Journal Cover Aerospace Science and Technology
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   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1270-9638
   Published by Elsevier Homepage  [3177 journals]
  • Vibro-acoustic response and sound transmission loss characteristics of
           truss core sandwich panel filled with foam
    • Authors: M.P. Arunkumar; Jeyaraj Pitchaimani; K.V. Gangadharan; M.C. Leninbabu
      Pages: 1 - 11
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): M.P. Arunkumar, Jeyaraj Pitchaimani, K.V. Gangadharan, M.C. Leninbabu
      This paper presents the studies carried out for improving the acoustic behavior of truss core sandwich panel, which is mostly used in aerospace structural applications. The empty space of the truss core is filled with polyurethane foam (PUF) to achieve better vibro-acoustic and sound transmission loss characteristics. Initially equivalent elastic properties of the foam filled truss core sandwich panel are calculated. Then, the vibration response of the panel under a harmonic excitation is obtained based on the equivalent 2D finite element model. Finally, the vibration response is given as an input to the Rayleigh integral code built in-house to obtain the acoustic and sound transmission loss characteristics. The results revealed that PUF filling of the empty space of the truss core, significantly reduces resonant amplitudes of both vibration and acoustic responses. It is also observed that foam filling reduces the overall sound power level significantly. Similarly, sound transmission loss studies revealed that, sudden dips at resonance frequencies are significantly reduced. Also an experiment is conducted on forced vibration response of honeycomb core sandwich panel to show that equivalent 2D model can be used for predicting sound power level and transmission loss behavior.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.03.029
      Issue No: Vol. 78 (2018)
       
  • Optimization of rough transonic axial compressor
    • Authors: Zhihui Li; Yanming Liu
      Pages: 12 - 25
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Zhihui Li, Yanming Liu
      The influence of wall roughness on the performance of the axial transonic compressor stage was investigated with different values of roughness added to the blade, hub and shroud sections. The dimensionless sand-grain roughness model was used to capture the roughness effect and the results indicated that the increment of both end wall and blade surface roughness caused the deterioration of compressor stage performance. The sensitivity analysis method was used to distinguish which section mostly contributes to the whole performance degradation. Approximately a 95.31% degradation of the compressor peak efficiency came from the induced blade roughness, 3.58% from the hub surface roughness and only 1.08% from the casing surface. The present study also investigated how the optimized design of compressor blades was affected by considering a surface roughness effect representative of in-service use. Two optimization strategies were proposed to improve the compressor efficiency and total pressure ratio by changing the distributions of the blade angles along the chord. The first strategy considered the compressor surface to be hydraulically smooth and the consequent Pareto Front designs were degraded by increasing the level of surface roughness with the second approach considering the surface roughness from the outset of optimization. The optimization result showed that the degraded compressors from the first strategy was still among the best performing Pareto Front designs in terms of adiabatic efficiency and pressure ratio when compared to the second approach. This means that the roughness effect can be regarded as an additional factor and be considered in the end of the design process for single-stage compressors.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.03.031
      Issue No: Vol. 78 (2018)
       
  • Effect of dual-catalytic bed using two different catalyst sizes for
           hydrogen peroxide thruster
    • Authors: Seonuk Heo; Sungkwon Jo; Yongtae Yun; Sejin Kwon
      Pages: 26 - 32
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Seonuk Heo, Sungkwon Jo, Yongtae Yun, Sejin Kwon
      For a catalytic bed in hydrogen peroxide based propulsion systems, a high pressure drop can cause significant problems. Hence, a dual-catalytic bed was suggested to reduce the pressure drop across the catalytic bed. Catalysts of two different sizes (1/8 inch, and 1.18–2.00 mm) were employed, which were fabricated using an impregnation method with MnO2 and PbO as the active materials. The upstream and downstream sides of the dual-catalytic bed were loaded with the catalyst with dimensions of 1.18–2.00 mm and 1/8 inch, respectively. The effectiveness of the dual-catalytic bed was verified by conducting hot-fire tests with hydrogen peroxide monopropellant mode. The trends in the pressure drop across the catalytic bed and the characteristic velocity efficiency were investigated with respect to the mass flux and mass ratio of the loaded catalysts. As the mass ratio of the smaller catalyst was reduced to 18.3%, the pressure drop constantly decreased with an identical mass flux, though most of the fed hydrogen peroxide was still fully decomposed.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.03.032
      Issue No: Vol. 78 (2018)
       
  • Global stabilization of the linearized three-axis axisymmetric spacecraft
           attitude control system by bounded linear feedback
    • Authors: Weiwei Luo; Bin Zhou; Guang-Ren Duan
      Pages: 33 - 42
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Weiwei Luo, Bin Zhou, Guang-Ren Duan
      In this paper, the three-axis attitude stabilization of the axisymmetric spacecraft with bounded inputs is studied. By constructing some novel state transformations, saturated linear state feedback controllers are constructed for the considered attitude control system. By constructing suitable quadratic plus integral Lyapunov functions, globally asymptotic stability of the closed-loop systems is proved if the feedback gain parameters satisfy some explicit conditions. By solving some min–max optimization problems, a global optimal feedback gain for the underactuated attitude stabilization system is proposed such that the convergence rate of the linearized closed-loop system is maximized. Numerical simulations show the effectiveness of the proposed approaches.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.021
      Issue No: Vol. 78 (2018)
       
  • A dual-rate hybrid filtering method to eliminate high-order position
           errors of GPS in POS
    • Authors: Zhuangsheng Zhu; Chi Li; Wen Ye
      Pages: 43 - 53
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Zhuangsheng Zhu, Chi Li, Wen Ye
      The Position and Orientation System (POS) serves as a key component for the airborne remote sensing system, which integrates Strapdown Inertial Navigation System (SINS) and Global Position System (GPS) to provide the reliable and continuous motion compensation using Kalman Filter (KF). However, the high-order position errors resulting from C/A (Coarse/Acquisition) Code GPS cannot be effectively compensated or estimated by the traditional KF, which severely weakens the imaging quality. In this paper, we propose a Dual-rate Hybrid Filter (DHF) to deal with the high-order position errors based on Least Squares Support Vector Machine (LSSVM) and Kalman Filter. DHF builds a low update rate filter by integrating high-precision SINS and online LSSVM to isolate the high-order position errors. Meanwhile, the high update rate filter of DHF maintains the advantages of traditional SINS/GPS integrated navigation system to restrain the accumulation errors of system. The experimental results show that the proposed method significantly reduces the high-order position errors by 84.6% at each sampling period comparing with the conventional single KF based SINS/GPS integrated navigation system.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.03.036
      Issue No: Vol. 78 (2018)
       
  • A new sliding mode control design for integrated missile guidance and
           control system
    • Authors: Jianguo Guo; Yu Xiong; Jun Zhou
      Pages: 54 - 61
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Jianguo Guo, Yu Xiong, Jun Zhou
      A new sliding mode control algorithm for integrated guidance and control (IGC) system is proposed in this paper. Firstly, the IGC model is established and the nonlinearities, target maneuvers, perturbations caused by variations of aerodynamic parameters, etc. are viewed as disturbance, so that the IGC system becomes a mismatched uncertain linear system. Secondly, a second-order disturbance observer is used to estimate the disturbances and their derivatives. Thirdly, an integral sliding mode surface is designed to obtain the rudder deflection command directly instead of the back-stepping control (BC) algorithm used in conventional IGC system, which achieves the real sense of IGC, and the stability of the system is proven strictly by Lyapunov stability theory. Finally, the superiority of the proposed IGC method is verified by comparing the simulation results of different methods under different cases.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.03.042
      Issue No: Vol. 78 (2018)
       
  • Pendulum maneuvering strategy for hypersonic glide vehicles
    • Authors: Jianwen Zhu; Ruizhi He; Guojian Tang; Weimin Bao
      Pages: 62 - 70
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Jianwen Zhu, Ruizhi He, Guojian Tang, Weimin Bao
      In order to improve the penetration performance of hypersonic glide vehicles, a lateral pendulum maneuvering strategy is proposed. A single radar trajectory tracking model is established and EKF is used to estimate the entire trajectory parameters. Based on the analysis of the composition of the defense system and the intercepting mechanism, the pendulum maneuvering trajectory is designed, and the influencing factors of the gliding penetration performance are analyzed. Then, an integrated index of penetration performance consists of the hit point prediction error, intercepting velocity, overload and the energy consumption caused by maneuver is constructed. Furthermore, a maneuvering strategy is proposed that the first maneuver is performed to enlarge prediction error of hitting point when the vehicle entrances the radar coverage, and the second one is carried out in the intercept zone to increase the maneuvering overload. The two maneuvers are the combat of the glider to the early warning system and the intercept system respectively, which can effectively enhance the penetration performance with less energy consumption.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.03.038
      Issue No: Vol. 78 (2018)
       
  • Assessment of low-fidelity fluid–structure interaction model for
           flexible propeller blades
    • Authors: Jurij Sodja; Roeland De Breuker; Dejan Nozak; Radovan Drazumeric; Pier Marzocca
      Pages: 71 - 88
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Jurij Sodja, Roeland De Breuker, Dejan Nozak, Radovan Drazumeric, Pier Marzocca
      Low-fidelity fluid–structure interaction model of flexible propeller blades is assessed by means of comparison with high-fidelity aeroelastic results. The low-fidelity model is based on a coupled extended blade-element momentum model and non-linear beam theory which were both implemented in Matlab. High-fidelity fluid–structure interaction analysis is based on coupling commercial computational fluid dynamics and computational structural dynamics codes. For this purpose, Ansys CFX® and Ansys Mechanical® were used. Three different flexible propeller blade geometries are considered in this study: straight, backward swept, and forward swept. The specific backward and forward swept blades are chosen due to their aeroelastic response and its influence on the propulsive performance of the blade while a straight blade was selected in order to serve as a reference. First, the high-fidelity method is validated against experimental data available for the selected blade geometries. Then the high- and low-fidelity methods are compared in terms of integral thrust and breaking power as well as their respective distributions along the blades are compared for different advancing ratios. In a structural sense, the comparison is performed by analyzing the blade bending and torsional deformation. Based on the obtained results, given the simplicity of the low-fidelity method, it can be concluded that the agreement between the two methods is reasonably good. Moreover, an important result of the comparison study is an observation that the advance ratio is no longer a valid measure of similarity in the case of flexible propeller blades and the behavior of such blades can change significantly with changing operating conditions while keeping the advance ratio constant. This observation is supported by both high- and low-fidelity methods.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.03.044
      Issue No: Vol. 78 (2018)
       
  • Influence of Mach number and angle of attack on the two-dimensional
           transonic buffet phenomenon
    • Authors: Nicholas F. Giannelis; Oleg Levinski; Gareth A. Vio
      Pages: 89 - 101
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Nicholas F. Giannelis, Oleg Levinski, Gareth A. Vio
      Within a narrow band of flight conditions in the transonic regime, self-sustained shock oscillations that involve the interaction between shock-waves and intermittently separated shear layers may develop. This phenomenon, known as transonic shock buffet, limits the flight envelope and is detrimental to both aircraft handling quality and structural integrity. In this investigation, numerical simulation of transonic shock buffet over the OAT15A aerofoil is performed to explore the buffet envelope. Unsteady Reynolds-Averaged Navier–Stokes simulations are validated against available experimental data to ascertain the most effective combination of simulation parameters to reproduce autonomous shock oscillations. From the baseline test case, the influence of Mach number and angle of attack on the nature of the buffet response is investigated. Radial Basis Function surrogate models are developed to represent the variation of buffet amplitude and frequency with flight condition. While the frequency is found to increase monotonically with both parameters, variation in buffet amplitude through the region of shock unsteadiness is more complex, particularly at high angles of attack. This is related to a bifurcation in the behaviour of the shock. As incidence increases from onset, the shock dynamics transition from periodic oscillations over the suction surface to quasi-periodic motions, whereby the shock is propelled forward into the oncoming flow during its upstream excursion.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.03.045
      Issue No: Vol. 78 (2018)
       
  • Attitude tracking control for a space moving target with high dynamic
           performance using hybrid actuator
    • Authors: Yun-Hua Wu; Feng Han; Mo-Hong Zheng; Feng Wang; Bing Hua; Zhi-Ming Chen; Yue-Hua Cheng
      Pages: 102 - 117
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Yun-Hua Wu, Feng Han, Mo-Hong Zheng, Feng Wang, Bing Hua, Zhi-Ming Chen, Yue-Hua Cheng
      Attitude tracking control for a space moving target (such as debris or malfunctioning satellite) is investigated in this paper, which is different from the traditional agile attitude maneuvering and tracking control, and is a challenging problem for attitude control system, requiring agility, large control torque output, and high dynamic accuracy, etc. The rapidly moving target and spacecraft pose several tough issues such as agile attitude tracking control and actuator configuration design. A novel attitude tracking strategy is proposed to tackle the dynamic imaging process, including three phases, earth observation, attitude adjustment and dynamic tracking phase. With the accomplishment of attitude adjustment, the spacecraft will point toward the target to start the imaging task. For the maneuvers in the attitude adjustment and tracking phases, a combined control strategy consisting of saturation controller and backstepping controller is proposed. The former one constrains the attitude angular velocity as well as the required momentum on the actuators during the initial phase, while the backstepping controller guarantees the control accuracy with high dynamic performance in the imaging phase. A hybrid momentum exchanging actuator consisting of Control Moment Gyro (CMG) and Reaction Wheel (RW) is introduced to satisfy the great control torque demand. Null motion strategy is derived for the hybrid actuator to deal with CMG singularity and RW saturation simultaneously. Numerical simulations have demonstrated the advantages of the hybrid actuator and the proposed attitude control strategy, which not only enables the spacecraft to maneuver rapidly but also guarantees the tracking accuracy.

      PubDate: 2018-04-23T15:32:25Z
      DOI: 10.1016/j.ast.2018.03.041
      Issue No: Vol. 78 (2018)
       
  • Numerical study on the nonlinear resonant dynamics of carbon
           nanotube/fiber/polymer multiscale laminated composite rectangular plates
           with various boundary conditions
    • Authors: Raheb Gholami; Reza Ansari; Yousef Gholami
      Pages: 118 - 129
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Raheb Gholami, Reza Ansari, Yousef Gholami
      This work deals with the numerical investigation of the geometrically nonlinear resonant dynamics of carbon nanotube/fiber/polymer multiscale laminated composite (CNT-FPMLC) rectangular plates with different boundary conditions. It is assumed that a uniform distributed harmonic excitation load in the transverse direction is applied to the CNT-FPMLC plates. The material properties of multiscale composite are estimated by means of the fiber micromechanics and Halpin–Tsai relations. Furthermore, it is assumed that the carbon nanotubes (CNTs) are distributed uniformly and oriented arbitrarily through the epoxy resin matrix. Based upon the Mindlin plate theory and using the von Kármán hypotheses, the governing equations of motion for the in-plane and out-of-plane motions including the effects of geometric nonlinearity, rotary inertia and shear deformation are achieved by means of the Hamilton's principle. In the solution process, the nonlinear partial differential equations of motions and associated boundary conditions are discretized via the generalized differential quadrature (GDQ) and afterward converted into a Duffing-type nonlinear time-varying set of ordinary differential equations via a numerical Galerkin approach. Then, the time periodic discretization method and the pseudo-arc length continuation technique are employed to solve the obtained equations in order to achieve the frequency–response curves associated with nonlinear free and forced resonances for the CNT-FPMLC rectangular plates with various edge supports. Finally, the influences of important design parameters including the weight percentage of single-walled and multi-walled CNTs, volume fraction of fibers, CNT aspect ratio, plate geometry and boundary conditions on the nonlinear resonant dynamics and linear natural frequencies of CNT-FPMLC rectangular plate are investigated in the numerical results.

      PubDate: 2018-04-23T15:32:25Z
      DOI: 10.1016/j.ast.2018.03.043
      Issue No: Vol. 78 (2018)
       
  • Morphing and growing micro unmanned air vehicle: Sizing process and
           stability
    • Authors: M. Hassanalian; A. Quintana; A. Abdelkefi
      Pages: 130 - 146
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): M. Hassanalian, A. Quintana, A. Abdelkefi
      An optimized and comprehensive method is proposed in order to design an efficient micro unmanned air vehicle with morphing and growing capabilities. In the sizing process, to select the optimum wing shape, three different shapes are compared based on an aerodynamic analysis, and a tapered wing is selected for the compressed mode. Then, since the wingspan, wing area, wing loading, and other parameters are changing as function of time, a transition analysis is carried-out during the sizing process. By using the calculated surface area and considered aspect ratio for compression and expansion modes, the wingspan is determined as function of time. Considering the estimated weight, the required lift coefficient is calculated and then two types of airfoils are selected. Finally, after completing the optimal geometric design, aerodynamic analyses are carried out to investigate the performance of the growing drone. The proposed strategy for designing efficient micro unmanned air vehicles for a well-defined mission can be utilized and extended to design other growing micro unmanned systems depending on the mission.

      PubDate: 2018-04-23T15:32:25Z
      DOI: 10.1016/j.ast.2018.04.020
      Issue No: Vol. 78 (2018)
       
  • Effect of cavity fueling schemes on the laser-induced plasma ignition
           process in a scramjet combustor
    • Authors: Zun Cai; Jiajian Zhu; Mingbo Sun; Zhenguo Wang
      Pages: 197 - 204
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Zun Cai, Jiajian Zhu, Mingbo Sun, Zhenguo Wang
      Laser-induced plasma (LIP) ignition processes in a cavity-based scramjet combustor were investigated experimentally in this study. CH⁎ spontaneous emission recorded at a flame rate of 50 kHz was used to characterize the ignition and flame stabilization processes. Numerical calculation was also performed to characterize the non-reacting flow-field structures. Effect of cavity fueling schemes on the LIP ignition process in the rear-wall-expansion cavity was then examined. It is found that the cavity fueling scheme acts as a dominant factor in a LIP ignition process. After a LIP ignition in the cavity rearward, the initial flame kernel is likely to anchor and grow directly in the rearward of the cavity under cavity upstream fueling schemes. However, the flame kernel will propagate towards the cavity leading edge and grow there under cavity direct fueling schemes. It is concluded that both chemical and turbulent issues of the flow-field affect the LIP ignition process. Local fuel-rich environment inside the cavity is favorable for a LIP ignition process, and the fueling scheme with parallel fuel injectors upstream the cavity is most favorable for a LIP ignition which presents a stable combustion process.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.016
      Issue No: Vol. 78 (2018)
       
  • Reentry guidance with constrained impact for hypersonic weapon by novel
           particle swarm optimization
    • Authors: Hongyu Zhou; Xiaogang Wang; Bing Bai; Naigang Cui
      Pages: 205 - 213
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Hongyu Zhou, Xiaogang Wang, Bing Bai, Naigang Cui
      The novel reentry guidance law is proposed for hypersonic weapons to strike a stationary ground target at a constrained impact angle. This guidance law is based on proportional navigation guidance (PNG) whose gain is set as the function of range-to-go. To be resistant to disturbances and adaptive to various missions, the gain is refreshed in every guidance cycle. To lessen the control effort, the gain is optimized by a novel particle swarm optimization (NPSO) algorithm. NPSO needs a small number of particles for it can convert infeasible particles into feasible ones. Moreover, a mutation mechanism is introduced to accelerate convergence. In addition, there is only one single terminal constraint, that is, the impact angle in the optimization problem, because the terminal position is automatically identified using PNG. Compared with existing guidance laws, the proposed one needs neither complex derivation nor prior assumption. It also takes into consideration the constraints in lateral acceleration and look angle, which are often neglected in PNG-based laws. The adaptability under different scenarios, the robustness under disturbances and the potential for online application are demonstrated by simulation results. Numerical examples also show the superiority of NPSO when compared with the GPOPS.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.024
      Issue No: Vol. 78 (2018)
       
  • Gas kinetic scheme for turbulence simulation
    • Authors: Shuang Tan; Qibing Li; Zhixiang Xiao; Song Fu
      Pages: 214 - 227
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Shuang Tan, Qibing Li, Zhixiang Xiao, Song Fu
      The extended gas-kinetic scheme (GKS) for turbulence simulations is developed based on the generalized BGK equation with the effective relaxation time. This relaxation time can be computed from the turbulent viscosity, through which turbulence models can be directly combined. For engineering low-cost simulations of high Reynolds number flows, common-used RANS models are applied, while the LES and hybrid RANS/LES (DES and IDDES) models as well as the minimized dispersion and controllable dissipation (MDCD) reconstruction are adopted in high fidelity turbulence simulations. In addition, the turbulent transport equations are solved in a strongly coupled way by using GKS with scalar transport. The extended GKS is applied in typical turbulent flow predictions including the RANS simulation of hypersonic compression ramp flow and the detailed simulation of multiscale turbulent structures in low-speed cylinder flow with hybrid models. The predicted results agree well with existing experimental measurements and numerical studies, which shows the good accuracy, resolution and robustness of the extended GKS and reveals the wide prospects in turbulence simulations on different model scales, including the multiscale models such as hybrid RANS/LES methods. Furthermore, the multiscale turbulence simulation methods are worthy of further studies based on the generalized BGK model.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.022
      Issue No: Vol. 78 (2018)
       
  • Adaptive attitude tracking control for hypersonic reentry vehicles via
           sliding mode-based coupling effect-triggered approach
    • Authors: Zongyi Guo; Jianguo Guo; Jun Zhou
      Pages: 228 - 240
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Zongyi Guo, Jianguo Guo, Jun Zhou
      This paper proposed a coupling effect-triggered control approach for hypersonic reentry vehicles attitude tracking system based on the adaptive sliding mode techniques. A coupling effect indicator (CEI), which is established based on the Lyapunov stability theory, is obtained to demonstrate whether a coupling harms or benefits the system. In consequence, the coupling effect-triggered control driven by the CEI is developed to cancel the harmful couplings while keeping the beneficial couplings. Meanwhile, the robustness of the proposed method is enhanced by the adaptive sliding mode approach even when the boundary of the disturbance is unknown. To avoid the non-differentiable terms in the controller design, the command filtered scheme is introduced and the bounded stability of the closed-loop system is guaranteed. This technique outperforms the existing controllers which do not consider the coupling effect in the transient response. Finally, application to the hypersonic vehicle system is presented to demonstrate the validity of the proposed control scheme.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.017
      Issue No: Vol. 78 (2018)
       
  • An improved geometric parameter airfoil parameterization method
    • Authors: Xiaoqiang Lu; Jun Huang; Lei Song; Jing Li
      Pages: 241 - 247
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Xiaoqiang Lu, Jun Huang, Lei Song, Jing Li
      In the process of airfoil optimization, it is required to represent an airfoil with parameters, and the goal is to represent arbitrary airfoils with less parameters. In this paper, a new airfoil parameterization method is proposed, called the IGP method, which realized camber-thickness decoupling so that camber and thickness could be constructed respectively with fewer parameters compared to the previous methods. Also the IGP method is featured with clear physical meaning and consecution of parameter domain. The mathematical model is introduced. With this camber-thickness decoupling method, the definition and the domain of the control parameters was determined. To validate the feasibility, the most used airfoils were fitted and reconstructed by this method. Then according to the results of geometric and aerodynamic comparative analysis between original airfoils and fitted airfoils, the precision of the IGP method could meet the requirement of airfoil optimization.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.025
      Issue No: Vol. 78 (2018)
       
  • Multi-objective multidisciplinary design analyses and optimization of high
           altitude airships
    • Authors: Mohammad Irfan Alam; Rajkumar S. Pant
      Pages: 248 - 259
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Mohammad Irfan Alam, Rajkumar S. Pant
      High Altitude Airships (HAAs) offer tremendous potential as long-endurance relocatable aerial platforms for several strategic and commercial applications. Design, analyses, and optimization of HAAs involves a complex interplay of various disciplines, and hence a multidisciplinary approach is essential. This paper describes a methodology to obtain the optimal design of an HAA meeting the requirements of onboard payload and power. The methodology couples six mutually interacting disciplines, viz., Environment, Geometry, Energy, Structure, Aerodynamics, and Thermal. The design problem is posed in a multidisciplinary optimization framework involving eleven design variables drawn from these six disciplines, and optimal solutions are obtained using Genetic Algorithm. The methodology obtains the optimal envelope shape, layout of the solar array, and altitude of operation, and determines the most critical day of operation. To demonstrate the efficacy of methodology, the optimal solutions are obtained for five different geographical locations of deployment, and compared with those for a standard envelope shape. A comparative study of these solutions is carried out to highlight the importance of thermal considerations in design optimization. Since the problem involves mutually conflicting disciplines; a multi-objective optimization involving Aerodynamics and Structures are also carried out. It is noticed that operating parameters and thermal behavior have a significant effect on design.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.028
      Issue No: Vol. 78 (2018)
       
  • Smart control and vibration of viscoelastic actuator-multiphase
           nanocomposite conical shells-sensor considering hygrothermal load based on
           layerwise theory
    • Authors: Mohammad Hadi Hajmohammad; Ahmad Farrokhian; Reza Kolahchi
      Pages: 260 - 270
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Mohammad Hadi Hajmohammad, Ahmad Farrokhian, Reza Kolahchi
      Smart control and vibration analysis of laminated sandwich truncated conical shells with piezoelectric layers as sensor and actuator are presented in this paper. The core of the sandwich structure is reinforced by carbon fibers and carbon nanotubes (CNTs) where the effective material properties are obtained by Halpin–Tsai model. The actuator layer is subjected to external voltage and a Proportional-Derivative (PD) controller is used for sensor output control. Based on Kelvin–Voigt model, the structural damping effects are assumed. The formulation of the problem is based on the layerwise first order shear deformation theory (FSDT). Considering the continuity of the displacements and the internal stress fields at the interfaces of the layers, the motion equations are derived utilizing Hamilton's principle. The solution of the problem is carried out by differential quadrature method (DQM) for calculating the frequency of the smart sandwich structure. The effects of different parameters such as structural damping, weight percent of CNTs, boundary conditions, geometrical parameters of the structure, semi vertex angle of the cone, external voltage, temperature and moisture changes are examined on the vibration response of the smart sandwich structure. Numerical results indicate that using a PD controller can increase the frequency of the structure. In addition, the hygrothermal load decreases the vibration frequency of the system.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.030
      Issue No: Vol. 78 (2018)
       
  • Three-dimensional through-flow modelling of axial flow compressor rotating
           stall and surge
    • Authors: Mauro Righi; Vassilios Pachidis; László Könözsy; Lucas Pawsey
      Pages: 271 - 279
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Mauro Righi, Vassilios Pachidis, László Könözsy, Lucas Pawsey
      This paper presents a three-dimensional through-flow approach based on the cylindrical Euler equations incorporating a body force method. Blade performance is captured through a mixture of empirical correlations and a novel reverse flow treatment. The code is the first application of a physically correct Godunov solver to three-dimensional rotating stall and surge modelling. This solver ensures the accurate calculation of inter-cell fluxes unlike in typical modern CFD codes in which the non-linear convective terms are linearised. Validation consists of modelling a low speed three-stage axial compressor in all operating regions, recreating the reverse flow, rotating stall and forward flow characteristics with good agreement to experimental data. Additional comparisons are made against rotating stall cell size and speed, to which good agreement is also shown. The paper ends with some full surge cycle simulations modifying both the tank volume after the compressor and the level of inlet distortion applied. Both tank volume and level of distortion have been found to affect the type of instability developed. The development of this code is a step forward in compressor rotating stall and reverse flow modelling and allows recreation of a full compressor map at a significantly low computational cost when compared to commercially available 3D CFD codes.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.021
      Issue No: Vol. 78 (2018)
       
  • Reduction of power consumption on quadrotor vehicles via trajectory design
           and a controller-gains tuning stage
    • Authors: Roger Miranda-Colorado; Luis T. Aguilar; José E. Herrero-Brito
      Pages: 280 - 296
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Roger Miranda-Colorado, Luis T. Aguilar, José E. Herrero-Brito
      This work presents a methodology for reducing power consumption on quadrotor vehicles. The proposed methodology combines both, a trajectory design procedure and a controller-gains tuning stage. The quadrotor is operated in closed-loop by means of a terminal sliding modes controller, whose stability analysis is provided by using a strict Lyapunov function. The trajectory design stage allows designing an optimal trajectory with smooth transitions by minimizing a criterion function using dynamic optimization theory. Furthermore, in order to reduce power consumption, a performance index depending on the tracking error and the quadrotor inputs is used on a control-gains tuning stage based on a nature inspired evolutionary meta-heuristic algorithm, namely the cuckoo search algorithm. The quadrotor terminal sliding modes controller is compared to another sliding mode control algorithm, and the performance of each controller is assessed by considering aero-dynamical disturbances and parametric uncertainties. Numerical simulations show that the tracking error and power consumption are reduced when the trajectory tracking and controller-gains tuning stages are used. Besides, it is shown that the proposed terminal sliding modes controller outperforms a conventional sliding mode control scheme.

      PubDate: 2018-04-30T15:45:37Z
      DOI: 10.1016/j.ast.2018.04.027
      Issue No: Vol. 78 (2018)
       
  • Characteristics of unsteady total pressure distortion for a complex
           aero-engine intake duct
    • Authors: Geoffrey Tanguy; David G. MacManus; Eric Garnier; Peter G. Martin
      Pages: 297 - 311
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Geoffrey Tanguy, David G. MacManus, Eric Garnier, Peter G. Martin
      Some types of aero-engine intake systems are susceptible to the generation of secondary flows with high levels of total pressure fluctuations. The resulting peak distortion events may exceed the tolerance level of a given engine, leading to handling problems or to compressor surge. Previous work used distortion descriptors for the assessment of intake-engine compatibility to characterise modestly curved intakes where most of the self-generated time-dependent distortion was typically found to be dominated by stochastic events. This work investigates the time-dependent total pressure distortion at the exit of two high off-set diffusing S-duct intakes with the aim of establishing whether this classical approach, or similar, could be applied in these instances. The assessment of joint probability maps for time dependent radial and circumferential distortion metrics demonstrated that local ring-based distortion descriptors are more appropriate to characterise peak events. Extreme Value Theory (EVT) was applied to predict the peak distortion levels that could occur for a test time beyond the experimental data set available. Systematic assessments of model sensitivities to the de-clustering frequency, the number of exceedances and sample time length were used to extend the EVT application to local distortion descriptors and to provide guidelines on its usage.

      PubDate: 2018-05-10T11:13:17Z
      DOI: 10.1016/j.ast.2018.04.031
      Issue No: Vol. 78 (2018)
       
  • Method for simulating the performance of a boundary layer ingesting
           propulsion system at design and off-design
    • Authors: C. Goldberg; D. Nalianda; D. MacManus; P. Pilidis; J. Felder
      Pages: 312 - 319
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): C. Goldberg, D. Nalianda, D. MacManus, P. Pilidis, J. Felder
      Boundary layer ingestion has emerged as a potential propulsion concept on novel aircraft configurations for the future. As these concepts progress, preliminary design tools are required that enable the simulation of these aircraft and the rapid analysis of multiple configurations. Simulation tools for boundary layer ingesting propulsion systems tend to focus on proving performance benefits at design point. However, the simulation of aircraft configurations that utilise boundary layer ingestion requires a method to simulate the propulsion system at a range of flight conditions other than design point. A tool is therefore required to enable simulations at off-design. This research presents a work flow to simulate a boundary layer ingesting propulsion system at design and off-design. The process is intended as a tool for design space exploration and the rapid analysis of concepts at the conceptualisation phase. Boundary layer calculations have been combined with conventional 1-D gas turbine performance methods to predict performance of a propulsion system at design point. This method is then extended to enable simulations at off-design conditions for a range of flight conditions or propulsion system power settings. The formulation provides a thrust-drag representation that supports conventional aircraft simulation tools. A case study of an aircraft configuration which utilises an array of boundary layer ingesting propulsors is used to demonstrate the process. The performance of individual propulsors in the array is compared at off-design. Simulations found that, although each propulsor was sized for the same propulsive force at design point, off-design performance diverged depending on operating conditions. In addition, the performance of the propulsor array as a whole was predicted as a function of altitude and Mach number. The case study is used to draw general conclusions on the performance characteristics of a boundary layer ingesting propulsor.

      PubDate: 2018-05-10T11:13:17Z
      DOI: 10.1016/j.ast.2018.04.026
      Issue No: Vol. 78 (2018)
       
  • Flow control mechanisms of a combined approach using blade slot and vortex
           generator in compressor cascade
    • Authors: Jiaguo Hu; Rugen Wang; Danqin Huang
      Pages: 320 - 331
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Jiaguo Hu, Rugen Wang, Danqin Huang
      Experiments proved the performance gains in a high-load cascade using a new combined flow control approach, but lack of clear explanations on flow interactions between the configurations and the cascade flow. A detailed discussion is conducted here to further reveal the flow control mechanisms based on experimental and numerical results. An overview of experimental studies is firstly presented to conclude the flow control benefits and to put forward the questions for the simulations. Cascade flow fields observed by experiments show that the combined approach works by two aspects: the slot produces high-speed jets to re-energize the suction side separated flows and reattach them to the suction surface; the vortex generator (VG) creates a counter-rotating vortex into cascade passage to further reduce the end-wall cross flows. Thus, both the two main sources of separations in cascade flow are considerably suppressed. The corner separation is suppressed by delaying the passage vortex ( P V ): The VG counter-balances and deflects the P V while the slot jet further limits its pitch-wise width. Coupling the effects of two devices, the cascade flow structure is improved and main vortices are significantly reduced in size and intensity, result in greater separation control effects than the individuals in the high-load cascade.

      PubDate: 2018-05-10T11:13:17Z
      DOI: 10.1016/j.ast.2018.04.034
      Issue No: Vol. 78 (2018)
       
  • Robust fault-tolerant controller design for aerodynamic load simulator
    • Authors: Abdolah Shamisa; Zahra Kiani
      Pages: 332 - 341
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Abdolah Shamisa, Zahra Kiani
      Load simulator is one of the main mechanisms for stability and performance evaluation of the rotational/translational actuators in the laboratory. The movement of (under testing) actuator generates a large disturbance on the load simulator known as “extraneous torque”. Elimination of this large surplus disturbance is the main concern of the dynamic load simulator design. The faults are unavoidable events in system operation. Sensor or actuator faults frequently occur in flight systems. The design method based on Quantitative Feedback Theory (QFT) can be used as a passive Fault-Tolerant Control (FTC) of the plants with sensor or actuator faults. In this paper, a QFT-FTC is proposed for the electric load simulator (ELS) in presence of sensor and actuator faults. For this purpose, a particular type of faults is used, which the sensor and actuator faults are considered as semi-deterministic jumps that occurring at random intervals with random amplitudes. In the first step, the faults are converted to parameter uncertainties and disturbance is transferred to the input and output of the plant. Then, a QFT controller is designed for this uncertain plant. Proposed QFT-FTC attenuates the large disturbance even if the control effort is limited. Under these circumstances, an adequate bandwidth is achieved. Furthermore, semi-deterministic jumping faults on sensor and actuator are applied during the simulations and high robust tracking performance is obtained in presence of the saturated control. Compared to H-infinity Controller, the proposed controller has a simpler structure and its tracking performance is better than H-infinity method.

      PubDate: 2018-05-10T11:13:17Z
      DOI: 10.1016/j.ast.2018.04.035
      Issue No: Vol. 78 (2018)
       
  • Cable fracture simulation and experiment of a negative Gaussian curvature
           cable dome
    • Authors: Jiamin Guo; Guangen Zhou; Dai Zhou; Weigang Chen; ZhiXin Xiong; Shilin Dong
      Pages: 342 - 353
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Jiamin Guo, Guangen Zhou, Dai Zhou, Weigang Chen, ZhiXin Xiong, Shilin Dong
      This paper describes a newly developed negative Gaussian cable-strut structure. It focuses on the fracture of a member using an experimental model and the corresponding vector form intrinsic finite element (VFIFE) model. First, this study considered the VFIFE algorithm for bars, cables, and beams. Next, an experimental model of a negative Gaussian curvature cable dome with its supporting system and the corresponding VFIFE model were built. Then, the given ridge cable was fractured using a shear force, and the structural dynamic response during fracture was tested. Finally, to further study the influence of fracture on the structure, different sections of three main ridge cables were selected, and their fractures were successively simulated using the VFIFE model. The results indicated that the VFIFE was an efficient and accurate way to simulate the member fracture of a negative Gaussian curvature cable dome. Furthermore, the results confirmed that members in a section with a negative curvature not only have a much greater effect on the structure but also are much more sensitive to member fracture.

      PubDate: 2018-05-10T11:13:17Z
      DOI: 10.1016/j.ast.2018.04.033
      Issue No: Vol. 78 (2018)
       
  • Unsteady aerodynamic effects in landing operation of transport aircraft
           and controllability with fuzzy-logic dynamic inversion
    • Authors: C. Edward Lan; Ray C. Chang
      Pages: 354 - 363
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): C. Edward Lan, Ray C. Chang
      Aircraft landing in strong wind has been a safety problem for all types of aircraft. The specific issues involve hard landing, roll oscillation and runway veer-off. These issues are related to atmospheric disturbances, and/or dynamic ground effect. As a result, the aerodynamics will be different from those in steady flow concept. In this paper, some of the pertinent stability and control derivatives based on a small-disturbance concept will be presented. How these local stability and control characteristics affect global controllability will be examined with Fuzzy-Logic Dynamic Inversion. Controllability is judged from whether necessary control deflections exceed the imposed limits. Specific examples involving a twin-jet transport with hard landing, rolling oscillation before touchdown and runway veer-off event due to varying crosswind after touchdown are illustrated.

      PubDate: 2018-05-10T11:13:17Z
      DOI: 10.1016/j.ast.2018.04.032
      Issue No: Vol. 78 (2018)
       
  • Parametric study of supersonic film cooling in dual bell nozzle for an
           experimental air–kerosene engine
    • Authors: Siba Prasad Choudhury; Abhilash Suryan; J.C. Pisharady; A. Jayashree; Khalid Rashid
      Pages: 364 - 376
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Siba Prasad Choudhury, Abhilash Suryan, J.C. Pisharady, A. Jayashree, Khalid Rashid
      Numerical analysis is performed on a dual bell nozzle designed for an experimental semi-cryogenic rocket engine application to predict the effect of film injection on nozzle flow characteristics and transitional behavior. Both start-up and high-altitude operation regimes are simulated to predict actual flight conditions of a dual bell nozzle. Coolant is injected at two locations and at different operating conditions to study the effect of various parameters on flow behavior. Changes in shock interaction and shock patterns during startup flow with and without the injection of coolant are analyzed. An empirical relation for conventional nozzles has been applied to determine the transition pressure ratio. Actual transition flow from base to extension nozzle is found to be different from the calculated transition pressure ratio and flow transition occurs early in case of secondary injection. A large reduction in wall temperature is observed with the film flowing along the nozzle wall and it does not have any adverse effect on flow transition. Instead of efficiency, a film cooling effectiveness for high temperature flow is used to understand the effect of coolant temperature on reduction of heat flux and mixing characteristics. Mass flow rate of coolant is seen to have significant effect on mixing and flow separation.

      PubDate: 2018-05-10T11:13:17Z
      DOI: 10.1016/j.ast.2018.04.038
      Issue No: Vol. 78 (2018)
       
  • Influences of anisotropic fiber-reinforced composite media properties on
           fundamental guided wave mode behavior: A Legendre polynomial approach
    • Authors: Cherif Othmani; Anouar Njeh; Mohamed Hédi Ben Ghozlen
      Pages: 377 - 386
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Cherif Othmani, Anouar Njeh, Mohamed Hédi Ben Ghozlen
      The guided wave technique has been widely used for evaluating different structures. Recently, these acoustic waves have been implemented in non-destructive testing (NDT). Accordingly, these waves make up a set of motivated means for detecting defects because of their effectiveness for quickly testing a long series of specimens. On that account, the present article introduces a Legendre polynomial approach, for modeling guided dispersion curves solutions in anisotropic fiber-reinforced composite media. This polynomial approach offers a higher computational efficiency and simplicity in comparison to traditional methods. The validity of the proposed Legendre polynomial approach is illustrated by comparison with available data. The convergence of this method is discussed. Consequently, the computation time of the Legendre polynomial approach increases linearly when the number of truncation order M increases. In the same context, the computation time of this polynomial approach is compared to the ordinary differential equation (ODE) approach in terms of efficiency. In addition, the influence on the fundamental guided wave dispersion curves due to reductions in the material properties such as C 11 , C 12 , C 13 , C 22 , C 23 , C 33 , C 44 , C 55 , C 66 and mass density were analyzed for anisotropic fiber-reinforced single-layered composite media with different propagation angles. The studies were performed by obtaining the behavior guided wave dispersion curves for each single-layered type. This was done by reducing the material properties mentioned above by 50% from the original value. Since the guided wave dispersion curves in a single-layered composite media varies with the propagation direction, the layers were analyzed at 0°, 45° and 90° propagation angles, with all the aforementioned variations. The computer programs in this work are written by using Matlab software.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.04.041
      Issue No: Vol. 78 (2018)
       
  • Dual-polarized GPS antenna array algorithm to adaptively mitigate a large
           number of interference signals
    • Authors: Kwansik Park; Dongkook Lee; Jiwon Seo
      Pages: 387 - 396
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Kwansik Park, Dongkook Lee, Jiwon Seo
      Intentional or unintentional interference experienced by the Global Positioning System (GPS) is a significant concern for GPS-based critical infrastructures and services including aviation. An effective way to mitigate GPS interference is to utilize a GPS antenna array capable of electronically changing its gain pattern. Although a conventional GPS antenna array consists of single-polarized antenna elements, a dual-polarized antenna array has the potential to mitigate approximately twice the number of interference signals in the spatial domain as a single-polarized array because of the additional degrees of freedom provided. This paper proposes an adaptive beamforming algorithm using a dual-polarized GPS antenna array for mitigation of interference signals with various polarizations. In this paper, a dual-polarized antenna element specifically refers to two co-located crossed linearly polarized dipole antennas. The proposed minimum-variance-distortionless-response (MVDR)-based space–time adaptive processing (STAP) method utilizes a novel constraint vector that is specially designed for a dual-polarized GPS array. As the proposed constraint vector considers realistic radiation patterns of the antenna, the performance of the proposed method in terms of the signal-to-interference-plus-noise power ratio (SINR) is noticeably superior to that of previous methods under a representative interference scenario. The performance of the proposed method is compared with three previous methods utilizing dual-polarized antenna arrays.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.04.029
      Issue No: Vol. 78 (2018)
       
  • Modeling of incomplete combustion in a scramjet engine
    • Authors: Jae Won Kim; Oh Joon Kwon
      Pages: 397 - 402
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Jae Won Kim, Oh Joon Kwon
      In the present study, an empirical theoretical split chemistry model was developed to describe the phenomenon of incomplete combustion for scramjet engines. The model was developed by decoupling flow into two distinct regions, namely, unburned and burned, as in real scramjet flows. The conservation equations for the combustor and the rate equations for the supersonic nozzle were calculated independently for these two regions using the split ratio of the volume occupied by the fuel–air mixture to the overall volume. The split chemistry model was implemented in a one-dimensional flow solver by assuming that the combustion efficiency is known. The effect of incomplete combustion on the performance of a hydrocarbon-fueled scramjet engine was investigated by performing a parametric study along the entire flow path through the scramjet engine, including the inlet, isolator, combustor, and supersonic nozzle. The results showed that, for a combustion efficiency of 0.5 with a global equivalence ratio of 0.5, the overall temperature and the thrust performance along the flow path through the combustor and the nozzle significantly decrease owing to incomplete combustion. It was also observed that the chemical composition of the fuel-only region varies, regardless of the change in combustion efficiency, because efficiency is a function of the extent of the combustion reaction and the split ratio. It was found that the present split chemistry model is useful to describe incomplete combustion, and it can be effectively utilized for the preliminary design and analysis of scramjet engines.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.04.044
      Issue No: Vol. 78 (2018)
       
  • Fault detection and isolation of satellite gyroscopes using relative
           positions in formation flying
    • Authors: Amir Shakouri; Nima Assadian
      Pages: 403 - 417
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Amir Shakouri, Nima Assadian
      A fault detection and isolation method for satellite rate gyros is proposed based on using the satellite-to-satellite measurements such as relative position beside orbit parameters of the primary satellite. By finding a constant of motion, it is shown that the dynamic states in a relative motion are restricted in such a way that the angular velocity vector of primary satellite lies on a quadratic surface. This constant of motion is then used to detect the gyroscope faults and estimate the corresponding scale factor or bias values of the rate gyros of the primary satellite. The proposed algorithm works even in time variant fault situations as well, and does not impose any additional subsystems to formation flying satellites. Monte-Carlo simulations are used to ensure that the algorithm retains its performance in the presence of uncertainties. In presence of only measurement noise, the isolation process performs well by selecting a proper threshold. However, the isolation performance degrades as the scale factor approaches unity or bias approaches zero. Finally, the effect of orbital perturbations on isolation process is investigated by including the effect of zonal harmonics as well as drag and without loss of generality, it is shown that the perturbation effects are negligible.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.04.039
      Issue No: Vol. 78 (2018)
       
  • Numerical analysis of supersonic flows over an aft-ramped open-mode cavity
    • Authors: Zhaoxin Ren; Bing Wang; Bowen Hu; Longxi Zheng
      Pages: 427 - 437
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Zhaoxin Ren, Bing Wang, Bowen Hu, Longxi Zheng
      The characteristics of supersonic cavity flows were investigated using large eddy simulation together with the acoustic analogy method. A fifth-order hybrid compact-weighted essentially non-oscillatory scheme was applied to calculate the convective flux, and a sixth-order compact scheme was used for the viscous flux. Farassat's Formula 1A was used to solve the Ffowcs William–Hawkings equations to obtain the far-field acoustic pressure fluctuations. The effects of cavity configuration and flow Mach number on the pressure waves generated by the interaction of shear vortices and cavity were compared. The ramped rear-step of the cavity can increase the more-organized level of flow coherent structures, and decrease the static pressure distribution on the cavity bottom-wall. The attenuation of the interactions between the shear layer vortex and the aft-ramped wall of the cavity can reduce the feedback of pressure waves upstream. The energy of the main frequency significantly decreases for the far-field acoustics in the upstream flow over the ramped rear-step cavity. Thus, the effectiveness of noise reduction by the rear-ramp is considerable for the area upstream of the cavity for the present conditions, but it is not the case opposite to and downstream of the cavity. The present conclusions are valuable for evaluating the performance of noise suppression by cavities embedded in supersonic inflows in engineering applications.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.05.003
      Issue No: Vol. 78 (2018)
       
  • Dynamic analysis of functionally graded carbon nanotubes-reinforced plate
           and shell structures using a double directors finite shell element
    • Authors: A. Frikha; S. Zghal; F. Dammak
      Pages: 438 - 451
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): A. Frikha, S. Zghal, F. Dammak
      The present paper aims at the study of the dynamic behavior of functionally graded carbon nanotubes-reinforced composite shell structures (FG-CNTRC) via forced vibration analysis. The governing equations of motion are developed using a linear discrete double directors finite element model. The elaborated model is based on high-order-distribution of displacement field and uses a cubic variation of the vector position along the thickness direction. A zero transverse shear stress at top and bottom surfaces is also imposed. Four types of distributions of carbon nanotubes (CNTs) such that uniformly and three functionally graded distributions are considered. The extended rule of mixture is used to estimate the effective material properties of carbon nanotube-reinforced composite (CNTRC) shell. The applicability and the performance of the present model are illustrated by three numerical examples of FG-CNTRC square plates, spherical caps and annular ring plates. The transient center deflections of the studied shell structures are computed and depicted for different volume fractions and profiles of CNTs, various boundary conditions and other geometrical parameters in order to show the effect of these parameters on dynamic behavior of FG-CNTRC shells.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.04.048
      Issue No: Vol. 78 (2018)
       
  • Virtual-command-based model reference adaptive control for abrupt
           structurally damaged aircraft
    • Authors: Jing Zhang; Xiaoke Yang; Lingyu Yang
      Pages: 452 - 460
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Jing Zhang, Xiaoke Yang, Lingyu Yang
      Although a high-gain learning rate can offer ideal tracking performance in adaptive control in theory, it can also lead to high-frequency oscillations in practice due to the unmodeled dynamics of the system. In aircraft structural damage scenarios, the strong uncertainty and the safety-critical nature of the problem make this conflict critical. In this paper, a novel virtual-command-based model reference adaptive control (MRAC) scheme for flight control is proposed. In the new framework, the direct relationship between the learning law and the actual tracking error is broken; instead, a virtual command is introduced as the input to the standard MRAC controller. The key feature is that even when the virtual tracking error is large, the actual tracking error can be maintained within a small range; thus, the MRAC learning rate does not necessarily need to be large to suppress the virtual transient tracking error, which is greatly beneficial for the robustness of the MRAC controller. The proposed method is illustrated by the attitude control of the 6-DOF nonlinear Generic Transport Model in a scenario with a broken left wing tip.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.04.043
      Issue No: Vol. 78 (2018)
       
  • Numerical and experimental investigation of fitting tolerance effects on
           damage and failure of CFRP/Ti double-lap single-bolt joints
    • Authors: Yuejie Cao; Zengqiang Cao; Yangjie Zuo; Lubin Huo; Jianping Qiu; Duquan Zuo
      Pages: 461 - 470
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Yuejie Cao, Zengqiang Cao, Yangjie Zuo, Lubin Huo, Jianping Qiu, Duquan Zuo
      CFRP/Ti bolted joints are increasingly used in aircraft structures. Optimizing the joint design is vital for overall composite structure designs. Therefore, a progressive damage model was developed for investigating the effects of clearance and interference sizes on the damage and failure of CFRP/Ti double-lap, single-bolt joints under quasi-static loads, in which the improved three dimensional Hashin failure criterion and Tan degradation rules were used through an ABAQUS user-define-field (USDFLD) subroutine. The corresponding quasi-static tensile tests and fatigue tests were also conducted. Joints strength were evaluated and failure mechanism was discussed. Numerical results showed that the matrix compression failure dominated the joint failure mode. Joint ultimate strength decreased gradually with the increase of clearance sizes, while joint bearing strength and stiffness exhibited an increase with interference sizes at first and then decreased rapidly due to the initial installation damage. Moreover, the maximum strength was achieved at the interference size of 0.5%. Those results were in well agreement with corresponding experimental results. In addition, interference sizes were also revealed a correlation with the fatigue life of the joints. The study presented here will be useful for optimization of composite structure designs.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.04.042
      Issue No: Vol. 78 (2018)
       
  • Buckling analysis of two-directionally porous beam
    • Authors: Haishan Tang; Li Li; Yujin Hu
      Pages: 471 - 479
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Haishan Tang, Li Li, Yujin Hu
      In this paper, buckling analysis of two-directionally porous beam is conducted. Based on the available results of Young's modulus and mass density via Gaussian random field theory, a new two-directionally porous beam model is developed. With the help of Euler–Bernoulli beam theory and minimum total potential energy principle, the equilibrium equations for nonlinear and linear buckling are derived. The numerical solutions of critical buckling loads for different porosity distribution patterns can be obtained by generalized differential quadrature method. The final numerical results exhibit that more porosities near the middle surface or the two edges of beam can lead to a larger critical buckling load when the same total volume fraction of porosity is in different porosity distribution patterns. The effect of porosity distribution in thickness direction is more dominated on the critical buckling load than that of the axial porosity distribution. Moreover, the critical buckling load becomes more sensitive to aspect ratio of beam and total volume fraction of the porosity when increasing mode number. The critical buckling load of two-directionally porous beam depends not only on bending coefficient (like the one-directionally porous beam), but also on first and second derivatives of the bending coefficient.

      PubDate: 2018-05-17T11:29:52Z
      DOI: 10.1016/j.ast.2018.04.045
      Issue No: Vol. 78 (2018)
       
  • Steepest descent quaternion attitude estimator
    • Authors: Pawel Zagorski; Tomasz Dziwinski; Andrzej Tutaj
      Pages: 1 - 10
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Pawel Zagorski, Tomasz Dziwinski, Andrzej Tutaj
      A new computationally inexpensive attitude determination algorithm based on the minimization of Wahba's loss function is presented in the paper. The estimation problem is converted into quaternion representation and solved with iterative prediction–correction scheme. Unlike Kalman filter approach, an iterative gradient optimization is used to estimate the attitude quaternion and gyroscope bias. Algorithm derivation is shown and its performance is tested. The presented case study assumes configuration with three types of sensors: Sun sensors with full angular coverage, a magnetometer and a MEMS rate gyroscope. Sensor model parameters are selected to mimic a pico or nano class satellite. Orbital environment is simulated with the Bouvier–Lyddane orbit model, the IGRF magnetic field model and geometric properties of the Earth–Sun system. Periodical loss of Sun sensor data due to eclipses is taken into account. Based on the presented case study a proposition of tuning procedure and a brief comment on algorithm stability are given. The tuning approach trades off estimate convergence versus noise rejection property. In a Monte Carlo test the proposed algorithm compares well against an EKF with an attitude error within 0.1 deg in sunlight and 0.4 deg in the eclipse. Finally, a simulation showing a possibility of operating the SDQAE algorithm while sampling each of the sensors at different rate is presented.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.01.030
      Issue No: Vol. 77 (2018)
       
  • Uncertainty propagation in aerodynamic forces and heating analysis for
           hypersonic vehicles with uncertain-but-bounded geometric parameters
    • Authors: Yuning Zheng; Zhiping Qiu
      Pages: 11 - 24
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Yuning Zheng, Zhiping Qiu
      In this study, uncertainties in aerodynamic forces and heating properties of hypersonic vehicles are calculated and analyzed with consideration of uncertain-but-bounded geometric parameters. The aerodynamic shape of a hypersonic vehicle is created with a few geometric parameters containing physical meanings after applying the class and shape transformation (CST) method. Considering uncertainties in geometric parameters caused by manufacturing errors, interval variables are introduced to quantify geometric parameters and a novel interval-based CST method (ICST) is proposed to represent the uncertain aerodynamic shape. By means of hypersonic engineering methods, aerodynamic forces and heating properties of hypersonic vehicles can be predicted. The interval analysis method and novel Bernstein-polynomial-based method for calculating the lower and upper bounds of aerodynamic forces and heating properties are developed. The results of analyzing two numerical examples demonstrate the effectiveness and feasibility of the proposed method and further confirm the necessity of accounting for the uncertainties in geometric parameters when investigating aerodynamic forces and heating properties of hypersonic vehicles.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.028
      Issue No: Vol. 77 (2018)
       
  • Numerical study on solid-fuel scramjet combustor with fuel-rich hot gas
    • Authors: Xiang Zhao; Zhi-xun Xia; Bing Liu; Zhong Lv; Li-kun Ma
      Pages: 25 - 33
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Xiang Zhao, Zhi-xun Xia, Bing Liu, Zhong Lv, Li-kun Ma
      Solid-fuel scramjet combustor with cavity faces challenges of ignition and flame holding. In the current study, a novel concept, solid-fuel scramjet combustor with fuel-rich hot gas, is proposed. The Reynolds-average Navier–Stokes (RANS) equations coupled with the SST k − ω turbulence model and the second-order spatially accurate upwind scheme are employed to calculate its flow field. The feasibility of the solid-fuel scramjet combustor with fuel-rich hot gas is studied based on the validation of numerical method. The comparison of the performance is made between the combustor with fuel-rich gas and the combustor with cavity. Various parameters, namely excess air coefficient of gas generator and mass flow rate of fuel-rich gas, are studied, and their effects on the combustion efficiency, total pressure recovery and fuel regression rate are analyzed. This is the basic study for experiments of a solid-fuel scramjet combustor with fuel-rich hot gas.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2017.12.024
      Issue No: Vol. 77 (2018)
       
  • An application of Deep Neural Networks to the in-flight parameter
           identification for detection and characterization of aircraft icing
    • Authors: Yiqun Dong
      Pages: 34 - 49
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Yiqun Dong
      This paper applies the Deep Neural Networks to the in-flight parameter identification for detection and characterization of the aircraft icing. General dynamics of the aircraft are firstly presented, ice effects on the dynamics are characterized. Deep Neural Networks (DNNs) including Convolutional Neural Network (CNN) and Recurrent Neural Network (RNN) are briefly introduced. We propose a “state-image” approach for the pre-processing of the input flight state, then we design a DNN structure which models both local connectivity (using CNN) and temporal characteristics (using RNN) of the flight state. The identified parameters are exported from the DNN output layer directly. To fully evaluate the performance of the DNN-based approach, we conduct simulation tests for different cases which correspond to clean and aircraft icing at different locations (wing, tail, wing and tail) with different severities (moderate, severe). A comparison of the DNN-based approach with a baseline H ∞ -based identification algorithm (state-of-the-art for aircraft icing) is also delivered. Based on the test and comparison results, the DNN-based approach yields more accurate identification performance for more parameters, which shows promising applicability to the in-flight parameter identification problem.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.026
      Issue No: Vol. 77 (2018)
       
  • Extending slide-slip mesh update method to finite volume method
    • Authors: Kun Qu; Feng Xie; Jinsheng Cai
      Pages: 50 - 57
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Kun Qu, Feng Xie, Jinsheng Cai
      For simulations of flows around rotating bodies, usually sliding mesh method or overset grid method is used. But both of them have to perform inter-mesh interpolation which introduces much numerical error and usually violates conservation. Shear-slip mesh update method (SSMUM) is another method for such flows. In each time step of SSMUM, a mesh slipping step follows a mesh deforming step to undo the deformation and results in a new mesh of good quality. Each vertex on the slipping interface can only move from one node to the next node in the circumference, which makes the interface always conformal and no need for inter-mesh interpolation. However, SSMUM didn't get enough attention in the community of finite volume method. In this paper, SSMUM is extended to cell center finite volume method. To guarantee conservation and obtain high order accuracy on a slipping interface, a remapping procedure is needed to transfer flow field from an old mesh to a new mesh. This was achieved by solving a linear convective PDE with one or two explicit steps, thus only resulting in little extra computing cost. Oscillating NACA0012 airfoil was simulated with the improved SSMUM. The results showed excellent agreement with the data by rigid rotating mesh. And the flow field was always smooth. It suggests that this improved SSMUM has advantages in getting conservative, smooth and high accuracy solutions for rotating problems.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.025
      Issue No: Vol. 77 (2018)
       
  • Studies on effusion cooling: Impact of geometric parameters on cooling
           effectiveness and coolant consumption
    • Authors: Vishal Venkatesh; Sriraam J.; Bala Vignesh D.; Subash K.; Ratna Kishore Velamati; Srikrishnan A.R.; Balajee Ramakrishnananda; Suresh Batchu
      Pages: 58 - 66
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Vishal Venkatesh, Sriraam J., Bala Vignesh D., Subash K., Ratna Kishore Velamati, Srikrishnan A.R., Balajee Ramakrishnananda, Suresh Batchu
      This study is focused on the impact of certain important geometric parameters on cooling effectiveness and coolant consumption for effusion cooling of aircraft combustor liner. The three dimensional turbulent flow field in a domain representing the combustor with several rows of effusion coolant injection is considered for the analysis. The geometric parameters considered are: angle of injection of the coolant, axial and transverse pitch of the injection holes, hole spacing and hole diameter. Also, based on the analysis of the temperature field within the chamber, a novel concept of ‘variable hole diameter’ has been introduced to reduce coolant consumption. A symmetric 3D computational model including the combustion chamber, coolant chamber and the effusion plate was used for the study. Conjugate heat transfer was modeled between the effusion-cooled wall and the two chambers. A detailed mass flow rate analysis has been performed for the various cases in order to study the impact of parameters on coolant consumption. The proposed approach of using an effusion plate with variable hole diameters is found to be effective in reducing the net coolant consumption significantly while maintaining a given level of cooling effectiveness.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2017.12.044
      Issue No: Vol. 77 (2018)
       
  • Performance assessment of electrically driven pump-fed LOX/kerosene cycle
           rocket engine: Comparison with gas generator cycle
    • Authors: Hyun-Duck Kwak; Sejin Kwon; Chang-Ho Choi
      Pages: 67 - 82
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Hyun-Duck Kwak, Sejin Kwon, Chang-Ho Choi
      An electrically driven pump-fed cycle for rocket engine is proposed and a viability of the proposed cycle is assessed compared to a gas generator cycle. The maximum possible thrust level is determined considering the technological maturity of the electric motor. Four types of battery cells were assessed in a screening test for the proposed cycle and the necessity of regenerative cooling for the battery pack is shown. The mass expressions of the proposed cycle and gas generator cycle are derived in terms of pump power and burning time. The basic features are demonstrated with respect to combustion chamber pressure, burning time, and thrust level. The results show that it is favorable to maintain a lower combustion chamber pressure, a longer burning time, and a higher thrust level to remedy the payload penalty incurred when the gas generator cycle is not used. In addition to focusing on the battery pack, the regenerative cooling effect on the battery pack mass is discussed. Further, the impact of optimal battery cell discharge time on the payload is explained. To estimate the payload for the proposed cycle quantitatively, hypothetical low earth orbit (LEO) and KSLV-II sun synchronous orbit (SSO) mission cases are used. In the analysis of the hypothetical LEO mission, it is found that the proposed cycle payloads are only 2.1% to 3.5% lower than those of the gas generator cycle when the combustion chamber pressure is 3.0 MPaA. For the KSLV-II SSO mission, the cargo payload is increased by 3.7% compared to that of gas generator cycle if the proposed cycle is employed for the third-stage engine.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.033
      Issue No: Vol. 77 (2018)
       
  • Combustion stabilizations in a liquid kerosene fueled supersonic combustor
           equipped with an integrated pilot strut
    • Authors: Junlong Zhang; Juntao Chang; Wen Shi; Wenxin Hou; Wen Bao
      Pages: 83 - 91
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Junlong Zhang, Juntao Chang, Wen Shi, Wenxin Hou, Wen Bao
      The numerical and experimental investigations have been conducted to test a newly designed integrated pilot strut. The integrated pilot strut consists of two neighboring small strut with shallow cavities, with the help of which, the fuel injection and flame holding are achieved in the supersonic combustor. The flowing characteristics in the internal flow duct of the pilot strut are evaluated with the numerical simulation method, results proving that a lower speed zone generates in the internal flow duct in the supersonic combustor and the local equivalence ratio in the low speed zone is suitable for combustion. Then, a series of experiments have been conducted in the flight condition of Ma = 5 , with stagnation state T t = 1270 K, P t = 1.20 MPa. Experimental results show that a pilot flame generates in the internal flow duct of the pilot strut, based on which, the main fuel injected from the sidewall of the strut is ignited, and the global flame is established in the whole combustor. The combustion of the main fuel leads to a thermal chocking at the exit of the strut. Further, the thermal chocking is beneficial to the self-stabilization of the pilot flame. With the combustion organization strategy of the pilot strut flame holding, the global flame is stabilized in a wide range of equivalence ratio changing from 0.15 to 0.75 in the supersonic combustor, and the combustion characteristics in different equivalence ratios are analyzed in this paper. The integrated combustion organization approach by the pilot strut with internal cavities is demonstrated feasible and a high combustion performance is obtained.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.035
      Issue No: Vol. 77 (2018)
       
  • Disturbance observer based reliable H∞ fuzzy attitude tracking control
           for Mars entry vehicles with actuator failures
    • Authors: Huai-Ning Wu; Zi-Peng Wang; Lei Guo
      Pages: 92 - 104
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Huai-Ning Wu, Zi-Peng Wang, Lei Guo
      This paper introduces a disturbance observer (DO) based reliable H ∞ fuzzy attitude tracking control design for Mars entry vehicles with actuator failures. Initially, to reduce the complexity of Takagi–Sugeno (T–S) fuzzy modeling, the two time-scale decomposition technique is used to divide the original nonlinear attitude tracking error model of Mars entry vehicles into a slow subsystem describing the attitude kinematics and a fast subsystem describing the attitude dynamics. The dynamic inversion control (DIC) method is subsequently applied to the slow subsystem to generate the angular velocity command. Then, the T–S fuzzy modeling method is employed to exactly represent the fast subsystem and a disturbance observer (DO) is constructed to estimate the modeled disturbance based on the derived tracking error fuzzy system of angular velocity. By the technique of linear matrix inequalities (LMIs), a DO based reliable H ∞ fuzzy controller of attitude tracking is developed to stabilize exponentially the angular velocity tracking error and the modeled-disturbance state estimation error with an H ∞ tracking performance both in nominal and actuator failure cases. Furthermore, it is shown that the original nonlinear tracking error system is also exponentially stable and satisfies an H ∞ tracking performance both in nominal and actuator failure cases under the proposed fuzzy control law together with the DIC law, provided that the timescale separation between the fast and slow subsystems is valid. Finally, simulation results illustrate the effectiveness of the proposed design method.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.032
      Issue No: Vol. 77 (2018)
       
  • Improved polar inertial navigation algorithm based on pseudo INS
           mechanization
    • Authors: Meng Liu; Guangchun Li; Yanbin Gao; Shutong Li; Qingwen Meng; Shitong Du
      Pages: 105 - 116
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Meng Liu, Guangchun Li, Yanbin Gao, Shutong Li, Qingwen Meng, Shitong Du
      From the perspective of global inertial navigation system (INS), an improved inertial navigation algorithm is proposed to solve the navigation problem in polar regions. The implementation of navigation system is achieved with two executive units, navigation calculation (NC) unit and parameter transformation (PT) unit. The NC unit is executed autonomously with pseudo INS mechanization under the spherical Earth model. The pseudo INS mechanization is established with the pseudo-Earth frame, which is a generalized Earth frame and is reconstructed based on the switching position selected properly with the motion range of vehicle. Then, the smooth switching of navigation frame and the intrinsic unity of navigation algorithm can be achieved, thereby further unifying the polar navigation algorithm for both strapdown INS and platform INS in a brief form in global regions. On the other hand, the PT units are employed to correct and transform navigation parameters to a corresponding coordinate system with ellipsoidal Earth model and can be conducted simultaneously in parallel, thereby ensuring the navigation accuracy and communicating with other local navigation systems conveniently. Theoretical analysis and numerical results indicate the validity of the proposed algorithm.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.029
      Issue No: Vol. 77 (2018)
       
  • An integrated load sensing valve-controlled actuator based on
           power-by-wire for aircraft structural test
    • Authors: Yaoxing Shang; Xiaochao Liu; Zongxia Jiao; Shuai Wu
      Pages: 117 - 128
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Yaoxing Shang, Xiaochao Liu, Zongxia Jiao, Shuai Wu
      The traditional loading system, for the full-sized aircraft structure test, requires the centralized hydraulic power supply and the distributed valve-controlled cylinder, which leads to complex and large pipeline systems. The layout reconfiguration process of the test platform is quite laborious. Moreover, the loading system efficiency is quiet low because of both the huge overflow loss and the huge throttling loss of the traditional valve-controlled system. In order to conduct the structure test more efficiently, this paper proposes a novel integrated Load Sensing Valve-Controlled Actuator (LSVCA) with high efficiency and low energy consumption, which can reduce the overflow loss by the intermittent operation of the motor and reduce the throttling loss by the variation of the supply pressure. It also simplifies the test platform reconfiguration due to its high-level integration and Power-By-Wire (PBW) feature. In this paper, the hydraulic working principle and the energy-saving analysis of the LSVCA is proposed. In order to verify the feasibility of the new principle and the effectiveness of the high efficiency, the mathematical model of the LSVCA is established. Furthermore, an experimental prototype of the LSVCA is tested. Test results indicate that the LSVCA is adequate to satisfy the criteria for full-sized aircraft structure test. The throttling efficiency of the LSVCA loading system is 1.75 times of the efficiency of the traditional loading system under the low-level load pressure condition.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.030
      Issue No: Vol. 77 (2018)
       
  • Receding horizon guidance of a small unmanned aerial vehicle for planar
           reference path following
    • Authors: Yoshiro Hamada; Taro Tsukamoto; Shinji Ishimoto
      Pages: 129 - 137
      Abstract: Publication date: June 2018
      Source:Aerospace Science and Technology, Volume 77
      Author(s): Yoshiro Hamada, Taro Tsukamoto, Shinji Ishimoto
      This paper describes a novel lateral guidance law for an unmanned aerial vehicle using nonlinear receding horizon optimization and shows its flight test results. The guidance law uses an extended Kalman filter which estimates steady wind velocities in order to follow a pre-specified reference path defined in a ground-fixed coordinate system. The guidance law can be applied to arbitrary reference path as long as the path is represented as a differentiable function of x and y in a ground-fixed coordinate system. A small-scale research vehicle developed by the Japan Aerospace Exploration Agency is used for flight tests, and the results demonstrate the high guidance performance of the proposed method.

      PubDate: 2018-04-15T07:30:57Z
      DOI: 10.1016/j.ast.2018.02.039
      Issue No: Vol. 77 (2018)
       
  • A novel ambiguity search algorithm for high accuracy differential GNSS
           relative positioning
    • Authors: Yang
      Abstract: Publication date: July 2018
      Source:Aerospace Science and Technology, Volume 78
      Author(s): Yang Li
      It is well understood that the key to high accuracy differential global navigation satellite system (DGNSS) relative positioning is the resolution of the integer ambiguities within the carrier phase measurements and the continuous tracking of them. The resolution process is usually converted into an integer least square optimization problem, e.g., among them is the most notable Least-squares Ambiguity Decorrelation Adjustment (LAMBDA) algorithm. This paper adds additional statistical constraints to the existing LAMBDA approach to improve the performance of ambiguity resolution process when the LAMBDA ratio is below a certain predefined threshold. In order to fix the integer ambiguity as soon as possible, a novel ambiguity search algorithm is proposed, which is like the threshold based algorithm but explicitly exploits the correlation structure of the double difference covariance model and the measurement accuracy difference. To do that, the relationship between global navigation satellite system (GNSS) pseudorange measurement accuracy and the resolution of the integer ambiguity of carrier phase measurements is analyzed based on the GNSS distance measurement equations. Analytic statistical models of the single and double differences of the distance measurements are presented. Based on the analysis, it is found that the conventional choice of the highest elevation satellite as the reference satellite may not be a superior selection in single epoch algorithms. In fact, code phase measurements are used for ambiguity resolution, and the covariance of baseline vector is independent with reference satellite selection when the least square problem is optimally weighted. The novel ambiguity search algorithm is presented to fix the ambiguity as soon as possible. Simulation and field test data validate the analysis and the ambiguity search algorithm.

      PubDate: 2018-05-17T11:29:52Z
       
 
 
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