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  Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
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International Journal of Aerospace Engineering
Journal Prestige (SJR): 0.232
Citation Impact (citeScore): 1
Number of Followers: 87  

  This is an Open Access Journal Open Access journal
ISSN (Print) 1687-5966 - ISSN (Online) 1687-5974
Published by Hindawi Homepage  [339 journals]
  • Pilot Maneuvering Performance Analysis and Evaluation with Deep Learning

    • Abstract: Quick access recorder (QAR) data have been used to evaluate pilot performance for decades. However, traditional evaluation methods suffer from the inability to consider multiple parameters simultaneously, and most of them need to select features manually in advance. To study the relationship between QAR data and pilot performance, this paper puts forward one-dimensional convolutional neural networks (1-D CNN) which consider QAR metrics in an integrated manner. This paper obtained indicators describing the operational status of an aircraft first. Then, the correlation between indicators and pilot performance (skill levels) was studied. Inspired by the fact that CNN can extract both local and global features, this paper has developed an approach to achieve the state-of-the-art result in pilot performance evaluation, which was tested on operating data of Boeing 737. The results prove that other methods do not work well, while the 1-D CNN improves the prediction accuracy of 5 pilot skill levels. Besides, when it is used on a binary classification problem, the result improves to 78.18%. Finally, the indicators were grouped into 5 common factors by factor analysis and fed into 1-D CNN in different combinations. Each common factor plays a different role in pilot performance evaluation, which can provide advice for the future.
      PubDate: Wed, 15 Mar 2023 12:05:00 +000
  • The Pretension Design of Cable Mesh considering the Large Deformation of
           Ring Truss

    • Abstract: The conventional pretension design of cable mesh usually takes the ring truss as a rigid body or assumes small deformation. This method needs to be more accurate in designing super large aperture antennas. A cable mesh design method considering the large deformation of the ring truss is proposed in this paper based on the flexible multibody dynamics (FMD) and the force density method (FDM). With this method, the significant range deviation of the boundary points’ position of the ring truss under the tension of the external area of the cable mesh after the completion of the pretension design can be predicted with high accuracy. After the ring truss and cable mesh surface are assembled stably, there is only a minimal deviation between the actual mesh surface and the theoretical mesh surface of the antenna, and there is only a minimal deviation between the genuine mesh pretension and the design pretension. The above calculation method is verified by numerical simulation, and the simulation results show that the technique can be applied to the mesh pretension design of a super large aperture ring deployable antenna.
      PubDate: Sat, 11 Mar 2023 08:05:01 +000
  • A Modified Robust Adaptive Fault Compensation Design for Spacecraft with
           Guaranteed Transient Performance

    • Abstract: A modified, robust adaptive fault compensation design is proposed for rigid spacecraft systems with uncertain actuator failures and unknown disturbances. The feedback linearization method is first introduced to linearize the nonlinear dynamics, and a model-reference adaptive controller is designed to suppress the unknown external disturbances and stabilize the linearized system. Then, a composite adaptive controller is developed by integrating multiple controllers designed for the corresponding actuator failure conditions, which can handle the essentially multiple uncertainties (failure time, values, type, and failure pattern) of actuator failures simultaneously. To further improve the transient performance problem in the failure compensation control, an H∞ compensator is introduced as an additional item in the basic controller to attenuate the adverse effects on tracking performance caused by parameter estimation errors. From the theoretical analysis and simulation results, it is obvious that the designed scheme can not only guarantee the stability of the closed-loop system is stable and asymptotical tracking properties for a given reference signal but also greatly improve the transient performance of the spacecraft system during the process of failure compensation.
      PubDate: Tue, 07 Mar 2023 05:35:02 +000
  • Integrated Navigation Method of Aerospace Vehicle Based on Rank Statistics

    • Abstract: The large dynamic and high-speed flight of aerospace vehicle will bring unpredictable conditions to its navigation system, resulting in that its system random noise probability distribution will no longer meet the preconditions of Gaussian distribution preset by the existing filter algorithm, thus reducing the accuracy of the navigation system. So, it is very important to propose an effective method to solve the filter problem of the navigation system in non-Gaussian distribution to improve the accuracy of the navigation system. Therefore, an integrated navigation method of aerospace vehicle based on rank statistics (LRF) has been proposed in this paper. Firstly, based on the flight characteristics of aerospace vehicles, an accurate gravity calculation model has been established to improve the accuracy of system modelling. Then, the state equation and measurement equation of integrated navigation system have been established. In combination with the rank filter algorithm as well as the determined weights, sampling points are calculated and nonlinearly propagated through the transition matrix to achieve an accurate estimation about the predicted values of the state quantities and measurement quantities and the covariance matrix. In turn, it simulates the probability distribution of the system state effectively. Therefore, when the system random noise probability distribution of the aerospace vehicle does not meet the Gaussian distribution due to various interference factors in the actual flight process, the algorithm can simulate the probability distribution of the actual system to the greatest extent, to improve the accuracy of the integrated navigation system and enhance the reliability of the navigation system ultimately.
      PubDate: Tue, 07 Mar 2023 05:35:01 +000
  • Intelligent Online Multiconstrained Reentry Guidance Based on Hindsight
           Experience Replay

    • Abstract: Traditional guidance algorithms for hypersonic glide vehicles face the challenge of real-time requirements and robustness to multiple deviations or tasks. In this paper, an intelligent online multiconstrained reentry guidance is proposed to strikingly reduce computational burden and enhance the effectiveness with multiple constraints. First, the simulation environment of reentry including dynamics, multiconstraints, and control variables is built. Different from traditional decoupling methods, the bank angle command including its magnitude and sign is designed as the sole guidance variable. Secondly, a policy neural network is designed to output end-to-end guidance commands. By transforming the reentry process into a Markov Decision Process (MDP), the policy network can be trained by deep reinforcement learning (DRL). To address the sparse reward issue caused by multiconstraints, the improved Hindsight Experience Replay (HER) method is adaptively combined with Deep Deterministic Policy Gradient (DDPG) algorithm by transforming multiconstraints into multigoals. As a result, the novel training algorithm can realize higher utilization of failed data and improve the rate of convergence. Finally, simulations for typical scenes show that the policy network in the proposed guidance can output effective commands in much less time than the traditional method. The guidance is robust to initial bias, different targets, and online aerodynamic deviation.
      PubDate: Mon, 06 Mar 2023 06:20:00 +000
  • A Moving Target Online Location Algorithm Based on Factor Graph

    • Abstract: The superior performance of factor graphs compared to Kalman filtering in various fields and the use of factor graph algorithms instead of Kalman filtering algorithms in moving target localization tasks can reduce target localization error by more than 50%. However, the global factor graph algorithm may cause computational delays due to excessive computational effort. A moving target localization algorithm based on a combination of global and incremental optimization with improved factor graphs is proposed to improve localization accuracy and ensure that the computation time can be adapted to the requirements of online location. A reference point is introduced into the incremental calculation process, and it is first determined whether global or incremental calculation is used for this calculation by comparing the distance between the incremental localization results of the calculated reference point. The position of the UAV itself is then corrected by determining the position of the reference point, and this is used to finally locate the target. Simulation results show that the algorithm has good real-time performance compared to the time-consuming global algorithm. The online localization error of moving targets can be reduced by 17% compared to the incremental calculation results of the classical factor graph algorithm.
      PubDate: Fri, 03 Mar 2023 14:05:01 +000
  • A Modified Strain-Rate-Dependent Spring-Mass Model for Response Prediction
           of Composite Laminates Subjected to Low-Velocity Impact

    • Abstract: A modified strain-rate dependent (SRD) spring-mass model was first developed to capture the strain rate effect on response prediction of fiber-reinforced polymer (FRP) laminates subjected to low-velocity impact (LVI). The constitutive relations of FRP material were modified with the impact-induced strain rate using Yen-Caiazzo’s function in space and time dimensions simultaneously. The stiffness coefficients of the spring-mass model were updated step-by-step during solving the Bubnov-Galerkin equation by the variational method, allowing the SRD contact history to be obtained via recursive integration. The SRD expressions of stiffness coefficients under four typical boundary conditions were presented. Drop-weight tests on FRP laminates and corresponding VUMAT-based LVI simulation with the finite element method (FEM) were provided to prove the validity of the proposed SRD model in evaluating the strain rate effect on the LVI response of composites. Further parameter studies were carried out to investigate the reliability of the proposed SRD model for evaluating the influence of reinforced fibers with different strain rate dependency on impact response. The proposed lumped parameter model has been proven to be more efficient than the traditional FEM, which can be combined with some existing damage models to accurately analyze the delamination evolution process of FRP laminates under LVI in further studies.
      PubDate: Thu, 02 Mar 2023 14:35:01 +000
  • Automatic Task Planning and Its On-Orbit Verification of Agile Remote
           Sensing Satellite

    • Abstract: An on-board autonomous task planning system is designed and implemented in this article, aiming at the problem that the current remote sensing satellite needs complex instruction support to perform tasks and depends on the ground system too much. The complex earth observation task description and injection decomposition modules are designed in the system. No more than 128 ordered points describe the curve area task or irregular polygon area task, and the complex task is decomposed into several strips according to the satellite imaging width. Then, the task’s orbit, attitude, mobility, energy, and time constraints are calculated through the modules of on-board orbit prediction, agile attitude calculation, track planning, energy prediction, and visible arc calculation. Finally, the on-board autonomous task planning and execution are completed through task solution space search and metatask command generation modules. The on-orbit flight verification is carried out on the high-resolution multimode (GFDM) satellite. The results show that this paper’s on-board autonomous task planning system can complete complex task injection and autonomous planning and finally execute.
      PubDate: Tue, 28 Feb 2023 13:35:00 +000
  • Aerodynamic Parameter Identification of Projectile Based on Improved
           Extreme Learning Machine and Ensemble Learning Theory

    • Abstract: The firing accuracy of the projectile has a positive relation with aerodynamic parameters. Due to the complex dynamic characteristics of projectiles, there is an overfitting risk when a single extreme learning machine (ELM) is used to identify the aerodynamic parameters of the projectile, and the identification results oscillate transonic region. To obtain the aerodynamic parameters of the projectile accurately, an aerodynamic parameter identification model based on ensemble learning theory and ELM optimized by improved particle swarm optimization is proposed. The improved particle swarm optimization algorithm (IPSO) with an adaptive update strategy is used to optimize the weight and threshold of ELM. Combined with the ensemble learning theory, the improved ELM neural network is regarded as a weak learner to generate a strong learner. The structural parameters of the strong learner were continuously optimized through training, and an aerodynamic parameter identification model of projectile based on ensemble learning theory is obtained. The simulation results show that the introduction of the IPSO and ensemble learning theory enables the model to exhibit excellent generalization ability. The proposed identification model can accurately describe the variation of aerodynamic parameters with the Mach number.
      PubDate: Mon, 27 Feb 2023 13:05:00 +000
  • Design, Computational Aerodynamic, Aerostructural, and Control Stability
           Investigations of VTOL-Configured Hybrid Blended Wing Body-Based Unmanned
           Aerial Vehicle for Intruder Inspections

    • Abstract: Unmanned aerial vehicles (UAVs) are gaining in popularity and sophistication in today’s modern world. UAVs are now available in a wide range of configurations. A UAV’s many applications include aerial photography and videography and target tracking. The upward-pointing propellers of some modern fixed-wing UAVs make it possible for them to take off and land vertically. Surveillance and intruder inspections are two areas where the blended wing body (BWB) configuration shines. This is because its weight is spread uniformly throughout the body, its radar signal is weaker than that of alternative configurations, and there is a relatively small amount of interference with its movement. With common design factors in mind, like vertical takeoff and landing, aerodynamic drag, and fundamental wing stability, the optimal BWB plan form for surveillance is designed. CATIA is used to finish the conceptual design of the BWB-based UAV. A fluid-structure interaction (FSI) study is carried out after the model has been examined in ANSYS Fluent. The UAV’s responsiveness is improved through simulation in the MATLAB environment after a proportional-integral-derivative-type altitude controller was developed. The results demonstrate that providing the UAV with an altitude instruction enhances its performance. Given the flexibility of the suggested BWB UAV’s design, we have decided to limit its maximum forward speed to 75 m/s and its maximum rate of vertical ascension to 50 m/s. Rapid BWB UAVs like the one seen here are quite helpful in dangerous situations.
      PubDate: Fri, 24 Feb 2023 08:05:00 +000
  • Effects of the Shock Wave Structure on the Tip Clearance Leakage Flow in
           Transonic Compressor Rotors

    • Abstract: The interaction between shock waves and the tip clearance flow in a transonic compressor rotor has important effects on the tip clearance flow and the rotor aerodynamic performance. In this paper, two transonic rotors with a high pressure ratio are selected to study the tip flow, one of which has one normal shock wave at the blade tip and the other has two shock waves (an oblique shock wave and a normal shock wave) at the tip. The two rotors have the same meridional flow channel, design point flow rate, pressure ratio, and rotation speed to focus on the influence caused by the effect of the shock wave structure. The numerical results for the flow fields show the following conclusions. The strength of the two shock waves at the blade tip is weaker than that of one normal shock, and the former two shock waves are less stable than the latter. Therefore, with increasing tip clearance, the efficiency, pressure ratio, and stall margin of the rotor with the two shock waves decrease more rapidly. The static pressure difference between the pressure and suction sides of the tip clearance is the only driving factor of the tip clearance leakage flow, and the leakage flow depends on the local pressure difference and the secondary leakage caused by adjacent blades. The movement speed of the annular wall is less than that of the leakage flow, which has a minor blocking effect on the tip clearance leakage flow. The change in tip clearance has little effect on the chordal distribution of the static pressure difference and leakage flow rate per unit area, so the total leakage flow varies linearly with the tip clearance size.
      PubDate: Mon, 20 Feb 2023 02:50:00 +000
  • Aerodynamic Load Reduction on a Supercritical Airfoil Using Tilted

    • Abstract: Microjets arranged on the wing surfaces of civil transport aircraft have been shown to have great potential in suppressing high-frequency gust loads. This paper presents a study of aerodynamic load reduction on a supercritical airfoil using tilted microjets by solving the Reynolds-averaged Navier-Stokes (RANS) equations. The numerical method was first validated against the experimental and previous numerical data. Afterward, the subsonic and transonic flowfields around the supercritical airfoil were simulated with various angled microjets. The results show that both the lift reduction and the power efficiencies significantly increase as the blowing direction shifts downstream to upstream. The movement and weakening of the shock due to the jet are observed at in transonic flow, resulting in a drag reduction compared to the baseline airfoil. However, the transient subsonic results revealed that the upstream jet induces a strong vortex shedding, which is suppressed in transonic flows. During jet deployment, there are three distinct phases: time lag, vortex rolling-up, and rebalancing, in that order. Once it reaches the trailing edge in subsonic flows, the starting vortex rapidly modifies the load and induced a strong roll-up vortex from the pressure surface. Nevertheless, in transonic flow, the rebalancing stage contributes to a greater reduction in lift due to the additional shock movement and weakening effect.
      PubDate: Sat, 18 Feb 2023 03:05:02 +000
  • Investigation of Aeroelasticity Effect on Missile Separation from the
           Internal Bay

    • Abstract: There is a strong aerodynamic interference when launching the missile in the embedded mode. During the separation process, the carrier aircraft safety may be threatened due to large slenderness ratio, low structural stiffness, and aeroelasticity effects of the missile. The present study simulates missile separation in the presence of the aeroelasticity effects based on the computational fluid dynamics (CFD), rigid body dynamics (RBD), and computational structure dynamics (CSD) coupling method. A hybrid dynamic grid method consisting of the mixed overset unstructured grid and deformation grid is utilized. In order to verify the accuracy of the coupled numerical method, store separation from a wing and AGARD 445.6 wing flutter are first simulated as two standard test cases. The verification results imply that the present coupled numerical method is reliable and capable in simulation of the aeroelastic effect in missile separation. The influence of aeroelasticity on the separation trajectory of a missile from the internal bay is systematically studied at different states. Numerical results show that aeroelasticity substantially affects the missile angular displacement, while it has a slight impact on the linear displacement of the center of mass. Mach number and flight altitude are two important flight parameters that characterize the aeroelasticity effect on missile separation from the internal bay.
      PubDate: Thu, 16 Feb 2023 14:35:00 +000
  • Improved HLLL Lattice Basis Reduction Algorithm to Solve GNSS Integer

    • Abstract: Recently, lattice theory has been widely used for integer ambiguity resolution in the Global Navigation Satellite System (GNSS). When using lattice theory to deal with integer ambiguity, we need to reduce the correlation between lattice bases to ensure the efficiency of the solution. Lattice reduction is divided into scale reduction and basis vector exchange. The scale reduction has no direct impact on the subsequent search efficiency, while the basis vector exchange directly impacts the search efficiency. Hence, Lenstra-Lenstra-Lovász (LLL) is applied in the ambiguity resolution to improve the efficiency. And based on Householder transformation, the HLLL improved method is also used. Moreover, to improve the calculation speed further, a Pivoting Householder LLL (PHLLL) method based on Householder orthogonal transformation and rotation sorting is proposed here. The idea of PHLLL method is as follows: First, a sort matrix is introduced into the lattice basis reduction process to sort the original matrix. Then, the sorted matrix is used for Householder transformation. After transformation, it needs to be sorted again, until the diagonal elements in the matrix meet the ascending order. In addition, when using the Householder image operator for orthogonalization, the old column norm is modified to obtain a new norm, reducing the number of column norm calculations. Compared with the LLL reduction algorithm and HLLL reduction algorithm, the experimental results show that the PHLLL algorithm has higher reduction efficiency and effectiveness. The theoretical superiority of the algorithm is proved.
      PubDate: Wed, 15 Feb 2023 14:35:01 +000
  • Characteristics of Flow Development and Boiling Transitions in the Liquid
           Oxygen Chill-Down Process in a Straight Horizontal Exit-Contracted Pipe

    • Abstract: Liquid oxygen chill-down in a straight horizontal pipe was studied experimentally. The effect of the entrance corner was excluded, and much denser wall temperature sensors along the pipe have been set compared to the present studies. In this way, the chill-down process, as well as the development of the flow pattern, has been drawn for every test. As a result, the mechanism of LO2 chill-down would be obtained for various pressure sections. For cases with stable pressure below 1.25 MPa, liquid rewetting in the pipe is controlled by the propagation of quenching fronts. For cases with a higher pressure, liquid rewetting in the second half of the pipe is controlled by the sudden liquid fill-in. Based on the transition points obtained, heat transfer coefficients on the Leidenfrost point and critical heat flux have been correlated for various pressure sections using new approaches. Conclusions show that the correlation equations are dependent on the chill-down mechanisms.
      PubDate: Tue, 07 Feb 2023 07:50:01 +000
  • Multi-UAV Search and Rescue with Enhanced A Algorithm Path Planning in 3D

    • Abstract: The unmanned aerial vehicles (UAV) are now widely used in search and rescue (SAR) missions to locate casualties and survey terrain. To solve the problem of long calculation time and large memory usage of the UAV obstacle-avoidance path-planning algorithm in cooperative tasks, this paper proposes a method that combines the A algorithm and the task allocation algorithm to achieve a faster and more effective path-planning method. First, the environment is displayed in the form of a grid. Then, the enhanced algorithm divides the task area for UAVs. Finally, each UAV performs SAR path planning in the mission area. The tasks of mapping the environment and searching for target points by UAV swarms are discussed in this study. Our research enhances A algorithms for generating the shortest collision-free paths for drone swarms. Further, we evaluate the algorithm via simulating the task assignment algorithm and path-planning algorithm of a 3D map and 2D map. Compared with the traditional A algorithm, the results demonstrate that the enhanced algorithm is effective in the scenario.
      PubDate: Mon, 06 Feb 2023 07:05:01 +000
  • Kriging-Based Space Exploration Global Optimization Method in Aerodynamic

    • Abstract: For complicated aerodynamic design problems, the efficient global optimization method suffered from the defect of the incorrect portrayal of the design space, resulting in bad global convergence and efficiency performance. To this end, a Kriging-based global optimization method, named the Kriging-based space exploration method (KSE), was proposed in this paper. It selected multiple promising local minima and classified them into partially and fully explored minima in terms of the fitting quality of the surrogate model. Then, the partially explored minima would be furtherly exploited. During the local search, an enhanced trust-region method was adopted to make deep exploitation. By combining local and global searches, the proposed method could improve the fitting quality of the surrogate model and the optimization efficiency. The KSE was compared to other global surrogate-based optimization methods on 12 bound-constrained testing functions with 2 to 16 design variables and 2 aerodynamic optimization problems with 24 to 77 design variables. The results indicated that the KSE generally took fewer function evaluations to find the global optima or reach the target value in most test problems, holding better efficiency and robustness.
      PubDate: Thu, 02 Feb 2023 12:35:00 +000
  • Nonlinear Dynamic Responses of a Rotor-Bearing System with Eccentric
           Squeeze Film Dampers

    • Abstract: A squeeze film damper (SFD) is a commonly used component in aeroengine support structures. However, eccentric SFDs are often employed in practical applications. Existing research in this field has mainly focused on simple rotor models and frequency-domain solution techniques. In this study, a rotor system tester with and without an eccentric SFD was built, and a simulation model based on the finite element method and fixed interface modal synthesis method was proposed. Then, the nonlinear dynamic response of the rotor system during run-up and run-down was studied based on the tester and simulation model. The results show that an eccentric SFD affords zero frequency and a series of double frequencies in the rotor system response. An eccentric SFD may cause the increase of the critical speed, amplitude jump, and displacement amplitude oscillation of the rotor system during run-up/run-down. Additionally, it may cause the acceleration response at the mounting bracket to significantly increase when the rotor system is suddenly accelerated.
      PubDate: Mon, 30 Jan 2023 11:50:04 +000
  • A LEO Satellite Handover Strategy Based on Graph and Multiobjective
           Multiagent Path Finding

    • Abstract: Low earth orbit (LEO) satellite network can provide services to users anywhere on the earth. However, the high-speed mobility of satellites leads to a dynamic environment, which brings challenges for handover and network performance optimization, especially in the scenario of multiuser using the networks meanwhile. In this paper, we exploit multiple directed graphs to model the handover process for multiuser. The nodes in a graph represent the satellites that the corresponding user may choose to access. The edges represent the possible handovers between adjacent timestamps. The path from the start node to the end node in each graph is the handover strategy of the corresponding user, and the path length is the reward that the user can get. Therefore, the handover strategy problem is transformed into a path planning problem. To minimize the average handover times, maximize the average received power, and minimize the average number of conflicts, we propose a novel handover strategy based on multiobjective multiagent path finding (MOMAPF). The simulated handover experiment on Starlink successfully derives the Pareto-optimal solution set, which corroborates the effectiveness of the proposed handover strategy. The results also show that the proposed strategy has better comprehensive performance than other strategies.
      PubDate: Mon, 30 Jan 2023 09:05:01 +000
  • Simplified Mixing Rules for Calculating Transport Coefficients of
           High-Temperature Air

    • Abstract: The transport process of high-temperature air is vital in aerospace fields and has attracted increased attention in recent years. In this paper, an adequate study of factors affecting transport coefficients for high-temperature air is conducted. The results of a different-species model at different pressures and temperatures show that the 9-species air model is applicable to calculate the viscosity and translational thermal conductivity coefficients before significant ionization occurs. Based on the Chapman-Enskog method, simplified mixing rules for calculating viscosity and translational thermal conductivity coefficients of high-temperature air are developed by omitting unimportant matrix elements and assuming the reduced collision integral ratio to a reasonable constant value. The diagonal elements’ magnitude of the transport matrix indicates that collision related to the electrons has a little impact on viscosity but has a great influence on translational thermal conductivity. New simplified mixing rules can accurately calculate the viscosity and translational thermal conductivity coefficients of high-temperature air when dissociation or weak ionization occurs. The improved mixing rules are obviously more accurate than the Wilke mixing rule.
      PubDate: Fri, 27 Jan 2023 07:50:01 +000
  • Damage Initiation Analysis of a Tension Stiffened Composite PRSEUS Panel
           Based on Modified Hashin Criteria

    • Abstract: In this study, a damaged three-stringer PRSEUS panel simulating a midbay-to-midbay damage scenario was modelled in Abaqus and analyzed under tension. Moreover, employing the Abaqus built-in Hashin failure criteria verified the reliability of the criteria in predicting damage initiation with great accuracy. Further, these criteria were implemented via UMAT to investigate the effect of shear stress on the analysis, indicating that manipulating the coefficient of shear stress contribution led to a significant enhancement in analysis accuracy. Lastly, the same procedure was followed in the analysis of a repaired three-stringer panel, validating once again the adequacy of the adopted approach and simultaneously highlighting the efficiency of the repair technique in restoring load carrying of the PRSEUS panel. This study may provide a dependable reference presenting a simplified and significantly less computationally demanding approach for damage analysis composite structures and their repair, in addition to further applying these techniques to access the damage-arresting capabilities of these structures.
      PubDate: Mon, 23 Jan 2023 07:50:02 +000
  • High Cycle Fatigue Life Prediction of Single-Crystal Specimen Based on TCD
           Method and Crystal Plasticity Theory

    • Abstract: This paper performs a comprehensive investigation on the high cycle fatigue (HCF) life prediction of turbine blade with film cooling holes. The modified theory of critical distance (MTCD) method is proposed to estimate the fatigue life of the specimen considering the notch sensitivity coefficient and multiaxial stress effect. Then, two types of specimens were designed with regard to the single-hole and multihole conditions. Afterwards, the dangerous path and fatigue life of the two specimens were achieved implementing the MTCD method. Then, the experiments and failure analysis were carried out. The results show that the stress concentration and multiaxial stress resulting from the film cooling holes are the primary reasons that the cracks originated. Meanwhile, the dangerous path of the single-hole specimen is quite different from the multihole specimen due to the interhole interference. Finally, most of the calculated fatigue life is within the twice error band of the tested life.
      PubDate: Thu, 19 Jan 2023 14:20:00 +000
  • S2 Stream Surface Approximation Approach for Quasi Three-Dimensional
           Turbine Time-Marching Design Method

    • Abstract: A fast and reliable turbine design method is necessary in aeroengine development practice. As Q3D time-marching method iteration process can be time consuming and unstable, a novel S2 stream surface approximation approach coupled with flow tangential condition is proposed to reduce the computation requirement. The surface approximation uses a quadratic function of axial coordinate to formulate distribution of circumferential coordinate . The flow tangential condition inherently represents inviscid blade force effect, and the formulation of inviscid blade force is not needed. A corresponding personal Q3D turbine computer code was developed, which was suitable for both design and analysis applications. The Q3D design method solves Euler’s equation through third-order Godunov’s scheme with TVD property in finite volume method. Semi-implicit Crank-Nicolson’s temporal scheme is implemented. Profile, secondary, and tip clearance energy loss models are added to predict viscous losses. Blade row exit swirl is required as the convergence target for Q3D design. A two-stage turbine and a single-stage high-pressure turbine were designed and analyzed by the Q3D method. Viscous 3D CFD was utilized to check design performances. The results showed that the Q3D method could finish a design case within 1 min. At design point, Q3D mass flow rate error was no more than 1.25%, expansion ratio error was no less than -0.022, and isentropic efficiency error was no more than 0.37 percentage points. The Q3D design method is fast and accurate. The stream surface approximation approach is suitable for Q3D design and analysis.
      PubDate: Tue, 17 Jan 2023 10:35:01 +000
  • Autonomous Maneuver Decision of UCAV Air Combat Based on Double Deep Q
           Network Algorithm and Stochastic Game Theory

    • Abstract: Aiming at the problem that unmanned combat aerial vehicle (UCAV) is difficult to quickly and accurately perceive situation information and make maneuvering decision autonomously in modern air combat, which is easily affected by complex factors, a maneuvering decision algorithm of UCAV combined with deep reinforcement learning and game theory is proposed in this paper. Firstly, through the UCAV dynamics model and maneuver library, a reasonable air combat situation assessment model and advantage reward function are established, and the sample data of situation assessment indicators are constructed using the structure entropy weight method. Secondly, the convolutional neural network (CNN) is used to process the high-dimensional continuous situation features of UCAV in air combat, eliminate the correlation and redundancy between situation features, and train the neural network to approximate the action-value function. Then, the double deep Q network (DDQN) algorithm in reinforcement learning (RL) is introduced to train the agent by the interaction with the environment and combined with Minimax algorithm in stochastic game theory to solve the optimal value function in each specific state, and the optimal maneuver decision of UCAV is obtained. Air combat simulation results show that UCAV can choose maneuvers autonomously under different situations and occupy a dominant position quickly by this method, which greatly improves the combat effectiveness of UCAV.
      PubDate: Mon, 16 Jan 2023 11:35:01 +000
  • An Intelligent Algorithm for Aerodynamic Parameters Calibration of Wind
           Tunnel Experiment at a High Angle of Attack

    • Abstract: In this paper, an intelligent algorithm for the aerodynamic parameter calibration of wind tunnel experiments of advanced layout aircraft at a high angle of attack is proposed. The proposed algorithm is based on a homologous comparison and tuning algorithm, and it can effectively improve the accuracy of the wind tunnel experiment model. First, based on the analysis of large oscillation wind tunnel experimental data of an advanced layout scaled aircraft, the high angle of attack wind tunnel experimental model composed of static derivative, dynamic derivative, and rotating balance derivative is established. Second, to improve the accuracy of the wind tunnel experimental model effectively, the idea of combing layered calibration and intelligent algorithm for high angle of attack homologous comparison correction is proposed. The proposed method solves the problems of complex structure, a large amount of data, and poor accuracy in homologous comparison of high angle of attack aerodynamic models of advanced layout aircraft. Finally, the homologous comparison interface software is designed based on MATLAB GUI, which integrates the proposed methods and ideas and realizes effective adjustment of aerodynamic parameters of high angle of attack simulation flight wind tunnel test of an advanced layout aircraft. This study provides a reliable engineering and technical means for subsequent high angle of attack flight test verification of the advanced layout aircraft.
      PubDate: Sat, 07 Jan 2023 05:20:01 +000
  • Closed-Loop Fault Diagnosis of SDR Using Gap Metric, PCA, and
           Kalman’s Principle

    • Abstract: The measurement of the pressure in the gas generator (GG) plays a decisive role in the closed-loop regulation of the gas flow in a solid ducted rocket ramjet (SDR). Therefore, the fault detection and isolation (FDI) of the pressure sensors is particularly significant. Especially in the GG with double pressure feedback, there are issues such as less available data and sensor fault transmission, which make the FDI more difficult. In this paper, for the GG with double pressure feedback, firstly, the “Consistency Index” was constructed based on the principal component analysis (PCA) algorithm, which made it easier to evaluate the consistency of the measured values. Secondly, based on Kalman’s principle, the redundancy information of the system was used to estimate the pressure in the GG. Finally, the gap metric between the measured pressure and the estimated pressure was employed to characterize the health of the sensors. Compared with the MWPCA algorithm, it was shown that our proposed algorithm was more accurate in fault diagnosis and could avoid the problem of missing alarm when two sensors had consistent faults, which would provide strong support for the safe operation of the SDR and could further promote its application in long-endurance aircrafts.
      PubDate: Thu, 05 Jan 2023 13:50:00 +000
  • Computational Optimal Impact Angle Control Guidance Laws Weighted by
           Arbitrary Functions

    • Abstract: This paper presents a computational impact angle control guidance law based on the energy cost weighted by arbitrary functions in order to shape the acceleration command as desired. The optimal guidance problem is established in the impact angle frame and is solved by the Gauss orthogonal collocation method. The proposed guidance law is formulated from the generalized optimal control framework, thus a new guidance law that allows achieving a specific guidance goal can be easily obtained in the way of devising a proper weighting function (smooth, piecewise, nonsmooth, or even discontinuous). This property provides more degrees of freedom in the guidance law design to accomplish a specified guidance objective. A hardware experiment is conducted to evaluate the real-time computational capacity of the proposed computational guidance law. Illustrative examples with several types of weighting functions, including smooth, piecewise, nonsmooth, and discontinuous functions, are provided to demonstrate the advantages and capacity of the proposed guidance law.
      PubDate: Thu, 05 Jan 2023 13:35:01 +000
  • A Decision-Making Method for Distributed Unmanned Aerial Vehicle Swarm
           considering Attack Constraints in the Cooperative Strike Phase

    • Abstract: In view of the growing military forces of various countries, unmanned aerial vehicle (UAV) swarms, as a new type of weapon, are gradually attracting the attention of more and more countries. Decision-making, as the core link in its application, has also become the focus of research in these countries. In this work, the distributed UAV swarm cooperative strike decision-making problems are separated from the distributed UAV swarm cooperative search strike decision-making problems, and the distributed UAV swarm cooperative strike multiobjective decision-making model is established, with the relevant constraints clarified. Besides, according to the analysis of the motion characteristics of UAV and the speed requirements of the distributed UAV swarm cooperative strike decision, an arc tangent trajectory planning method, conforming to the motion characteristics of UAV, is proposed. Moreover, a distributed cooperative strike decision-making method, based on the idea of “campaign endorsement and invitation cooperation,” is put forward, with the effectiveness and superiority validated by simulation experiments.
      PubDate: Wed, 04 Jan 2023 14:05:01 +000
  • A Preliminary Research on Combustion Characteristics of a Novel-Type
           Scramjet Combustor

    • Abstract: In this work, a new configuration of strut-based scramjet is proposed, and a series of simulations are conducted to investigate its possibility of practical application. The simulation results are verified via the classical DLR ramjet and an experiment conducted on the connected pipe facility. The inlet area () and air intake height () of the combustor are varied independently to investigate their performance. The results indicate that the flow field and shock wave structure of such engine reveal similar characteristics as the classical DLR engine, and the variation in engine geometry can significantly affect its combustion characteristics. Moreover, the combustion efficiency could be enhanced by 2% as the varied from 900π mm2 to 1100π mm2; increasing the air intake path () to 12 mm can increase the combustion efficiency by 25%. In general, the present work proposes a new geometry of the scramjet combustor; this combustor has possibility of practical application, but a further and detailed investigation is still needed.
      PubDate: Fri, 30 Dec 2022 07:20:01 +000
  • A Midcourse Guidance Method Combined with Trajectory Prediction for
           Antinear-Space-Gliding Vehicles

    • Abstract: Near-space-gliding vehicles have variable maneuver modes and dramatic changes in their ballistic parameters, which lead to a need to accurately predict an intercept point based on predictions of their trajectories. First, a trajectory prediction method builds a set of time-varying maneuver models based on flight missions combined with an adaptive grid to infer maneuver modes. An interactive multiple-model method of variable structure is proposed to identify the characteristics of the maneuver mode by introducing a fading factor and the modified Markov probability transfer matrix and then predict the trajectory through numerical integration. In the midcourse guidance method, the prediction of the target trajectory is introduced, and the zero-control interception manifold with intersection angle constraints is designed as the midcourse guidance terminal constraint. For the calculation of the starting time of the boost phase, the optimization solution satisfying the remaining flight time constraint is realized based on the Newton-Raphson iterative method. The analytical expression of a guidance command based on zero-error-miss/zero-error-velocity is established on the basis of the optimal control theory to provide an optimal flight path guiding an NSGV fly toward a point of interception. The simulation results show that the trajectory-prediction method has high prediction accuracy and strong convergency for typical maneuver modes, and the proposed midcourse guidance algorithm meets the requirements of the zero-effort intercept manifold with the intersection angle constraints, which is of important theoretical significance and acts as a reference value for intercepting high-velocity maneuver targets.
      PubDate: Wed, 28 Dec 2022 08:20:01 +000
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