOI: 10.1177/09544100221109980
       
  • A unified in-time correction-based testability growth model and its
           application on test planning

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      Authors: Xiaohua Li, Chenxu Zhao, Bo Lu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Test management is a critical problem for in-time correction-based testability growth test. For the existing testability growth model, they are either too complex to be implemented in practice, or do not have the ability to draw a smooth test planning/projecting curve. This paper proposes a unified model for in-time correction-based testability growth test and presents its application on the test planning. Firstly, a simple model with only three parameters is developed, and its compatibility with the original Markov model is proved. The revised model only has three parameters, which can reduce the complexity of parameters estimation and increase the certainty of the test planning. Secondly, the paper incorporates the simplified transition probability model with the test cost model and studies the optimal test planning method with the minimum test cost criterion. To illustrate the efficacy of the proposed model, an application of the model to an attitude control system of a helicopter available in the open literature is given. The simulation demonstrates that the model and the method proposed in this paper are reasonable, and they are useful for effectively managing the testability growth test planning problem during system maturation.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-22T09:51:48Z
      DOI: 10.1177/09544100221108612
       
  • Comparison of the Newton–Raphson Method and genetic algorithm solutions
           for nonlinear aircraft trim analysis

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      Authors: Ugur Ozdemir
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      As the number of unknowns in trim analysis increases, the problem becomes more complicated, and traditional methods begin to fail. Common problems with conventional methods may be an ill-conditioned matrix, rounding errors, and division by zero. Furthermore, these methods are likely to find the local optimum, not the global optimum. In such cases, hybrid use with intelligent methods such as genetic algorithms is recommended. In this study, a flight situation that the Newton–Raphson method has for difficulty in solving is selected for a six-degree-of-freedom nonlinear trim analysis. Trim analysis was performed using the Newton–Raphson method, genetic algorithm, and by their hybrid use, respectively. The Newton–Raphson method had convergence problems despite very good initial guesses. The genetic algorithm was able to solve the same problem by itself. The unknowns in trim analysis, such as deflection angles of an elevator, a rudder, and an aileron, have physical limits, whereas the constraints make conventional methods more complicated, and the ability to use these limits in the genetic algorithm narrows the solution space and reduces the computation time. The hybrid use of the GA and Newton–Raphson method significantly increased the performance of the Newton–Raphson method and eliminated the convergence problem. It has been shown that a 6-degree-of-freedom trim problem, which traditional numerical methods such as the Newton–Raphson method have for difficulty in solving, can be solved easily and effectively with the hybrid use of the GA and the Newton–Raphson method. The strength of the proposed hybrid method to solve a highly nonlinear trim problem was demonstrated.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-20T03:51:26Z
      DOI: 10.1177/09544100221107726
       
  • Numerical study on detonation initiation process in the chamber with
           characteristic structures of the dual-mode scramjet combustor

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      Authors: Lisi Wei, Zhiwu Wang, Weifeng Qin, Longfei Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to improve the performance of traditional ramjet, a ramjet based on pulse detonation (PD-Ramjet) instead of isobaric combustion was proposed. Several special-shaped detonation chambers which retained the characteristic structures of the dual-mode scramjet combustor were designed. Characteristic structures included the expansion channel and the cavity. The filling process and detonation initiation process of the stoichiometric hydrogen/air mixture under the incoming flow condition of the sub-combustion mode were studied in the detonation chambers with characteristic structures by two-dimensional numerical simulation method, and the influences of the characteristic structures on the filling process and detonation initiation process were analyzed. The simulation and analysis results indicated that the hydrogen concentration at both sides of the chamber near the outlet was low due to the structure of the expansion channel, and the pressure and velocity of the detonation wave decreased gradually after the expansion channel. The cavity had a significant influence on the filling process, which resulted in the uneven hydrogen concentration downstream the cavity, especially near the outlet of the chamber. The intensity of the detonation wave attenuated to a certain extent by reason of the cavity, where the peak pressure first decayed due to the sudden expansion of the flow path and then rose owing to the reflection at the cavity aft wall.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-15T02:46:50Z
      DOI: 10.1177/09544100221107508
       
  • Turbine inlet temperature effects on the start process of an expansion
           cycle liquid propellant rocket engine

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      Authors: Mohammad Amin Eskandari, Hassan Karimi, Ali Sarvari, Mahyar Naderi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The main objective of this study is to investigate the effect of turbine inlet temperature on the transient phase of expansion cycle liquid propellant rocket engines during start. For this purpose, the non-linear differential mathematical model for 15 main components of the engine is derived, and the corresponding interaction between them is established. Afterward, the model is simulated using MATLAB Simulink, and 150 equations are solved with the Newton–Raphson method. The RL10 expansion cycle liquid propellant rocket engine is selected as a case study, and its dynamic behavior is simulated, and the results are compared with the experimental data. The simulation results showed that the present model for engine dynamic parameters, including thrust-chamber pressure, fuel, oxidizer mass flow rate, and turbo-pump speed, has less than 5% error compared to previous literatures. Using the prepared modeling software, the effect of turbine inlet temperature is studied on the engine start process. The obtained results demonstrated that inappropriate temperature profile during start transient might cause an engine malfunction while entering the nominal working regime.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-15T01:02:34Z
      DOI: 10.1177/09544100221090797
       
  • Effect of hexagonal stringer design on bulging factor and stress intensity
           factor of cracks in the skin of pressurized aircraft fuselage

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      Authors: Ahmed F Zayati, Tarek Lazghab, Mohamed Soula
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Aircraft structural fatigue is a serious issue. Untreated, it could lead to failure. Several aircraft accidents were caused by widespread fatigue damage. For cracks in the fuselage, the stress state is due to the bulging around the crack caused by applied internal pressure. This condition is characterized by a parameter called the bulging factor; it compares the stress intensity factor of a crack in curved shell to its counterpart in a plate. Bulging factor expressions are available for longitudinal and circumferential cracks but less for slanted cracks.The underlying structure that stiffens the skin of the fuselage has a direct impact on the stress intensity factor and the bulging factor of the crack. A hexagonal grid stiffening pattern has been shown to provide sufficient stiffening to the fuselage skin while using a lesser amount of material compared to the traditional orthogonal grid design. However, the response of this grid pattern in the presence of a cracked fuselage has not been studied.The current paper aims to estimate the effect of the hexagonal grid pattern on the bulging factor and stress intensity factor of cracks of various lengths and orientations in the skin of the fuselage. Results obtained are compared to the conventional orthogonal grid stiffening pattern of a fuselage structure. Several patterns were considered.Resultsshow that cracks of different lengths and orientations in hexagonal grid stiffened panels had stress intensity factors and bulging factors that are comparable to the base case within a margin of 2%–8%.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T11:37:37Z
      DOI: 10.1177/09544100221107724
       
  • Strain energy form coefficients for bending of short beams having full and
           

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      Authors: Toufik Yahiaoui, Toufik Zebbiche
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The aim of this work is to develop a new generalized formula and a numerical computation program for evaluating the energy form coefficient of a complex and arbitrary cross section for full and thin-walled cross section with respect to any central axis, for the bending of beams of small lengths in comparison with the transverse dimension of the section. This coefficient plays a very important role in the calculation of the deformation energy of beams subjected to bending under the effect of a shearing force for short beams. It also enters in the formulation of FEM bending model, in order to calculate the stresses and the strains due to the external forces. The application is made for complex sections used in various fields of construction and in particular for airfoils designed for aerospace construction. A method is developed to calculate this coefficient as a function of the rotation of the central axes. The calculation of the area, the moments, and the product of inertias with respect to the central axes is necessary. The formula for calculating this coefficient is presented as a definite integral of a non-analytical function determined point by point along the direction of the application of the shear force. This function is based on the calculation of the partial static moments. The calculation of the latter is based on the development of a technique by subdividing the upper part of the section into adjacent common triangles at one point for the full solid section or by segments on the boundary for the thin-walled section. To speed up the process of numerically calculating this integral with high precision and reduced time, Gauss Legendre quadrature of order 40 is used. The calculation of the distribution of the tangential stress as well as its maximum value is determined. A shear shape coefficient is therefore determined. In the second part of this work, an application is made for the static calculation by the FEM of a hyper static beam with a view to determining the influence of this coefficient on all the parameters of resistance and bending stiffness as a correction of the classical model of bending by the FEM. A study of the error made by the classical bending model on our shear effect model is presented. A coefficient of efficiency of a section is presented.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T11:01:24Z
      DOI: 10.1177/09544100221107247
       
  • A modified unsteady-nonlinear aeroelastic model for flapping wings

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      Authors: Seid H Pourtakdoust, Hadi Zare, Arian Bighashdel
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A novel integrated aeroelastic model of flapping wings (FWs) undergoing a prescribed rigid body motion is presented. In this respect, the FW nonlinear structural dynamics is enhanced via a newly proposed modification of implicit condensation and expansion (MICE) method that better considers the structural nonlinear effects. In addition, the unsteady aerodynamic model is also an extension of the widely utilized modified strip theory (MST) in which the flexibility effects are accounted for (MST-Flex). The integrated utility of the proposed generalized MICE and MST-Flex is demonstrated to be more realistic for elastic FW flight simulation applications. The prescribed rigid body motion is produced via a servo motor whose dynamics is also considered for the analysis. A special case study is also performed whose combined aeroelastic solution is determined and validated under a sinusoidal flapping motion. To this end, an experimental setup is designed and tested in order to validate the proposed integrated approach for aeroelastic modeling of FWs. There is very good agreement between the numerical and experimental results for elastic FW aerodynamics. It should be noted that the proposed integrated aeroelastic approach is readily adaptable to all kinds of elastic wings with arbitrary geometry and various combination of structural elements.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T05:03:01Z
      DOI: 10.1177/09544100221108316
       
  • Optimal flight trajectory synthesis for an anti-collision maneouvre
           performed within environment of moving obstacles

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      Authors: Jerzy Graffstein
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      For solving the airplane-to-obstacle collision avoidance problem, two methods are necessary, that is, one for detecting a collision threat and the other one for synthesizing a safe manoeuvre avoiding threating obstacles. In the article, a method for detecting a threat of collision to obstacle was presented for the case of many obstacles moving within the neighbourhood of the airplane. Methods for optimal anti-collision trajectory synthesis and for proving the workability of such a result were proposed too. A solution of an optimisation problem, obtained by the swarm of particles optimization (PSO) was used for trajectory synthesis. A form of quality index was proposed for this task and the analyses of its behaviour for several values of weighting factors were presented. Results of simulations of flight along an optimal, anti-collision manoeuvre trajectory proved that such a manoeuvre is workable.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T02:25:48Z
      DOI: 10.1177/09544100221107725
       
  • Helicopter flight dynamics with simulated rainfall

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      Authors: Guozhi Li, Yihua Cao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Sustaining flight operation that encounters with rainfall might be a challenge to a pilot due to lacking of understanding flight dynamics in the rain conditions. This paper, combined with a computational fluid dynamics (CFD) technique, develops a nonlinear flight dynamics model in the rain conditions that can be capable of exploring UH-60A single-rotor helicopter flight dynamics in the rain conditions, including trim, stability, and controllability. Firstly, in order to obtain a data-driven basis relating to multiple working conditions of the blades, a CFD-based method of simulation of the blade airfoil in the conditions of the angles of attack ranging from −26° to 26° and under a thunderstorm heavy rain scenario when the rate of rainfall is 1500 mm/h is developed. Then, these data are incorporated into a nonlinear flight dynamics model in the form of coefficient increments. Numerical simulations are conducted in the range of the flight velocities from 0 knots to 160 knots. The quantitative results indicate that rainfall degrades the blade airfoil aerodynamic performance and increases the rotor torque and required power, affecting the helicopter trim, stability, and controllability. More importantly, helicopter that flies in a small or moderate flight velocity and that encounters rainfall might be a relative serious case, which should be paid attention to.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T02:14:27Z
      DOI: 10.1177/09544100221107255
       
  • Investigation on flame characteristics approaching thermal chocking in a
           cavity-based supersonic combustor

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      Authors: Zun Cai, Jianbin Li, Taiyu Wang, Yanan Wang, Jiajian Zhu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This study experimentally investigated the combustion process in a cavity-based supersonic combustor at the inflow condition of Mach 2.92 with stagnation pressure 2.6 MPa and stagnation temperature 1530 K. Time-averaged flame distribution and oscillation characteristics were revealed by post-processing CH* chemiluminescence images. Wall pressures along the combustor bottom wall were also measured to provide quantitative information. Representative cascaded injection set-ups upstreaming the cavity were selected to compare ethylene flame characteristics. It is found that the combustion process is approaching thermal chocking when increasing the equivalence ratio to 0.8 according to the one-dimensional analysis of the Mach number distribution. At the same equivalence ratio, increasing the number of the cascaded injectors by lowering the injection pressure is not beneficial for the combustion enhancement, indicating that the injection pressure is also a key factor affecting the combustion heat release. However, increasing the injection pressure can cause obvious flame oscillations above the cavity as well as increasing the axis distance of the injectors. As a result, the injection scheme with two cascaded injectors which have the injection distance of 0.1 and 0.4 time the length of the cavity floor, respectively, upstreaming the cavity is suggested as a favorable scheme for scramjet applications.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-14T01:32:22Z
      DOI: 10.1177/09544100221107248
       
  • Extended aeroacoustic spanwise correction method for the aerodynamic noise
           prediction of large-span objects

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      Authors: Weijie Chen, Kangshen Xiang, Liangfeng Wang, Fan Tong, Weiyang Qiao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In a numerical study, a shorter span extent than experiment is often used to save the computational resource. The predicted sound pressure level should be corrected before compared with the experimental results. This study concerns the extended aeroacoustic spanwise correction method for the noise prediction radiated from large-span objects. Four new types of spanwise correction models are derived based on the assumption of the spanwise coherence function taking the form of a rectangular function, a trigonometric function, a Laplacian function and a Gaussian function, respectively. The large eddy simulation (LES) combined with the acoustic analogy theory is used for the aerodynamic noise prediction. The predicted far-field sound levels are then corrected by the proposed spanwise correction methods for the large-span objects. Far-field acoustic measurements and near-field hot-wire measurements are also performed in an anechoic wind tunnel for validation purpose. The predicted aerodynamic and aeroacoustic results are found in good agreement with the experiments with the proposed spanwise correction method. The present models based on the Laplacian function and Gaussian function are unified models taking the advantage of that there is no need to compare the relative extent of the numerical length, experimental length, and coherence length. The results also indicate that although there is no significant difference between the various functions, corrections based on the Gaussian profile seem to perform better compared with other functions.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-12T11:53:29Z
      DOI: 10.1177/09544100221107251
       
  • A hybrid trim strategy for coaxial compound helicopter

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      Authors: Yuan Su, Zeyuan Wang, Yihua Cao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Interest in the coaxial compound helicopter (CCH) has been increasing in the civil aviation and engineering community for its high-speed and high-maneuverability features, and is likely to continue to do so for the foreseeable future. Since the control in CCH is totally different from the conventional helicopter, the redundant control strategy design is one of the biggest challenges. In this study, the CCH model based on XH-59A is built to investigate the impact of the propeller and the elevator on the flight performance. Four trim strategies with different objectives are proposed and then compared to find the optimal control allocation. A heuristic descent search method is applied to search the optimal velocity at which the propeller and the elevator are engaged. A significant improvement of power required at medium- and high-speed with acceptable rotor airloads increment was found by using the Hybrid Trim strategy in the speed range of 0–100 m/s, with regard to a pre-configured pitch angle schedule. The corresponding control variables obtained located in a reasonable control range, with a maximum power reduced of 13% at 100 m/s, which showcase the potential of the Hybrid Trim strategy.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-12T08:20:46Z
      DOI: 10.1177/09544100221103021
       
  • Feature extraction of rotor-stator rubbing faults based on harmonic fusion
           vector bispectrum, ITD and Hjorth parameters

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      Authors: Mingyue Yu, Haonan Cong, Wangying Chen, Minghe Fang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To solve the difficulty in extracting the characteristics of rotor–stator rubbing faults, the paper has proposed the combined method of Complexity parameter, the harmonic fusion vector bispectrum (HFVB), and intrinsic time-scale decomposition (ITD). First, to fully embody the characteristic information of fault, the HFVB is used to blend the information of signals collected from sensors installed in different positions. Second, taking in mind that the ITD algorithm can embody the effective separation of nonstationary and nonlinear signals, the ITD algorithm makes the separation of blended signals. Third, regarding the important influence of signal complexity on fault characteristic extraction, the complexity parameter of Hjorth parameters can provide very great embodiment of signal complexity. Complexity parameter of Hjorth parameters is introduced as a characteristic parameter index to make a option of proper rotation component (PRC) which can show the characteristics of rubbing fault better. Fourth, signals are reconstructed based on chosen signal components. Meanwhile, to reduce the influence of noise, reconstructed signals are denoised accordingly. Finally, implement the characteristic extraction and fault identification of rubbing faults according to the square demodulation spectrum (SDF) of denoised signals. The result indicates that the harmonic fusion vector bispectrum method can embody the effective blending of fault information; the complexity parameter in Hjorth parameter can serve as the index parameter for option of sensitive characteristic components of rubbing faults. Based on the proposed method, in the square demodulation spectrum of reconstructed signals, it can effectively and precisely provide the characteristics of rotor–stator rubbing fault and successfully identify a fault type.8714542030
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-11T05:38:16Z
      DOI: 10.1177/09544100221107256
       
  • Multi-objective nozzle design optimization for maximum thrust vectoring
           performance

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      Authors: Saadia Afridi, Tariq Amin Khan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Thrust vectoring is a promising technology that offers the potential for improved maneuverability, control efficiency, and stealth characteristics of aircraft. Optimized nozzle design over a range of operating conditions is one of the most crucial factors for maximum thrust vectoring operation. Our goal was to investigate the optimal design of bypass dual throat nozzle to maximize thrust vectoring. We performed a multi-objective optimization study by varying the nozzle bypass angle, convergence angle, and bypass width to see what impact these parameters had on the performance of the bypass dual throat nozzle. A steady numerical simulation has been performed on 55 different nozzle configurations to compare their thrust vectoring performance and losses. In all simulations, the k-ϵ turbulence model is used to determine the vectoring states of the nozzle. The computational fluid dynamics analysis was followed by a multi-objective optimization process using the Response Surface Methodology within the ModeFrontier software. The testing of the optimized nozzle shapes using ANSYS FLUENT verified the accuracy and reliability of the multi-objective optimization algorithm. These findings suggest that nozzle convergence does not significantly affect thrust vectoring. In contrast, bypass width and bypass angle significantly affected thrust vectoring.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-09T10:42:37Z
      DOI: 10.1177/09544100221106656
       
  • Three-dimensional continuous-time integrated guidance and control design
           using model predictive control

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      Authors: Reza Sheikhbahaei, Saeed Khankalantary
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this study, a novel three-dimensional continuous-time integrated guidance and control (IGC) scheme is presented. The proposed method is developed on the basis of generalized model predictive control (GMPC) approach and super-twisting extended state observer (STESO). The GMPC is used to generate the optimal closed form control law for the interceptor and the STESO is applied to estimate the maneuvering target lateral accelerations as well as the lumped disturbances. To the aim of IGC design, a six-degrees-of-freedom model based on the interceptor-target kinematics and interceptor dynamics is constructed. Afterward, the GMPC control law formulation for a nonlinear system exposed to disturbances is extracted. Finally, the effectiveness of the proposed IGC system is studied by numerical simulations. The simulation results reveal satisfactory interception performance including less energy consumption in comparison to a recently proposed successful IGC method.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-07T06:23:59Z
      DOI: 10.1177/09544100221103320
       
  • Adaptive neural tracking control of constrained waverider vehicles via
           single-network adaptive dynamic programming

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      Authors: Qiang Qi, Xiangwei Bu, Baoxu Jiang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The approximate optimization is considered though adaptive dynamic programming (ADP) method for waverider vehicles (WVs). This method can achieve the stability, robustness, and near optimization of the tracking problem for WVs. First, baseline controllers are designed for both velocity subsystem and altitude subsystem via neural network approximation. Meantime, novel auxiliary systems are implemented to compensate the desired control law with actuator saturation. Then, transient optimal controllers are developed using single-network adaptive critic method. Moreover, the stability of closed-loop systems, and the convergence of both the tracking error and the auxiliary system are theoretically proved. Finally, the superiority of the proposed method is proved via compared simulation results.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-06T06:30:34Z
      DOI: 10.1177/09544100221097531
       
  • Aerodynamic performance characterization of bio-inspired wings with
           leading edge tubercles at low Reynolds number

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      Authors: V T Gopinathan, J Bruce Ralphin Rose
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      On the observation of biomimetic Humpback Whale (HW) flippers, the airfoil aerodynamic performance characteristics are explored. The Leading Edge (LE) tubercle geometry was inspired by the flipper of HW that has rounded LE protuberances and tapered trailing edge configurations. The tubercles have excellent flow control characteristics at the post-stall region. Aerodynamic characteristics of airfoils such as NACA0015 and NACA4415 with LE tubercles are experimentally and numerically investigated at the low Reynolds number about Re = 1.83 × 105. The bio-inspired modified airfoils (HUMP 0015 and 4415) are designed with the amplitude to wavelength ratio [math] of 0.05. The numerical simulation over the modified airfoils shows that, at higher Angle of Attack the flow separation is delayed in the peak region whereas the early flow separation is observed in the trough region adjacent to the LE. The boundary layer flow separation analysis is done extensively through numerical simulations and the velocity vector profiles are captured at different chordwise positions. The stall delay phenomenon is observed through the outcome of this research that specifically insists at the peak region of tubercles. Computation of Coefficient of pressure [math] distribution is also done by both numerical and wind tunnel experiments. Analysis of [math] distribution allows the identification of critical regions that initiate the adverse pressure gradient and region of flow separation. It is a novel effort to predict the Coefficients of Lift [math] and Drag [math] concerning the bio-inspired airfoils through [math] distribution such that the influence of flow separation and vortex distribution are characterized for the modified and baseline airfoils. Comparison of [math], [math], and [math] between the baseline and modified airfoils reveal the enhanced momentum transfer characteristics of bio-inspired tubercles.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-04T04:12:35Z
      DOI: 10.1177/09544100221103737
       
  • Integrated control scheme for a large membrane diffractive space telescope

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      Authors: Liang Tang, Zixi Guo, Xiao Feng, Xin Guan, Kebei Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      For higher resolution, next-generation space telescopes would be equipped with 10–20 m scale membrane diffractive primary lenses, and would have 100 m scale focal length. The large and flexible structure makes high-accuracy and high-stability control a great challenge. Specifically, both high-frequency and low-frequency disturbances must be attenuated, and the relative motion between the primary lens and the receiver (composed of the correcting optics and the imaging sensor) must be controlled. This paper presents a novel integrated control scheme to achieve the strict control goals. The dynamic model of a membrane diffractive space telescope is presented, where both high-frequency and low-frequency disturbances are considered. Nonlinear deformation of the flexible structure is also taken into account. The integrated control scheme consists of 3 parts: (1) an Agile Stable Precision platform (ASP), which can not only reduce the high-frequency vibrations for the receiver but also act as the actuator in the receiver control system; (2) a neural network controller for the spacecraft bus, which control the attitude of the spacecraft bus under uncertain low-frequency disturbances; (3) a finite-time neural network controller for the receiver to make the relative position and attitude of the receiver track on the expected state as fast as possible. Numerical simulations were carried out to verify the superiority of the integrated control scheme. Compared with traditional single stage spacecraft control (i.e., without the ASP), the accuracy and stability of the relative position and attitude are improved by at least one order of magnitude, and the settling time is greatly reduced.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-28T10:06:12Z
      DOI: 10.1177/09544100221100049
       
  • High-speed rarefied gas flow simulations using Quasi-Gas Dynamic equations
           with slip and jump boundary conditions

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      Authors: Nam TP Le, Phuc T Huynh
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The high-speed rarefied gas flow simulation is essential for the aerothermodynamic design of high-altitude vehicles. Recently, the Quasi-Gas Dynamic (QGD) equations have been implemented in OpenFOAM as a CFD solver named QGDFoam. In computational fluid dynamics (CFD), the accuracy of the prediction of the surface quantities depends on the slip and jump boundary conditions applied to the surfaces. In the present work, various first-order and second-order slip and jump boundary conditions have been numerically implemented into the solver QGDFoam in OpenFOAM to obtain a completed solver for simulating the rarefied gas flows. It then captures the surface quantities of the gas flows, such as the surface gas pressure, the slip velocity, and surface gas temperature. This completed solver is validated for the sharp-leading-edge wedge, the compression ramp, and the NACA 0012 micro-airfoil cases. Using the QGD model with the slip and jump conditions extends its application and enhances it to simulate high-speed rarefied gas flows. The simulation results show that the slip and jump conditions have been successfully employed with the QGD equations and give good results for predicting the surface quantities compared with the DSMC data.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-28T04:44:03Z
      DOI: 10.1177/09544100221103752
       
  • Toward the feasible solution of a long-lasting dynamic similitude problem

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      Authors: Pedram Hajipourzadeh, Afshin Banazadeh
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Dynamic similar models are designed to study the flight behavior of the full-scale aircraft in early design stages. Due to physical and operational constraints, full dynamic similarity between the scaled-down model and full-scale aircraft is not feasible. Thus, the scale model would be flying at different Reynolds number and Mach number. A given aircraft configuration with specific aerodynamic characteristics will have different performance if Mach number and Reynolds number are changed considerably, which results in different dynamic behavior of the scale model. To compensate for these dissimilarities, it is proposed to modify the airfoil geometry of the scale model to preserve aerodynamic similarity. In this study, based on the flight regime and design requirements, maximum thickness of the airfoil, maximum camber, and their respective location are modified to preserve aerodynamic characteristics at different Mach and Reynolds numbers. Geometry optimization was performed using Particle Swarm Optimization and the geometry optimization results show that it is possible to mitigate the change in Reynolds and Mach number in various flight conditions. It has been shown that optimized geometries of all test cases had airfoils with lower maximum thickness and slightly higher maximum camber.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-27T07:30:20Z
      DOI: 10.1177/09544100221103007
       
  • Unsteady aerodynamic analysis and effectiveness of bio-inspired flapping
           wings in V-formation flight

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      Authors: Ethan Billingsley, Mehdi Ghommem, Rui Vasconcellos, Abdessattar Abdelkefi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Several bird species have been observed to fly in V-formation, an arrangement which exploits aerodynamic features to allow the group to conserve energy when migrating over long distances without stopping and feeding. The use of such grouping arrangement and organized pattern has demonstrated longer endurance and less power consumption in comparison with single flights. In this work, a computationally efficient potential flow solver based on the unsteady vortex lattice method (UVLM) is employed to assess the aerodynamic performance of flapping wings in forward flight in terms of lift and thrust generation along with the propulsive efficiency. The UVLM has the capability to simulate incompressible and inviscid flows over moving thin wings where the separation lines are known a priori. A bio-inspired, albatross wing shape is considered and its aerodynamic performance in formation flights is compared against conventional elliptical and rectangular wing shapes. The aerodynamic analysis is carried out for different wing arrangements of 3-body and 5-body V-formations to determine the optimal spacing parameters leading to maximum propulsive efficiency. The simulation results reveal that, at the optimal formation angle and separation distance, the albatross-inspired wing shape produces the most lift over the flapping cycle, while the rectangular wing shape generates the most thrust over the flapping cycle. Furthermore, the optimal configuration in terms of propulsive efficiency is found to be a 5-body V-formation utilizing the albatross wing shape with a separation distance set to one-third of the span and a formation angle set to 139°. The present study provides guidance for the design of multi-flapping wing air vehicles based on the expected flight mission. The albatross wing shape is found to have superior capability in producing lift, while the elliptical wing shape is observed to consume less power. The rectangular wing shape is found to produce higher thrust and then can achieve faster forward motion.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-27T07:10:05Z
      DOI: 10.1177/09544100221103020
       
  • Performance evaluation of a novel adaptive variable structure state
           estimator

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      Authors: Nilanjan Patra, Smita Sadhu, Tapan Kumar Ghoshal
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An improved nonlinear adaptive state estimator called Adaptive Smooth Variable Structure Filter ASVSF has been proposed and its algorithm described. ASVSF extends the functionality and performance of a previously reported robust smooth variable structure filter (SVSF) with optimal boundary layer (SVSF-OBL). Improvement in performance includes the provision for accommodating unknown and time varying process noise covariance, which generally characterizes modelling uncertainty. The novelty of this proposed ASVSF estimator, which inherits the features of the SVSF, is that it adaptively provides an estimate of the unknown time varying process noise covariance (and hence called adaptive SVSF or ASVSF) which is required for determining the optimal boundary layer width of SVSF-OBL thus obviating the need of the prior knowledge of the process noise covariance. This makes the proposed estimator performance to be insensitive to (and therefore robust with respect to) unknown time varying process noise covariance while retaining the optimality of SVSF-OBL. The performance of the proposed ASVSF estimator is evaluated using Monte Carlo simulation and is compared with previously reported state estimators using a case of maneuvering civilian aircraft where a simplified and grossly approximate process model is used in the estimator/filter for tracking and thereby generating a time varying and unknown process noise covariance situation. Three different measures of Root Mean Square (RMS) error over the trajectory have been used for comparison which demonstrates the strengths of the proposed ASVSF estimator.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-26T07:53:04Z
      DOI: 10.1177/09544100221103328
       
  • Effects of asymmetric stroke deviation on the aerodynamic performance of
           flapping wing

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      Authors: Fujia Hu, Yuanying Wang, Dian Li, Xiaomin Liu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The kinematics of insect flapping flight are complex and asymmetric, which are contributed to their superior flying capabilities, and the design of novel flapping micro air vehicles can draw inspiration from relevant researches. Previous studies usually focus on the wing with asymmetric stroke or pitch motions. A trajectory with asymmetric deviation motion, named as “pear-shaped” pattern, is proposed in current work. The hovering aerodynamics and vortex dynamics of a rigid flapping wing have been numerically investigated by comparing with that of “line-shaped” pattern with no deviation. In order to have a better insight into the influences of the asymmetric deviation, we change the kinematic parameters, that is, stroke amplitude, pitching amplitude, deviation amplitude, and phase lag between stroke and pitch angles. The results show that the wing with asymmetric deviation exhibits superior capability in lift enhancement for most of the cases analyzed, which is accompanied by the extra power cost and slight reduction in efficiency. The asymmetric deviation in cases with high stroke amplitude or low pitching amplitude may be considered as a cost-saving strategy, subject to slight damage on lift generation (if acceptable). Additionally, the asymmetric deviation brings a strong asymmetry into the instantaneous forces during one flapping cycle. The underlying lift-enhancing mechanism is explored by examining the dominant vortex structures in the adjacent flow field of the wing, which is mainly attributed to the changes in the effective angle of attack, increasing with downward deviation and decreasing with upward deviation.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-25T07:33:25Z
      DOI: 10.1177/09544100221103477
       
  • S-duct flow distortion with non-uniform inlet conditions

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      Authors: Matteo Migliorini, Pavlos K Zachos, David G MacManus, Pierre Haladuda
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Convoluted aero-engine intakes are often required to enable closer integration between engine and airframe. Although the majority of previous research focused on the distortion of S-duct intakes with undistorted inlet conditions, there is a need to investigate the impact of more challenging inlet conditions at which the intake duct is expected to operate. The impact of inlet vortices and total pressure profiles on the inherent unsteady flow distortion of an S-duct intake was assessed with stereo particle image velocimetry. Inlet vortices disrupted the characteristic flow switching mode but had a modest impact on the peak levels and unsteady fluctuations. Non-uniform inlet total pressure profiles increased the peak swirl intensity and its unsteadiness. The frequency of swirl angle fluctuations was sensitive to the azimuthal orientation of the non-uniform total pressure distribution. The modelling of peak distortion with the extreme value theory revealed that although for some inlet configurations the measured peak swirl intensity was similar, the growth rate of the peak values beyond the experimental observations was substantially different and it was related with the measured flow unsteadiness. This highlights the need of unsteady swirl distortion measurements and the use of statistical models to assess the time-invariant peak distortion levels. Overall, the work shows it is vital to include the effect of the inlet flow conditions as it substantially alters the characteristics of the complex intake flow distortion.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-24T11:05:35Z
      DOI: 10.1177/09544100221101669
       
  • Long short-term memory neural network with scoring loss function for
           aero-engine remaining useful life estimation

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      Authors: Li-Hua Ren, Zhi-Feng Ye, Yong-Ping Zhao
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Estimation of the aero-engine remaining useful life (RUL) is a significant part of prognostics and health management (PHM) and the basis of condition-based maintenance (CBM) which can improve the reliability and economy. Multiple operating conditions, nonlinear degradation, and early prediction are significant and distinctive issues compared with other prognostics problems. While these issues do not get enough attention and researches in aero-engine RUL estimation. In view of these points, three specific data preparation approaches and a novel loss function are introduced. The data preparation approaches can extract high-quality data for the long short-term memory (LSTM) neural network according to the characteristic of aero-engine degradation data. Among these approaches, operating condition normalization is an effective method to handle the multiple operating conditions problems, and RUL limitation identification is a novel method to identify the turning point of the nonlinear degradation process. The scoring function is an innovative loss function used to replace the mean square error (MSE) loss function which has a preference for early prediction. The comparisons with the original LSTM and some other approaches indicate that the combination of the data preparations and the scoring loss function is an effective solution for the above issues, and can achieve the best performance among the approaches.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-24T09:09:24Z
      DOI: 10.1177/09544100221103731
       
  • Objective comparison of numerical spin study with aircraft model
           free-flight spin tests

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      Authors: Bilal Malik, Jehanzeb Masud, Suhail Akhtar
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper reports on the results of a research project that investigated the spin and recovery characteristics of a multirole fighter aircraft. In the first phase, numerical/computational methods were used to predict full scale aircraft spin and recovery characteristics. The aerodynamic data used in the numerical study was obtained from rotary balance steady coning and oscillatory coning motion dynamic wind tunnel tests conducted on 1/13th scale aircraft dynamic model. All the possible steady spin modes were numerically computed, a complete set of dynamic modes of the spinning aircraft were evaluated and six degree of freedom simulations of predicted flat spins were performed to investigate their dynamic stability and recovery characteristics. In the second phase, free-flight spin trials were conducted using 1/5th scale dynamic model of the understudy aircraft to validate the results of the analytical spin studies. Dynamic characteristics of the analytically predicted flat spins were objectively compared with flat spins found in free-flight spin trials as a validation process. Our results reveal that the numerically predicted full scale aircraft spin and recovery dynamic characteristics correlate well with those estimated from model test flights. The present study is an important step toward objective comparison of numerical spin studies based on dynamic wind tunnel tests data with free-flight spin trials, yielding important guidelines and results for future aircraft spin studies.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-23T02:09:48Z
      DOI: 10.1177/09544100221103011
       
  • 4-degrees of freedom attitude equations of motion: A new approach for
           simulating flexible satellite dynamics with time-varying payload despite
           time delay and disturbances

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      Authors: Shayesteh Nikpay, Mahdi Fakoor, Ahmad Kalhor
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A new approach for the pointing of satellite’s payload is improving the dynamics of satellites to more than 3-DOF. In this approach, there would be no requirement for satellite complete rotations to perform the payload’s mission. The purpose of this study is to derive Four Degrees of Freedom (4-DOF) equations of motion of a satellite and its payload. Therefore, the payload can observe an area of the earth, and simultaneously, the satellite can transfer data to the earth station. Lagrange dynamics are utilized to derive 4-DOF dynamic equations of the system. Then, the system of payload-satellite is controlled by the sliding mode control method with three different sliding functions. Environmental disturbances and appropriate time delay for Low Earth Orbit are applied to the nonlinear attitude equations. Numerical simulations demonstrate the effectiveness of the 4-DOF nonlinear dynamics of the payload-satellite system and indicate that the controller negates the effects of the nonlinear external disturbances and time delay. According to the results, the attitude states attain the reference targets of Euler angles and the time-varying payload with excellent precision and high convergence speed.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-21T05:34:41Z
      DOI: 10.1177/09544100221092189
       
  • Transonic flutter suppression with tuned mass damper by model-based
           stability analysis method

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      Authors: Luo Fuqing, Gao Chuanqiang, Lyu Zhen, Zhang Weiwei, Xu Qiannan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Flutter as a self-excited oscillation can cause catastrophic damage to the aircraft structure. Tuned mass damper (TMD) is one of the vibration suppression methods widely used in engineering. However, traditional linear aerodynamic methods are not accurate in transonic flow. In this study, we first establish an unsteady aerodynamic model of the NACA0012 airfoil using the system identification method based on the Auto-Regressive with eXogenous input (ARX) model. Then, a flutter suppression model is constructed by coupling the TMD with the aeroelastic system. The parameters of the TMD are investigated using the model-based aeroelastic stability analysis. It is found that the flutter instability mode of the original system has changed due to the participation of the TMD in the system modal coupling. The proposed reduced-order model (ROM) provides a fast stability analysis method for flutter suppression with TMD as well as significant guidance for TMD design and optimization.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-20T03:37:44Z
      DOI: 10.1177/09544100221089704
       
  • Real-time prediction for the surge of turboshaft engine using multi-branch
           feature fusion neural network

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      Authors: Xing-Long Zhang, Tian-Hong Zhang, Ling-Wei Li, Jia-Ming Zhang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The existing aeroengine instability precursor detection methods can be summarized as applying advanced signal processing technologies to various signals from the compressor test rig rather than the whole engine. Besides, these methods seriously depend on the artificial designed feature and threshold and also ignore the limit on the sensors onboard. Thus, with the help of the powerful feature extraction ability of the deep neural network, a real-time surge prediction method based on the multi-branch feature fusion neural network (MBFFNN) is proposed. First, the dataset can be obtained by using overlapping slices to divide surge test data into a sample sequence and using complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) to label each sample precisely. Second, for each sample, the time-domain statistical parameters are calculated and the recurrence plot is obtained by using phase space reconstruction. Finally, the MBFFNN with mixed data type input is designed, and its performance is evaluated by the generated dataset. The experimental results show that compared with multilayer perceptron (MLP), long short-term memory (LSTM), and deep residual network (DRN), MBFFNN has the best performance on two datasets for different surge tests, which demonstrates that the proposed method for surge prediction can accurately judge the state of the aeroengine, identify the instability precursor before the surge, and give an early warning in advance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-19T07:33:18Z
      DOI: 10.1177/09544100221097586
       
  • Flow characteristics and separation control in a transitional twin
           air-intake

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      Authors: KrishnaKumar R Yadav, Anuj Jain, Akshoy Ranjan Paul
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Ambient air is ingested into the engine of military aircrafts using the air-intake system within a limited space. The flow non-uniformity produced in the air-intake creates flow separation and total pressure loss due to the centerline curvature and area diffusion which eventually affects its performance. The current work discusses the performance of a transitional twin air-intake without and in presence of slotted synthetic jets. The synthetic jet is employed just before the inflection at a range of velocity ratio from 1 to 10 and found that for a velocity ratio of 4.0, the pressure distortion at the aerodynamic interface plane is found minimum. Hence, the other performance parameters are computed at that optimized flow condition. The outcome of the study reveal that the static pressure is recovered by 4.61%–6.64% while the total pressure loss is decreased by 59.28%–89.95% using optimized synthetic jets for a range of Reynolds numbers.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-18T08:00:33Z
      DOI: 10.1177/09544100221103652
       
  • Unsteady and nonlinear aerodynamic prediction of airfoil undergoing
           large-amplitude pitching oscillation based on gated recurrent unit network
           

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      Authors: You Wu, Yuting Dai, Chao Yang, Guangjing Huang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a reduced-order model (ROM) based on data-driven machine learning algorithm is constructed to identify the aerodynamic forces of airfoil undergoing large-amplitude pitching oscillation. Strong nonlinearity and unsteadiness in aerodynamics is a major challenge in the prediction of aerodynamic forces. To deal with this problem, the recurrent neural network (RNN) with gated recurrent unit (GRU) is applied for nonlinear and unsteady aerodynamic identification. A motion input signal which covers a wide range of frequency and amplitude is designed to enable the ROM with generalization capability. Shear stress transport (SST) model with low-Reynolds number modification is introduced into the computational fluid dynamics (CFD) method to calculate the aerodynamic forces as the training data. The time step size and lag order of the model are determined by the frequency domain characteristics of the training data. The results suggest that the proposed ROM has a high identification precision on nonlinear unsteady aerodynamics. The well-trained ROM could accurately predict the aerodynamic forces of airfoil undergoing sinusoidal oscillations with various frequencies and amplitudes. The proposed ROM shows advantages in accuracy over other ROM techniques. The calculation speed of ROM is 69 times faster than that of CFD method on the premise of accuracy, which can be expected a good application in engineering.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-17T01:44:18Z
      DOI: 10.1177/09544100221097521
       
  • Supersonic inlet flow recognition by hybrid-mutation non-dominated sorting
           genetic algorithm with support vector machines

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      Authors: Tian-Lin Yang, Huan Wu, Yong-Ping Zhao, Hui-Jun Tan
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The recognition of supersonic inlet flow pattern has become a research hotspot in recent years. In this paper, the dual external pressure supersonic inlet is taken as the research object. To explore the flow characteristics of the inlet, time-mean processing on the inlet pressure signal collected by sensors is conducted first, and the features of the inlet pressure data in time domain and frequency domain are extracted, respectively. As feature selection (FS) plays an important role in classification tasks and has been recently studied as a multi-objective optimization problem, two objectives of FS are considered and an improved non-dominated sorting genetic algorithm NSGA2 with hybrid mutation operators using support vector machines (SVM) as classifiers is proposed, aiming to simultaneously select feature subsets and optimize SVMs hyper-parameters. In addition, a way to deal with variation transgression is proposed to make the mutation operator of the single-objective evolution fit well in the multi-objective evolution algorithm. Experimental results on 31 sensor datasets demonstrate that our proposed algorithm can achieve competitive classification accuracy while obtaining a smaller size of feature subset compared with particle swarm optimization algorithm and some multi-objective optimization algorithms using single-objective evolution mutation operators.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-16T06:50:03Z
      DOI: 10.1177/09544100221097538
       
  • Study on aerodynamic features of rod thrust vector control for physical
           applications

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      Authors: Kexin Wu
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Mechanical thrust vector control is a classical and important branch in the vectoring control field, offering an extremely reliable control effect. In this article, a simple technology using a cylindrical rod has been numerically investigated to achieve jet controls for three-dimensional conical axisymmetric nozzles. Complex flow phenomena caused by the cylindrical rod on a flat plate and in a converging–diverging nozzle are elucidated with the purpose of a profound understanding of this technique for physical applications. Published experimental data are used to validate the dependability of current CFD results. A grid sensitivity study is carried through and analyzed. The result section discusses the impacts of three factors on performance, involving the rod penetration height, rod location, and nozzle pressure ratio. Significant vectoring performance variations and flow topologies descriptions are illuminated in full detail. When the rod penetration height changes, this technique has an effective control range, namely H/Rt ≤ 0.4. In this effective control range, the vectoring angle and efficiency increase and the thrust coefficient decreases with a deeper rod insertion. As the rod location moves downstream towards the nozzle exit, the vectoring angle increases and the thrust coefficient decays. Moreover, the direction of jet deflection remarkably varies for diverse rod locations. While the nozzle pressure ratio increases, the vectoring angle initially increases to reach the maximum level and then decays slightly. Meanwhile, the thrust coefficient continuously increases.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-16T03:29:22Z
      DOI: 10.1177/09544100221095363
       
  • High-efficiency hybrid trim method for CFD simulation of rigid coaxial
           rotor

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      Authors: Haotian Qi, Ping Wang, Linsong Jiang, Yang Zhang, Liangquan Wang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to solve the trim problem of computational fluid dynamics (CFD) simulation for rigid coaxial rotor, a hybrid trim model coupling CFD method and high-efficiency model (blade element theory) is established. In the trim process, the Jacobian matrix is solved by the high-efficiency model, while the CFD solver is only called for rotor performances modifying after each trimming step. The influences of pseudo time step, number of CFD revolution, and inflow model are investigated. Validation cases of AH-1G and Harrington-1 rotors are carried out, and good agreements are obtained. Results show that the trim efficiency can be significantly improved by saving the calculation of CFD for the Jacobian matrix. The trim accuracy is guaranteed by the correction operation with the CFD solver at each step. Moreover, as only time-averaged rotor performances are useful for trim, the efficiency can be further improved by adopting appropriately small pseudo time step and CFD revolution. The hybrid trim model has high robustness. The accuracy of inflow model for the coaxial rotor affects the convergence speed, but the final convergence can be achieved generally.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-15T03:24:13Z
      DOI: 10.1177/09544100221095369
       
  • Robust adaptive sliding mode control strategy of uncertain nonlinear
           systems

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      Authors: Yassine Soukkou, Mohamed Tadjine, Quan Min Zhu, Mokhtar Nibouche
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a robust adaptive sliding mode controller scheme as applied to a class of uncertain nonlinear systems with parametric uncertainties and external disturbances. First, a sliding mode control technique is designed. Then, the proposed robust adaptive control schemes are applied to estimate the parametric uncertainties and the upper bound value of the external disturbances by using adaptive laws, ensure robustness in presence of parametric uncertainties and external disturbances, and reduce chattering problem by introducing an hyperbolic tangent function. Lyapunov stability theory is used to analyze the stability of the closed-loop system. As an exemplar, the schemes have been applied to a quadrotor unmanned aerial vehicle (QUAV) model. Simulation results for the control of the QUAV model are provided to illustrate the performance of the proposed robust adaptive sliding mode control scheme and demonstrate that the proposed method has good tracking performance. The simulation results clearly prove the effectiveness of our approach.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-12T09:13:35Z
      DOI: 10.1177/09544100221091325
       
  • Aerodynamic effects of surface deformities on aerofoils for low-speed
           stratospheric flight

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      Authors: Jeremy Kimmons, Peter Thomas, Simone Colonia
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      High-altitude pseudo-satellites are an expanding focal area of the aerospace industry which require new technologies and manufacturing processes to reduce weight and increase efficiency with the aim of increasing endurance. One such process has resulted in the occurrence of small deformities along the leading edge of a lightweight unmanned aerial vehicle structure with the application of its skin, which may have a detrimental impact on its performance and efficiency. This paper focuses on the effects of these manufacturing deformities on the aerodynamic performance of the vehicle’s aerofoil when operating in low Reynolds number flow with the intention of identifying any detrimental flow variation. This analysis is achieved by comparing the lift curve, drag polar and pressure coefficient of both the deformed and undeformed cases of two aerofoils: a SG6042 and a GOE 523. This is accompanied with an examination of the local flow conditions scrutinising the near-wall y+ and turbulent kinetic energy calculations. The investigation finds that in two-dimensional flow, the deformities replicate the effects of transition trips in the shrinking or elimination of laminar separation bubbles. At Reynolds numbers below 250,000, the deformities reduce the net drag while leaving the lift largely unaffected. However, as a result, there is a slight shift in the minimum power condition in the order of 8% which would produce some performance loss for power efficiency and endurance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-11T07:22:04Z
      DOI: 10.1177/09544100221093210
       
  • Research on the flow field and film cooling effectiveness of the endwall
           with swirling film cooling

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      Authors: Jian Zhang, Qun Zheng, Zhaolin Li, Guoqiang Yue, Yuting Jiang
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to obtain the effect of endwall secondary flow on the swirling film cooling, a geometric model of cascade is established to research the endwall swirling film cooling and swirling flow induced by prismatic jet impingement configurations. Numerical simulation is applied to investigate three jet flow configurations on the endwall film cooling performance at the compound angles of film hole γ = 0° and 30° and blowing ratios M = 0.5–2.0. The influence of complex vortex structures near endwall for jet flow is analyzed in detail; the strong transverse cross flow near the endwall is the main reason affecting the film cooling effectiveness. The variation laws of endwall film cooling effectiveness with the compound angle of film hole, jet flow configuration, and the blowing ratio are obtained. As the blowing ratio increases, the spanwise average film cooling effectiveness increases first and then decreases. While the blowing ratio is M =1.0, the endwall film cooling effectiveness is the best. Increasing the compound angle of the film hole leads to a decrease in the endwall cooling effectiveness. The spanwise average cooling effectiveness of γ = 30° decreases by 35% compared to the γ = 0°.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-11T05:33:22Z
      DOI: 10.1177/09544100221097527
       
  • Effects of circular and non-circular nozzle exit geometries on subsonic
           and supersonic jet propagations

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      Authors: Thillaikumar Thangaraj, Mrinal Kaushik, Thanigaiarasu S
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The mixing enhancement and core length reduction of a jet without significant loss of thrust are essential for reducing infrared radiation, mitigating aeroacoustic noise, improving combustion characteristics, and thrust vectoring. The jet mixing can be improved by manipulating the flow behavior. In subsonic and sonic jets, the flow manipulation may be achieved by utilizing nozzles with non-circular geometries that shed vortices of varying size due to their non-uniform azimuth curvatures. Non-uniform vortices generate differential spreading along the nozzle’s perimeter, causing axis switching and improving entrainment characteristics. Therefore, the present study examines the effects of two non-circular nozzle exit shapes (elliptic and square) on the mixing augmenting efficacy at subsonic and sonic flow conditions. The circular nozzle is tested for comparison. Both quantitative and qualitative analyses evaluate the efficacy of nozzles with non-circular exit geometries. Among the configurations investigated, the elliptic nozzle is superior in shortening the potential core length and enhancing the jet spread. A maximum reduction of 18.75% in core length with rapid jet decay was accomplished with the elliptic nozzle. The measurement of pressure profiles at different streamwise locations reveals that the spread rate is greater for elliptic and square jets than their circular counterpart. The elliptic jet exhibits the highest spread along the minor-axis direction compared to the major-axis direction. The differential jet spread rate in the elliptical jet causes an early axis-switching––direct evidence of mixing augmentation. Shadowgraph images show the asymmetric pattern of shock cell structures and differential spreading in elliptic and square jets.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-10T06:26:38Z
      DOI: 10.1177/09544100221097537
       
  • Initial weight estimation of twin-fuselage configuration in aircraft
           conceptual design

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      Authors: Yiyuan Ma, Jin Yan, Ali Elham
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The Ultra-High Aspect Ratio Wing (UHARW) concept can improve the aircraft’s aerodynamic efficiency and reduce fuel consumption. The Twin-Fuselage (TF) configuration is one of the promising concepts for the UHARW design to reduce the wing bending moments and shear forces. This paper presents the development of a semi-empirical method for the weight estimation of TF aircraft in the initial sizing stage. A physics-based wing weight estimation method is improved for higher fidelity aerodynamic analysis and modified for composite material structures of TF aircraft. This method is used in the design of experiments and the results are applied for regression analysis to establish a semi-empirical method. Eventually, the established semi-empirical weight estimation method is integrated into a TF aircraft conceptual design and performance analysis framework. A mid-range TF aircraft and a long-range TF aircraft are designed and sized to illustrate its application and efficiency in rapidly estimating the TF aircraft weight breakdown.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-07T01:49:30Z
      DOI: 10.1177/09544100221095370
       
  • A general real-time optimization framework for polynomial-based trajectory
           planning of autonomous flying robots

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      Authors: Yunes Sh. Alqudsi, Ayman H Kassem, Gamal El-Bayoumi
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents a general real-time, numerically stable optimization framework for time polynomial-based trajectory generation of autonomous aerial robots. The proposed general optimization framework (GOF) allows various optimization criteria for trajectory generation cost-function, such as minimizing the trajectory total length, time, and position derivatives. Minimizing position derivatives includes velocity, acceleration, jerk, and snap, or any combination of them. This study considers the quadrotor as the test platform. By exploiting tools from the calculus of variations, differential flatness property, and polynomial-based trajectories, the developed algorithm finds feasible trajectories without extensive computational sampling and iterative searching in the high-dimensional state space of quadrotor dynamics. The GOF includes a segment-wise gradient descent-like algorithm to iteratively decrease the allowed time of each segment individually so as to avoid getting stuck at a local minimum. The comparison analysis with existing methods validated the numerical stability and computational speed advantages of the proposed approach. It also shows that the algorithm is suitable for the real-time generation of high-performance long-range trajectories consisting of a large number of waypoints and high-order piecewise polynomials. An animated simulation of this work is available at https://youtu.be/E1AC1vyPqOE
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-04T06:23:39Z
      DOI: 10.1177/09544100221090690
       
  • High-altitude airship propulsion system optimal design and experiment
           based on energy balance

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      Authors: Wang Dongchen, Song Bifeng, Jiao Jun, Wang Haifeng
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes a propulsion optimization method with the surrogate modeling technique based on the coupling relationship between the propulsion and energy subsystem to achieve high-altitude airship weight reduction and figure out key factors. Propeller and motor surrogate models were constructed based on an inhouse fluid-structure solver and validated by the wind tunnel experiment. Solar intensity variation, solar cell distribution, and energy balance were modeled for the calculation of energy system weight. By minimizing the total weight of propulsion end energy subsystem as the goal and energy balance as the constraint, an optimization architecture was built. And a typical high-altitude airship is optimized as an example. Propulsion design variables were analyzed to figure out the influence on the airship’s overall performance. The results show that introducing energy balance into propulsion system optimal design can effectively reduce the total weight of the propulsion and energy system.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-23T09:22:12Z
      DOI: 10.1177/09544100221089700
       
  • Flight performance of helicopter tail rotors with extendable chord

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      Authors: Kelong Yang, Dong Han
      First page: 3091
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To investigate the potential of Statically and Dynamically Extendable Chord (SEC/DEC) in performance improvement of helicopter tail rotors, a prediction model of helicopter flight performance is developed and validated. It is suitable to deploy the SEC and DEC close to the blade tip for power reduction of tail rotor in hover and high-speed flight. The deployment locations of SEC and DEC for tail rotors are similar to that of main rotors. In hover, the deployment of the SEC and DEC results in little power reduction. From low to medium speed flight, the deployment of the DEC and SEC increases the power. In high-speed flight, the SEC and DEC can significantly decrease the power, especially at a large take-off weight. At 300 km/h, when the chord extension is 20% of blade chord, the SEC and DEC with 1/rev input decrease the power by 14.44% and 20.47% at a take-off weight coefficient of 0.0091. The DEC shows greater potential in power reduction than the SEC. There is an optimal phase input for the maximum power reduction, which does not vary with forward speed. For the DEC with 1/rev input, the optimal phase is [math]. The optimal phase input for the maximum power reduction of tail rotors is different from that of main rotors.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-26T02:23:35Z
      DOI: 10.1177/09544100221080142
       
  • Nonlinear aeroelastic stability analysis of a two-stage axially moving
           telescopic wing by using fully intrinsic equations

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      Authors: Sayed Hossein Moravej Barzani, Hossein Shahverdi, Mohammadreza Amoozgar
      First page: 3102
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      During the process of span extension for an aircraft wing equipped with a telescopic morphing mechanism, the wing aspect ratio increases, and hence, the geometrical nonlinearities might become more significant. In this regard, this paper aims to investigate the effect of structural nonlinearity on the aeroelasticity of span morphing wings using the exact fully intrinsic equations for the first time. Furthermore, the effects of various parameters such as thrust force, engine location, chord size, flight altitude, initial angle of attack, and overlapping mass on the aeroelasticity of the wing are studied. The applied aerodynamic loads in an incompressible flow regime are determined using Peters’ unsteady aerodynamic model. In order to check the stability of the system, first the resulting nonlinear partial differential equations are discretized by using the central finite difference method and then linearized about the static equilibrium. Finally, by obtaining the eigenvalues of the linearized system, the stability of the wing is evaluated. It is observed that by using the fully intrinsic equations, the instability of the axially moving telescopic wing can be determined more accurately. Moreover, the results show that the morphing length and overlapping mass have significant effects on the aeroelastic stability of the telescopic wing.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-28T09:13:41Z
      DOI: 10.1177/09544100221080117
       
  • A structural design approach for a droop nose morphing demonstrator with
           shape memory alloy patches

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      Authors: Dimitrios G Stamatelos, Vassilios Kappatos
      First page: 3111
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      An innovative concept has been devised for assisting an actuator to morph a Droop Nose (DN) structure, which is comprised from the skin and three longitudinal omega stringers. The concept is based on the development of a suitable composite patch, with embedded shape memory alloy (SMA) wires, and the appropriate design of a DN configuration for morphing purposes. The integration of composite patches, to the DN structure, has a dual innovative role: (a) it can either provide/extend the morphing capabilities of the structure, in terms of displacement or (b) it can reduce the required actuation forces for obtaining morphing of the DN structure. For determining the most suitable DN configuration, for the application, a sensitivity analysis, with the aid of ANSYS finite element (FE) software and a design of experiments (DoE) approach, has been carried out. The investigated parameters (geometrical and lamination characteristics) are selected to vary the stiffness of the DN structure. Additionally, a numerical parametric FE model, of the SMA patch and its configuration, is developed and analysed. The developed FE models simulated the shape memory effect of SMA wires considering their activation temperature and hence their thermo-mechanical behaviour. Eventually, a possible integration of the SMA patches to the DN structure is proposed and the respective remarks are highlighted.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-29T10:07:10Z
      DOI: 10.1177/09544100221080116
       
  • Macroscopical contact pressure and microscopic leakage performance
           analysis of rubber seal considering thermal oxygen aging effect

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      Authors: Heng-Chao Sun, Yan-Yan Hao, Li-Na Wang
      First page: 3129
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Leakage performance of rubber seal is a key factor of spacecraft system, which is required long life. But the degradation law of the rubber seal performance in long service period is limited to qualitative analysis for its macro contact performance, and the quantitative research of rubber seal leakage performance is rarely involved considering thermal oxygen aging effect. Therefore, the thermal oxygen aging mathematical model is firstly established to predict the life of rubber material by aging tests. Secondly, the finite element model (FEM) of rubber seal performance analysis considering thermal oxygen aging effect is built to obtain the degradation law of its macroscopic contact performance with the increase of service time. Thirdly, the micro-leakage model of rubber seal considering thermal oxygen aging effect is established based on the material surface microstructure, contact pressure, and contact width, and the leakage rate of rubber seal is calculated by the model. Finally, the micro-leakage model of rubber seal is modified based on the experimental results, so the calculation accuracy of leakage rate is improved.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-03-24T05:24:26Z
      DOI: 10.1177/09544100221080504
       
  • Risk identification of civil aviation engine control system based on
           particle swarm optimization-mean impact value-support vector machine

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      Authors: Jing Cai, Han Bao, Yan Huang, Di Zhou
      First page: 3141
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The actual risk of the engine control system in operation is often higher than expected risk level, which brings hidden dangers to the safe operation of aircraft. Therefore, a PSO-MIV-SVM (particle swarm optimization-mean impact value-support vector machine) model is proposed to identify the risk of engine control system. Firstly, seven characteristic variables are extracted through the analysis of engine unsafe information, and 810 typical engine event samples were selected and normalized. Secondly, the SVM-based engine control system risk identification model is established and optimal kernel function of the SVM model is selected. Thirdly, the SVM-MIV method is used to sort the importance of the seven characteristic variables, and the identification accuracies of different characteristic variable groups are calculated to obtain the optimal combination of characteristic variables. Finally, the parameters of the SVM model are optimized by using the PSO algorithm and the accuracy of the PSO-MIV-SVM model for the risk identification of the engine control system reaches 93.58%.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-06T04:10:29Z
      DOI: 10.1177/09544100221080767
       
  • A new strategy for solving store separation problems using OpenFOAM

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      Authors: Saleh Abuhanieh, Hasan U. Akay, Barış Bicer
      First page: 3152
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The ability of OpenFOAM to solve the problem of a store separating from an air vehicle (store separation problem) has been evaluated using a dynamic mesh (Overset/Chimera) technique for an industry-class (transonic and generic) benchmark test case. The major limitations of the standard libraries have been determined. To tackle these challenges, a new strategy has been proposed and implemented using only open-source libraries and tools. The strategy combines porting, modifying, and adapting an overset library from the OpenFOAM fork platform (foam-extend) to the standard OpenFOAM platform (ESI). Furthermore, in order to overcome the well-known weakness of the standard OpenFOAM compressible solvers, the newly adapted overset library was integrated with an open-source, density-based, and coupled solver (HiSA), which uses the OpenFOAM technology. Additionally, a force restrained model was developed to consider the externally applied forces on the store by the store ejectors. The accuracy of the developed strategy has been compared with wind tunnel tests and the solutions of two well-known commercial codes, showing good agreements with them. While the study has focused on simulations with inviscid Euler equations (typical of the test case considered here), the viscosity effect on the solution has also been studied with Navier–Stokes equations and compared with other results in the literature, showing minor differences. To the best of the authors’ knowledge, this is the first work which studies and validates the store separation problem in transonic regime with OpenFOAM.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-11T08:12:56Z
      DOI: 10.1177/09544100221080771
       
  • Uncertainty quantification of aeroelastic wings flutter using an optimized
           machine learning approach

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      Authors: Mohsen Rezaei, Kourosh H Shirazi, Hamed H Khodaparast
      First page: 3167
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This study outlines the flutter characteristics of aeroelastic wings under unsteady aerodynamic loading based on an efficient support vector machine assisted k-method. First, the aeroelastic wing flutter speed and flutter frequency are obtained using k-method. Then, the uncertain input parameters distribution is modeled by probability density functions. These parameters are propagated to the aeroelastic wing equations. The Monte Carlo simulation using 12 parallel logical threads is carried out to obtain the flutter speed and the flutter frequency distribution. An optimal robust surrogate model is trained by limited numbers of input and output using support vector machine. Monte Carlo simulation is also carried out in conjunction with the machine learning based k-method computational framework for obtaining the complete probabilistic description of flutter speed and flutter frequency. The coupled support vector regression based k-method is a novel approach that is first used in the aeroelastic wings flutter. The present method is found to reduce the computational time and cost significantly without compromising the accuracy of results.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-23T12:47:52Z
      DOI: 10.1177/09544100221080765
       
  • Active nonlinear vibration control of a membrane solar array structure

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      Authors: Xiang Liu, Lianglinag Lv, Guoping Cai
      First page: 3186
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Membrane solar array has attracted a lot of attentions in recent years because of the advantage of light-weight, low-cost, and high-folding-ratio. Meanwhile, the membrane solar array structure also pose challenging large-amplitude vibration issue which will impact the performance of the spacecraft significantly. In this paper, active nonlinear vibration control of a membrane solar array structure is studied. Based on the nonlinear finite element method, a nonlinear dynamic model of the structure is established. The optimal positions of piezoelectric actuators are determined by optimizing a controllability optimization criterion with Particle Swarm Optimizer algorithm. An active controller is designed to suppress the undesired nonlinear vibration based on the linearized dynamic model by using the LQR control method. Simulation results show that the designed active controller can suppress the nonlinear vibration of the membrane solar array structure effectively, and the optimally placed actuators can produce better control effect with smaller control inputs.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-10T11:06:20Z
      DOI: 10.1177/09544100221081518
       
  • A novel solution methodology for longitudinal flight characterization of a
           Flying-Wing Micro Aerial Vehicle

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      Authors: Taimur Ali Shams, Syed Irtiza Ali Shah, Aamer Shahzad, Muzaffar Habib, Farhat Asim, Mohtashim Mansoor
      First page: 3201
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      A longitudinal flight dynamic study of a low mass moment of inertia vehicle is presented. Aerodynamic and stability derivatives of a flying-wing microaerial vehicle (FWMAV) were obtained through detailed subsonic wind tunnel tests at a Reynolds Number of 1.87 × 105. Rate and acceleration derivatives were obtained using the potential flow solver, Tornado®. A novel methodology for the estimation of dimensional derivatives is proposed, and results are compared with the conventional linear time-invariant systems (LTI) approach. Free response for natural frequency, damping coefficient, and time constant as well as forced response upon a unit step and a unit impulse elevon input has been calculated and analyzed. The proposed methodology predicted two pairs of complex conjugates for the longitudinal flight up to a pitch angle of 89° whereas the conventional methodology predicted the same up to 57°. Longitudinal modes sensitivity in terms of stability with the variation of mass, velocity, and pitch angle has also been analyzed. The flying-wing microaerial vehicle was able to sustain straight and level flight during flight trials; however, higher frequencies of phugoid and short period modes were observed. These high frequencies were the consequence of large magnitude of [math] (ratio of Z-force derivative with the angle of attack and cruise velocity) and [math] (ratio of Z-force derivative with the axial velocity and cruise velocity). It is concluded that the proposed methodology presented a more realistic representation of longitudinal flight modes since classical flight modes are captured till 89° which conventional LTI methodology failed to do so.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-27T08:19:57Z
      DOI: 10.1177/09544100221081845
       
  • Nonlinear analysis and control of an underactuated 3-DOF control moment
           gyroscope with experimental validation

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      Authors: Gobiha D, Rohith G
      First page: 3220
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Nonlinear controllers have been extensively abstracted in recent times. Nevertheless, real time implementation for underactuated MIMO physical systems is rarely attempted. This work proposes a nonlinear framework based on dynamical analysis and the sliding mode based control technique to control a highly coupled and nonlinear MIMO underactuated control moment gyroscope. First, an analytical formulation based on dynamic characterization is proposed to understand both the unactuated dynamics and the performance constraints of the gyroscope. This characterization helps in designing a feasible nonlinear sliding mode controller which helps in a simple and straightforward control of the system through the entire operating regime. The effectiveness of the proposed nonlinear control and analytical framework is established by successful implementation on the experimental gyroscope setup.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-04T06:34:35Z
      DOI: 10.1177/09544100221081820
       
  • Gravity-compensated guidance for impact-angle interception of a moving
           target

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      Authors: Hyeong-Geun Kim, Jun-Yong Lee, Pyojin Kim
      First page: 3233
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes an impact-angle control guidance (IACG) law for anti-ship and anti-tank missiles in which the command converges to zero at the point of interception, even in a gravity field. The desired line-of-sight (LoS) angle that satisfies the terminal impact-angle and acceleration constraints is first defined. The guidance command is then derived as a solution that realizes the convergence of the actual LoS angle to the desired LoS angle during the terminal stage of homing in on a target. Gravity is considered when designing the guidance law such that the desired terminal constraints are accurately satisfied, even under realistic pitch-axis engagement. We also investigated whether the proposed law is optimal for minimizing the total expense of maneuvering while performing IACG in a gravity field. The results of the numerical simulations included in this study demonstrate that the proposed guidance law achieves accurate impact-angle interception with the command converging to zero at the end of homing.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-04T10:03:50Z
      DOI: 10.1177/09544100221082101
       
  • Combined application of passive and active boundary layer aspiration in a
           transonic compressor rotor for shock wave/boundary layer interaction
           control

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      Authors: Xiaoxiao Zhou, Qingjun Zhao, Ben Zhao, Qiangren Xu, Wei Zhao
      First page: 3243
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Shock wave/boundary layer interaction (SWBLI) is one of the key factors that limits the improvement of aerodynamic performance and stability for supersonic/transonic compressors. In this research, a combined flow control device (CFCD) was designed for controlling SWBLI in the NASA transonic compressor Rotor 35. The original flow fields for Rotor 35 were numerically analyzed first. The results show that the SWBLI is severe, resulting in much flow loss and partly leading to the compressor instability. Based on this phenomenon, the CFCD was designed with a novel three-dimensional passive self-recirculation flow channel and an active suction slot. The flow channel is mounted on the rotor blade suction surface to connect the low- and high-pressure regions ahead of and behind the shock, respectively. The effect of the CFCD on the rotor performance and corresponding working mechanism are then researched as well. With the help of CFCD, the rotor-achieved total pressure ratio (TPR) is maximally increased by 3.0%, and the stall margin (SM) is improved by 4.1% as well. But the rotor isentropic efficiency (IE) considering additional energy expenditure caused by active suction flow has the maximum increment at choke point of 0.27% and highest reduction at near-stall point of 0.54%. The working mechanisms of CFCD include two aspects: one is forming a stable and low-entropy generated lambda shock wave and the other one is reducing the magnitude of flow separation. The dominant mechanism varies with the rotor working condition and depends on whether the leading-edge shock moves upstream of the passive bleed slot.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-21T12:51:31Z
      DOI: 10.1177/09544100221082332
       
  • Numerical estimation of longitudinal damping derivatives of a flying wing
           micro aerial vehicle

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      Authors: Taimur A Shams, Syed Irtiza Ali Shah, Aamer Shahzad, Kashif Mehmood
      First page: 3261
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Longitudinal damping derivatives, [math], of an aerial vehicle is important from an aerodynamic stability point of view. Experimental calculation of longitudinal damping derivatives using wind tunnel is not a cost-effective method; therefore, researchers have developed numerical solutions as an alternative. In this research, the longitudinal damping derivatives of a flying wing micro aerial vehicle (FWMAV) were calculated using numerical simulations by adopting pull-up maneuver and forced harmonic motion in pitch axis. Pull-up maneuver with four steady rotational rates was simulated to obtain pitch rate derivative, Cmq. Combined derivative, [math], was obtained by simulating forced harmonic motion of FWMAV around a mean angle of attack of 0° with amplitude of oscillation of ± 3° using four reduced frequencies (0.02, 0.03, 0.04, and 0.05). Unstructured surface and volume mesh was used in a spherical domain engulfed inside a large cuboid domain for moving reference frame strategy. Reynolds number taking mean aerodynamic chord as a reference length was 2.33 × 105. Spalart–Allmaras turbulence model was used. Pitch rate derivative, combined derivative, and acceleration derivative were found as − 0.03/rad, − 7.39/rad, and − 7.36/rad, respectively, by the use of a phase method at a reduced frequency of 0.03. During flight dynamic analysis, it was found that [math] has a significant contribution on damping in short period mode with no effect on Phugoid mode. The research concluded that for tailless configurations, acceleration derivative [math] can exist and can provide necessary damping in the longitudinal flight mode.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T12:14:10Z
      DOI: 10.1177/09544100221082856
       
  • Adaptive Kalman filter based on multiple fading factors for fast in-motion
           initial alignment with rotation modulation technique

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      Authors: Jianguo Liu, Xiyuan Chen
      First page: 3281
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a novel fast fine alignment method is proposed on the basis of micro electro mechanical systems (MEMS) for unmanned aerial vehicle (UAV) under mooring conditions. Firstly, the model of single-axis rotation modulation with extended angular rate measurement is built to improve the speed of convergence, especially the azimuth misalignment angle and the constant error of gyroscope along the rotation axis. Both model mismatch and noise uncertainty of the extended measurement will arise for the difficulty to obtain the exact angular velocity of the carrier without auxiliary sensors. To address this problem, the adaptive Kalman filter based on multiple fading factors is proposed. Besides, the meta-heuristic beetle antennae search (BAS) algorithm is applied for the first time to optimize the fading factors in real time. Then, the effectiveness of the proposed method is verified by means of singular value decomposition and error covariance matrix analysis. Finally, the result of comparative simulations and experiments show that the observability degree and convergence speed of misalignment angles improve significantly compared to those conventional methods and the estimated values can satisfy the requirements of fine alignment. More importantly, the constant error of gyroscope along the rotation axis is estimated accurately and can be compensated in the subsequent navigation process.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-18T12:20:05Z
      DOI: 10.1177/09544100221082802
       
  • Effects of canard oscillations on the unsteady flowfield over the wing in
           supersonic flow

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      Authors: Ali R Davari, Mohammad R Soltani
      First page: 3293
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Few studies have been devoted to effects of canard oscillations on the flowfield over the wing in supersonic flow and the associated time lags. In this article, an in-depth experimental study on a closely coupled canard-wing-body configuration in supersonic flow has been undertaken to mark the zone of influence of the oscillatory canard on the wing. Surface pressure measurements have been performed on the wing downstream of canard in both static and oscillatory cases at various wing angles of attack and canard deflection angles as well as the canard oscillation amplitudes and frequencies. The results show that the upwash and downwash flowfields due to an oscillatory canard periodically change the effective angle of attack seen by the wing and have different effects on various regions. In supersonic flow, the pressure rise due to the oblique shock waves causes the primary flow separation and the vortex break down onsets to occur at higher angles of attack, comparing to those in the lower speed regimes. According to the results, the mid-span region on the wing, which is directly in the shadow of the oscillating canard, receives more disturbances. During upstroke, the canard induces a downwash field to the front half of the wing, while in downstroke motion, the front regions of the wing experience upwash flow, giving rise to the effective angle of attack seen by the wing. Among various oscillation parameters, the pitching amplitude was observed to have a strong impact on the time lag in flowfield over the wing.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-09T02:20:55Z
      DOI: 10.1177/09544100221083348
       
  • Effects of different structural parameters on the 7075-T651 aluminum alloy
           lug structure fatigue life

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      Authors: Li Hui, Hongda Wang, Yanqing Huang, Wenjun Yang, Song Zhou
      First page: 3304
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Lug structure is an important connection structure in aviation aircraft. However, fatigue cracks are easily generated during the service of the aircraft. Therefore, this study aims to explore the influence of different structural parameters on the fatigue life of the 7075-T651 aluminum alloy lug, using experimental and numerical methods to determine the effects of these structural parameters. Scanning electron microscopy was employed for fracture analysis, and three-dimensional finite element models were used to solve the holes edge stress distributions under peak load and stress concentration factor. The results indicate that the fatigue life of the lug increases with the increase in the extrusion projection area and the included angle of the outer edge, and the impact of the extrusion projection area on the fatigue life of the lug is greater than the angle of the outer edge, and the fatigue life of the lug does not change with the change of the chamfer at the bottom. The peak stress at the root of the lug hole becomes the main factor affecting the fatigue life of the lug, and the crack always expands along the net cross-section of each parameter lug.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T01:14:28Z
      DOI: 10.1177/09544100221083354
       
  • Effects of fusion height of tip winglet on the clearance flow in a
           compressor cascade

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      Authors: Wenfeng Xu, Peng Sun, Jingjun Zhong, Shaobing Han, Guogang Yang
      First page: 3313
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The leakage flow generated by rotor clearance seriously affects efficiency and stability of a compressor. In order to reduce the effect of leakage flow, the tip winglet has been applied at the tip of a transonic compressor cascade. Numerical simulation has been used to investigate the influence of tip winglets with different fusion heights on the flow field structure. Furthermore, the effect of winglets was analyzed under different clearance heights and incidence angles. Results reveal that the winglet can weaken the kinetic energy of the leakage flow. The development of the leakage vortex along the pitchwise is suppressed, and the total pressure loss is decreased near the tip. The increase in the tip separation vortex scale leads to a remarkable decrease in the leakage flow rate. With the increase in fusion height, the scale of tip separation vortex decreases gradually, and the suppression effect on the leakage flow rate is weakened. The optimal scheme can reduce the loss by 3.3% and leakage flow rate by 13.4%. The suppression effect of the winglet on flow loss increases gradually with the increase in incidence angle. Moreover, the suppression effect of the winglet on leakage flow and flow loss increases first and then decreases with the increase in tip clearance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-04T05:29:05Z
      DOI: 10.1177/09544100221083346
       
  • Integrated impact time guidance and control against non-maneuvering
           targets

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      Authors: Aditya Patil, Shashi Ranjan Kumar
      First page: 3327
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper proposes integrated guidance and control for skid-to-turn cruciform canard-controlled interceptors for controlling impact time along with interception of non-maneuvering targets. This approach circumvents the possible difficulties associated with designing guidance and control subsystems independently. An interceptor control surface deflection for achieving appropriate lateral acceleration to achieve the guidance objectives are derived using sliding-mode control considering nonlinear engagement dynamics, thereby remaining effective even for engagement with large initial heading errors. The switching surface is chosen to be a function of time-to-go and its rate with different time-to-go estimates against stationary and moving targets. The time-to-go estimate for stationary target accounts for the heading angle errors, while that for constant velocity target provides an exact value. Unlike many of the existing strategies, the proposed approaches enable the interceptor to achieve an impact time, even less than its initial estimates. The efficacy of the proposed guidance strategies is validated through numerical simulations for various initial engagement geometries. Furthermore, the performance of the proposed integrated guidance and control approach is also compared with the separate design of guidance and control subsystems, and shown to be superior.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-19T06:41:37Z
      DOI: 10.1177/09544100221083427
       
  • Efficiency of rocket engine thrust vector control by solid obstacle on the
           nozzle wall

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      Authors: Genadii Strelnikov, Oleksandr Ihnatiev, Nataliya Pryadko, Katerina Ternova
      First page: 3344
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The thrust vector control of a rocket engine by disturbing the supersonic flow in its nozzle is used for missile development for various purposes in different countries. Disturbance of the supersonic flow in the jet engine nozzle can be caused by various obstacles on the nozzle wall: solid obstacle, liquid or gas jet, combinations of solid obstacle with injected jets. The simplest and most effective way to create a disturbance is to disturb it by setting a solid cylindrical obstacle on the nozzle wall. The high efficiency is explained by the lack of the working fluid consumption on board the aircraft to create a control force, or its minimum amount necessary to protect the obstacle from the high-temperature oncoming gas flow in the rocket engine nozzle. This paper presents the study results of gas flow simulation with cylindrical obstacle perturbation on the wall of the Laval rocket engine nozzle in its subsonic and supersonic parts. The optimal placement in the nozzle is determined to obtain the maximum lateral control force. As a result of research, it was found that the perturbation of a supersonic flow in a rocket engine nozzle by a cylindrical obstacle has practically the same character when its position changes along the length of the nozzle. In the subsonic part of the nozzle in the median plane, the perturbed pressure on the wall has a positive sign, and on the obstacle wall its sign-alternating. When an obstacle is in the subsonic part of the nozzle, the integral value of the lateral force is negative in comparison with positive for the supersonic part.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T01:53:41Z
      DOI: 10.1177/09544100221083714
       
  • Linear parameter-varying-based transition flight control design for a
           tilt-rotor aircraft

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      Authors: Shen Qu, Guoming Zhu, Weihua Su, Sean Shan-Min Swei
      First page: 3354
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper presents the development of novel transition flight controllers for a class of urban air mobility aircrafts configured with a fixed-wing and six distributed electric rotor assemblies. Only the two tilt-rotors are utilized for thrust vectoring during transition flight from hovering to steady-level flight, while the four lift-rotors are modulated with aerodynamic lift induced by fixed-wing to maintain stable altitude-hold. Three tractable tilt-rotor articulation profiles are proposed by taking into account of various aircraft and hardware constraints. Given a predefined nominal tilting profile, a family of linear models is obtained by linearizing the nonlinear aircraft model at multiple tilt-rotor angular positions along the tilting profile. Using tilt-rotor angular position as a scheduling parameter, a discrete-time linear parameter-varying model can be constructed, which is then used to develop a novel transition flight control architecture that integrates the adaptive model predictive control law with feedforward effect of the dynamic reference compensation. The simulation results demonstrate the effectiveness of proposed transition flight controllers and its robustness subject to external disturbance.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-25T12:29:02Z
      DOI: 10.1177/09544100221083713
       
  • Numerical investigation of an aggressive s-shaped compressor transition
           duct with boundary layer suction

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      Authors: Song Huang, Chengwu Yang, Ge Han, Shengfeng Zhao, Hongzhi Cheng, Xingen Lu
      First page: 3370
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Aggressive s-shaped compressor transition ducts are important components in the connection between upstream boosters and downstream high-pressure compressors. The flow path is an s-shaped channel with struts and a large radial drop length ratio, which breaks through the limitations of traditional design and has a large aerodynamic loss. Therefore, this paper considers an aggressive s-shaped compressor transition duct in a geared turbofan engine and creatively proposes a method for controlling the flow separation through boundary layer suction. The results show that hub suction reduces the losses of the aggressive s-shape transition duct. As the mass flow rate of hub suction increases, the total pressure loss coefficient decreases and the rate of reduction in the total pressure loss slows down. Combined boundary layer suction reduces the total pressure loss to a greater extent. On the premise that the location of blade suction remains unchanged, the optimal location for the circumferential slot of hub suction is at 20% of the axial chord length of the strut, whereby the total pressure loss coefficient decreases by about 30% compared with the case of no suction. When the mass flow rate of suction is fixed at 3% of the inlet mass flow rate, a distribution of 0.5% from blade suction and 2.5% from hub suction reduces the total pressure loss by 1.6% compared with the case where all 3% comes from hub suction. The distribution of the mass flow rate for combined boundary layer suction has an optimal ratio.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-12T02:30:57Z
      DOI: 10.1177/09544100221084384
       
  • Aerodynamic design and evaluation of an open-nose supersonic drone

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      Authors: Eiman B. Saheby, Anthony P. Hays, Shen Xing
      First page: 3387
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The objective of this paper is to investigate the efficiency of a proposed supersonic drone configuration, in terms of drag, ram recovery, and fundamental flight performance factors. Sustainable supersonic cruise at Mach 1.6 is the major segment of the mission profile which affects the overall geometry resulting from the conceptual design phase, a tailless delta drone with an open-nose forebody, lofted around the inlet which consists of an analytical compression surface and a S-duct diffuser. Because the aerodynamics of this unconventional configuration is unknown, a series of CFD simulations using the ANSYS Fluent solver is coupled to the design process to predict both internal and external aerodynamics as a proof of the concept. The simulations indicate that the drone’s overall drag is significantly lower than the other configurations with side or underside integrated inlets while the inlet pressure recovery is adjusted to maximize the engine thrust. The parasite drag at design speed is about 0.022 which is considerably lower than conventional configurations and the pressure recovery more than 0.96 is possible by applying the boundary layer bypass. A comparative study, with a developed thrust model, shows that the configuration satisfies mission requirements and exceeds them at transonic and supersonic flight phases.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-16T03:26:20Z
      DOI: 10.1177/09544100221084389
       
  • Data-driven fault-tolerant control for unmanned aerial vehicles without
           using identification model

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      Authors: Duo Zheng, Xinghua Xu, Defu Lin
      First page: 3411
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Unmanned aerial vehicle (UAV)’s fault-control problem was studied in this paper, and data-driven fault-tolerant control scheme was developed for acceleration tracking control of UAV in order to cope with the uncertainties induced by aerodynamic damage. A linear UAV dynamic model was given with reasonable assumptions, and the acceleration tracking control for UAV was converted to solving an infinite-horizon optimal control problem. The augmented algebraic Riccati equation (ARE) is derived, and its solution stability is proved based on Lyapunov theory. The data-driven control algorithm is further derived for online solving of the augmented ARE with only using flight data. The proposed algorithm is based on experience replay of flight data rather than model knowledge, so it greatly reduces the effect of uncertainties induced by aerodynamic damage on the flight control system for UAVs. Finally, the effectiveness of developed algorithm is verified through the numerical simulations under different uncertainties induced by aerodynamic damage.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-19T01:12:26Z
      DOI: 10.1177/09544100221084385
       
  • Loss evaluation and aerodynamics investigation of an aggressive
           intermediate turbine duct under off-design conditions

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      Authors: Kaihe Geng, Chenxing Hu, Ce Yang, Yanzhao Li, Changmao Yang
      First page: 3428
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To maximize the performance of the intermediate turbine duct (ITD) under off-design conditions, the loss generation in a one-half stage turbine was quantified using entropy generation and the global entropy generation rate. The numerical results solved by the unsteady Reynolds-averaged Navier–Strokes equations were first verified. Then, the aerodynamic losses within the high-pressure turbine stage were evaluated by efficiency loss under nine operating conditions composed of three rotor speeds and three rotor tip gaps. Finally, the disturbance modes caused by the upstream wake were captured by the dynamic mode decomposition method. Different from the influence of tip gaps, losses of the high-pressure turbine and the ITD are due to the swirl angle display an opposite trend. Under the influence of the interaction between the tip leakage flow and the shroud flow of the ITD, the viscous dissipation and turbulent dissipation increase with a larger tip gap owing to the dominant counter-rotating vortices and secondary flow occurring near the upstream of the ITD shroud. In addition, a large gap seems to enlarge the swirl component of the inflow angle, especially over 80% passage height, leading to greater dissipation losses in these areas. At the ITD inlet, two pairs of counter-rotating vortices at the shroud and the hub are, respectively, captured by the axial velocity mode. Large tip gaps enhance endwall vortices near the shroud and make the up vortex pairs merge into one pair.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-20T11:09:25Z
      DOI: 10.1177/09544100221085330
       
  • A composite controller design using an adaptive internal type-2 fuzzy
           logic system and the fixed-time disturbance observer for an air-breathing
           hypersonic vehicle with a variable geometry inlet

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      Authors: Liqian Dou, Yiqun Li, Miaomiao Du, Xiuyun Zhang, Zhiyu Li
      First page: 3444
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a novel composite controller design technique is addressed for using an adaptive interval type-2 fuzzy logic system (FLS) with the fixed-time disturbance observer (FTDO) such that the enhanced tracking performance is achieved for an air-breathing hypersonic vehicle with a variable geometry inlet (AHV-VGI). First, introducing the variable geometry inlet to take proper mass flow into the engine without any flow spillage ensures enough thrust for acceleration and maneuvering flight. The interval type-2 FLS integrated with an adaptive control algorithm is derived to approximate the complicated nonlinear items in the control strategy online, which assures that the tracking error are semi-globally uniformly bounded. After that, the fixed-time disturbance observer that is constructed to provide the estimations of uncertainty including external disturbance leads to a more practical and robust flight control system for AHV-VGI. The uniform stability of the whole system is proved under the framework of Lyapunov theory. Finally, simulation results and analysis are presented to demonstrate the effectiveness of the proposed composite control scheme.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-26T03:21:24Z
      DOI: 10.1177/09544100221086051
       
  • Dynamic manipulability measure for on-orbit manipulation by frictional
           contacts

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      Authors: Li Chen, Zixuan Zheng, Jianping Yuan
      First page: 3457
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Due to unilateral constraints of frictional contacts and the dynamic coupling phenomenon, the study on the unfixed manipulation through frictional contacts for multi-arm space robots is few carried out. This paper proposes a new measure method to assess the dynamic manipulability of the unfixed manipulation through frictional contacts. In particular, the explicit map from the base actuation and joint torques to the object acceleration, the base acceleration, and the internal force is formulated under unilateral constraints of frictional contacts. Considering typical control scenarios of both free-floating and free-flying systems, dynamic manipulabilities are derived separately. As an illustrative example, the dynamic manipulability of a planar dual-arm space robot is computed and reported, which visualizes the influence of different system parameters.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-24T04:25:30Z
      DOI: 10.1177/09544100221086588
       
  • Mean value-based collaborative method for structural optimization of
           aircraft family

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      Authors: Xu Chao, Yao Weixing
      First page: 3468
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to improve the efficiency of the general platform optimization, a new mean value-based collaborative method (MVCM) for structural optimization of general platform is proposed. The key idea of this method is to decompose the general platform optimization problem into a system-level optimization problem and several independent subsystem-level optimization problems by introducing coordination variables. While meeting the design requirements and performance requirements, the subsystem optimizes each aircraft so that the design variables of each aircraft are as close as possible to coordination variables. The system-level coordination adjusts the coordination variables according to the results of each subsystem. With the continuous iteration between the system and the subsystems, the coordination variables that can maximize the generality of the product family are finally found. The numerical test results show that the MVCM can greatly improve the efficiency of the general platform optimization.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-12T11:07:39Z
      DOI: 10.1177/09544100221086324
       
  • Performance analysis and optimization of a radiating fin array

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      Authors: Kübra Solak, Cihat Arslantürk
      First page: 3482
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Space radiators are used to reject waste heat from power units, electronic devices, and various equipment in space vehicles. It is important that radiators can achieve the heat desired to be dissipated into space with the least mass. With a view to ensuring this aim, the heat transfer calculations that must be performed must be highly accurate. Therefore, the variation of conductivity with temperature should also be taken into account in the mathematical model. This paper presents heat transfer performance and optimization of a fin array consisting of straight fins put axially on a tube and radiating heat into deep space. The mathematical model yields the governing equation as a highly nonlinear integro-differential equation which is solved by the variation of parameters method (VPM). By applying an appropriate optimization procedure, the conduction–radiation parameter, Nc, providing maximum heat transfer is obtained for a given fixed fin profile emissivity, ε, opening angle among the fins, γ, and thermal conductivity parameter describing the variation of thermal conductivity, β. For the range of suitable problem parameters, optimum values of the dimensionless conduction–radiation parameter Nc, which is a combination of thermal and geometric quantities, are expressed in ε and γ for a given β. The correlation equations are expected to provide remarkable benefits to the designer.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-27T09:49:31Z
      DOI: 10.1177/09544100221088362
       
  • Maneuvering penetration strategies of ballistic missiles based on deep
           reinforcement learning

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      Authors: Xiaoqi Qiu, Changsheng Gao, Wuxing Jing
      First page: 3494
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In this paper, a ballistic missile terminal penetration scenario is studied, which contains three participants: target, missile, and defender. The ballistic missile attempts to hit the target while evading the defender. A maneuvering penetration guidance strategy that balances both the guidance accuracy and penetration capability is proposed through deep reinforcement learning. Reward shaping and random initialization are applied to improve training speed and generalization, respectively. The proposed strategy is developed based on the twin delayed deep deterministic policy gradient algorithm. It directly maps observations to actions and is an end-to-end guidance scheme that does not require an accurate model. The simulation results show that the proposed strategy has higher penetration probabilities than conventional strategies for different initial heading errors and even for defenders with different guidance laws, which indicates its good robustness and generalization. For different initial heading errors, it has learned different maneuvering modes and has certain intelligence. In addition, it is computationally small, does not consume much memory, and can be easily applied on modern flight computers.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-28T05:53:23Z
      DOI: 10.1177/09544100221088361
       
  • Research on aero-engine performance seeking control based on the NN-PSM
           on-board model

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      Authors: Qiangang Zheng, Dewei Xiang, Cheng Chen, Haibo Zhang
      First page: 3505
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      In order to improve the real-time performance of performance seeking control (PSC), a neural network-propulsion system matrix(NN-PSM) on-board model is proposed and applied to PSC. First, based on NN-PSM, a large-envelope, multi-variable on-board adaptive model is established. The PSM is extracted through a small deviation linearization method. The neural network is used to map the relationship between the flight conditions, engine control parameters, and the engine performance parameters, and designed a Kalman filter to estimate engine health parameters in real-time. Then, four PSC mode of maximum thrust, minimum fuel consumption, minimum high-pressure turbine inlet temperature, and minimum infrared radiation intensity are designed using LP optimization algorithm as optimize algorithm. Finally, the simulation results show that NN-PSM has much higher precision than Compact Propulsion System Model (CPSM). The PSC simulations show that compared with the PSC based on the conventional CPSM, the proposed method has much better real-time performance and get better engine performance, such as more thrust, less specific fuel consumption, and less turbine inlet temperature.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-17T07:55:34Z
      DOI: 10.1177/09544100221088360
       
  • Effects of confinement and curvature on a jet in a supersonic cross-flow

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      Authors: Dapeng Xiong, Mingbo Sun, Jiangfei Yu, Zhiwei Hu, Yixin Yang, Hongbo Wang, Zhengguo Wang
      First page: 3518
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      To reveal the effects of confinement and curvature on the jet mixing in a supersonic cross-flow, large eddy simulations were conducted to study the jet in supersonic cross-flow in a channel and a pipe at a Mach number of 2.7. The comparison was based on an equal friction Mach number, friction Reynolds number, and Prandtl number. The synthetic eddy model was utilized to generate the inflow turbulent boundary layer. Our study shows the major counter-rotating vortex pair (CVP) was higher in the pipe than in the channel, while the trailing CVP was larger and appeared within the recirculating flow. The pipe had a stronger shock train than the channel due to the confinement and curvature of the pipe. The jet penetration of the pipe is 18.4% larger than that of the channel at x/D = 10, and the stream velocity of the pipe is much more reduced behind the jet than in the channel. Three reasons for the higher mixing efficiency of the pipe are revealed according to our findings, including the larger and higher major CVP, the higher penetration, the stronger shock. The mixing efficiency of the pipe is 4.68% higher than that of the channel due to the above reasons at x/D = 10.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-18T10:10:08Z
      DOI: 10.1177/09544100221089067
       
  • Obstruction of infrared signature with cold gases

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      Authors: Onur Bas
      First page: 3531
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      The idea of infrared signature reduction by injecting cold gas between the source and observer has been investigated. Statistical narrow band coefficients of ethylene have been generated from HITRAN spectroscopic database and proposed to attenuate radiation on the 8–14 μm spectral region whereas CO2 is employed for 3–5 μm wavelength band suppression. Dilution of ethylene with CO2 also suppresses the flammability and guarantees safe operation. Several 1-D test cases are solved to validate the developed solver, and the proposed method is tested on 1-D and 3-D problems. The results satisfactorily show that a significant and safe radiance reduction can be achieved with cold CO2 diluted ethylene injection between the exhaust and observer on the whole spectrum.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-04-26T10:59:36Z
      DOI: 10.1177/09544100221089054
       
  • Robust attitude estimation for an unmanned aerial vehicle using multiple
           GPS receivers

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      Authors: Djamel DHAHBANE, Abdelkrim NEMRA, Samir SAKHI
      First page: 3540
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Estimation of the system state is an important task in the field of control, localization, and navigation. Many sensors are used to extract the attitude information. GPS (Global Positioning System) is widely used to provide position and velocity for ground and aerial vehicles. However, only a few research works have addressed the problem of attitude estimation using multiple GPS receivers. The main contribution of this paper consists on proposing a robust algorithm for attitude estimation of an unmanned aerial vehicle using INS/3GPS integration. First, we propose two alternative methods for attitude determination with three GPS receivers: Direct Computing Method (DCM) and Least Square Method (LSM) based on Singular Value Decomposition (SVD). Second, the attitude given by GPS receivers is fused with the measurement of a three-axis gyroscope using a robust Smooth Variable Structure Filter (SVSF). The optimal geometric configuration of GPS antennas is determined based on a deep performance analysis of the proposed system. Then, robustness analysis is assessed against measurement noise and parameters uncertainties. Simulation results are presented to demonstrate the robustness of the proposed approach. A more realistic evaluation of the proposed solution is obtained using an aerial vehicle type “Helicopter” from the Virtual Robot Experimentation Platform (VREP simulator). The proposed filter is compared with an Extended Kalman Filter (EKF). The obtained results have confirmed how much the SVSF is robust for attitude estimation in presence of the considered disturbances.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-06-03T08:03:34Z
      DOI: 10.1177/09544100221089220
       
  • Fixed time output feedback control for quadrotor unmanned aerial vehicle
           under disturbances

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      Authors: Shikai Shao, Shu Wang, Yuanjie Zhao
      First page: 3554
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      This paper designs a fixed time output feedback trajectory tracking control scheme for quadrotor Unmanned Aerial Vehicle with unmeasurable velocity and external disturbances. Firstly, a fixed time extend state observer (ESO) is devised to accurately observe the unknown velocity and estimate unknown total disturbances within a fixed time. Especially, the convergence time of system is independent of system initial states. Secondly, considering control accuracy and convergence rate, robust fixed time controllers are respectively designed for position and attitude system. Thirdly, the tracking errors of controller is capable of converging to zero according to homogeneous theory and Lyapunov theory, and superior results can be achieved under the proposed control scheme. Finally, simulations and comparison studies are verified to demonstrate the effectiveness of the designed fixed time output feedback control scheme.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-28T10:36:16Z
      DOI: 10.1177/09544100221089068
       
  • Vertical thrust-based effective flat-spin recovery of aircraft restricting
           altitude loss

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      Authors: Salahudden Salahudden, Ajoy K Ghosh
      First page: 3567
      Abstract: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, Ahead of Print.
      Among the various modes of aircraft spin, flat-spin being the most ruthless form, the severity and the flight parameters govern the recovery success rate. This paper presents a novel approach for utilizing vertical thrust to reduce the fatality of the flat-spin in terms of excessive altitude loss regulating the survivability post aircraft recovery. F-18 High Alpha Research Vehicle is considered for the present study to demonstrate effectiveness of the proposed method. The dynamics of vertical thrust add-on is conceptualized and incorporated to the standard aircraft. Subsequently, to validate the effectiveness of this mode of recovery as compared to the conventional primary control based method, standard sliding-mode control technique is adopted. Closed-loop simulation shows that vertical thrust restricts altitude loss and minimizes spin recovery time compared to the conventional mode of recovery from flat-spin. The outcome of the present study ensures the use of vertical thrust as a potential solution for minimizing aircraft flat-spin-related fatal accidents.
      Citation: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering
      PubDate: 2022-05-16T02:22:17Z
      DOI: 10.1177/09544100221089055
       
 
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