Article of the Year 2020
Processing Technology Based on Radar Signal Design and ClassificationRead the full article
International Journal of Aerospace Engineering serves the international aerospace engineering community through the dissemination of scientific knowledge on practical engineering and design methodologies pertaining to aircraft and space vehicles.
Chief Editor, Professor Zhao, is based at the University of Canterbury and his research interests include applying theoretical, numerical and experimental approaches to study combustion instability, thermoacoustics and aerodynamics.
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Envelope-Based Variable-Gain Control Strategy for Vibration Suppression of Solar Array Using Reaction Wheel Actuator
The orbital operation of spacecraft can excite the long-drawn and low-frequency vibration of the solar array, which is prone to affecting the task execution of the system. To address this issue, an envelope-based variable-gain control strategy is proposed to suppress vibration of the solar array using the reaction wheel (RW) actuator. The RW actuator is individually mounted on the solar array to provide reaction torque through the speed change of its rotor. The governing equation of motion of the solar array actuated by a RW actuator is deduced with the state space representation. The control relation between the measured bending moment and the rotational speed of the RW actuator with the constant-gain coefficient is firstly developed and demonstrated in numerical simulation. Changing the gain coefficient to be inversely proportional to the envelope function of vibration, a variable-gain control strategy is proposed to improve the damping effect of the RW actuator. Simulation results show that the vibration suppression performance of the RW actuator is improved compared to the constant-gain control. As the actual on-orbit natural frequency of the solar array is not always exactly known, the robustness of the control system is analyzed for the deviation between the estimated and the actual natural frequency values. The proposed variable-gain control is also experimentally verified using a simplified elastic plate model. Experimental results indicate that the vibration attenuation time is decreased to 29.1% and 50.22% compared to the uncontrolled and the constant-gain controlled states, respectively.
Robust Integrated Guidance and Control Design for Angle Penetration Attack of Multimissiles
Angle penetration attack ability plays a more and more important role for missiles in modern warfare, and the traditional separate guidance and control system design problem is the key to restrict the improvement of time-sensitive attack and cooperative attack ability of multimissiles. Firstly, the deviation control strategy of line-of-sight angle and attack angle is put forward in this paper, and the integrated guidance and control system model with impact angle constraint is established, according to the characteristics of angle penetration attack. Then, an integrated guidance and control controller for angle penetration attack is designed by using adaptive dynamic surface control, with the dynamic constraints, nonlinear input saturation, and terminal line-of-sight and attack angle constraints concerned. In order to ensure the robustness of the system, nonlinear disturbance observers are introduced to estimate the uncertainty of the system model. Finally, the stability of the integrated design method is proven based on the Lyapunov theory. Simulation results verify the effectiveness of the integrated guidance and control design method proposed in this paper in multimissile angle penetration attack.
Thermal Analysis and Rigid-Flexible Coupling Dynamics of a Satellite with Membrane Antenna
In this paper, the thermal analysis of a membrane antenna structure is performed, and then, the rigid-flexible coupling dynamic modeling and control of the membrane-antenna-satellite system are studied with the thermal stress considered. The thermal analysis model of the membrane antenna structure is derived based on the finite element method by discretizing the structure into 1D and 2D thermal elements. Considering the thermal stress, the vibration modes of the membrane antenna structure are obtained, and the rigid-flexible coupling dynamic model of the membrane-antenna-satellite system is derived based on the hybrid coordinate method. To reduce the vibration of the membrane antenna structure caused by the attitude maneuver, the control command is designed based on the component synthesis vibration suppression (CSVS) method. Simulation results show that the dynamic properties of the membrane antenna structure are affected significantly by the space thermal environment, the vibration of the membrane antenna structure can be suppressed effectively by the presented CSVS controller, and the accuracy of the attitude maneuver will be improved significantly by the proposed control strategy.
Study of the Mechanical Properties of a CMDB Propellant Over a Wide Range of Strain Rates Using a Group Interaction Model
Composite modified double base (CMDB) propellants are heterogeneous propellants in which properties are significantly improved by adding solid particles into the polymer matrix. A molecular group interaction model that can predict the mechanical properties of polymers through a molecular structure is used to predict the viscoelastic behavior of the CMDB propellant. Considering that the addition of solid particles will improve the crosslinking degree between polymer molecules and reduce its secondary loss peak, the input parameters of the model are modified through dynamic mechanical analysis (DMA) experimental data. By introducing the strain rate into the expression of model glass transition temperature, the mechanical properties of propellant over a wide strain range ( s-1 ~ 3000 s-1) are obtained. The reliability of the model is verified by comparison with uniaxial compression test data. By modifying the input parameters of the model, the effects of different mass ratios of nitrocellulose (NC)/nitroglycerin (NG) on the mechanical properties of the CMDB propellant were analyzed. The results show that the glass transition loss increases with increasing mass ratio of NC/NG, while Young’s modulus and yield stress decrease.
Enhancing Short-Term Prediction of BDS-3 Satellite Clock Bias Based with BSO Optimized BP Neural Network
The satellite clock bias (SCB) prediction plays an important role in high-accuracy and real-time navigation and positioning. When predicting the SCB, the performance of the BP neural network is affected by the local optimum due to inaccurate initial parameters. Therefore, we propose an improved BP neural network based on the beetle swarm optimization (BSO-BP) algorithm to improve the performance of SCB prediction in third-generation Beidou satellite navigation system (BDS-3). The proposed model takes advantage of group learning strategy to optimize the initialization parameters of the BP neural network and obtains globally optimized parameters. In order to verify the proposed BSO-BP model, 15 BDS satellites are analyzed in terms of prediction accuracy and stability of SCB. The experimental results show that when predicting 1 hour SCB based on a 12 hours SCB data, the prediction accuracy of the BSO-BP model is the best, with an average accuracy of 0.064 ns. As compared with the LP, QP, and GM models, the average prediction accuracy of the proposed BSO-BP model increases by about 72.6%, 43.4%, and 86%, respectively. As the prediction time increases, the influence of the inaccurate initial parameters on SCB prediction gradually decreases, and the prediction accuracy improves. The proposed BSO-BP model has the best accuracy and stability when predicting the 1 h SCB based on the same data. The prediction stability of the proposed BSO-BP model improves by more than 36% as compared with LP, QP, and GM models. In addition, the prediction accuracies of PHM clock and Rb-II clock improved by more than 47%, as compared with that of the Rb clock. Therefore, the overall performance of the atomic clock based on BDS-3 is better than BDS-2. The positioning accuracy of the BSO-BP model can reach the centimeter level in east, north, and up directions.
Pretension Design and Analysis of Deployable Mesh Antenna considering the Effect of Gravity
The difference between the space and the earth environment has significantly influenced the shape accuracy of the antenna reflector surface. With the increasing demand for the aperture of the antenna reflector, gravity has become one of the main factors that restrict the accuracy. In this paper, a new method for pretension design considering the effect of gravity is proposed. The design surface can be well restored to the ideal surface in orbit. Meanwhile, this method can avoid flipping antenna reflectors or extensive experiments for modification during ground adjustment. Then, the feasibility and effectiveness of the design method are validated by several numerical simulations. Moreover, the results are compared with the previous method and the differences have been discussed in detail. Finally, the effects of cable radius, cable length, and elastic modulus of the mesh reflector have been researched, respectively.