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Time filter

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Zhang S.,Harbin Institute of Technology | Zhao Y.,Harbin Institute of Technology | Chen M.,Harbin Institute of Technology | Cao X.,Harbin Institute of Technology | He L.,Shanghai Key Laboratory of Space Intelligent Control Technology
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2011

The reaction wheels play an important role in shaping satellite attitude command. To ensure the reliability of satellite in orbit, the reaction wheels are often overactuated with more than three reaction wheels. Therefore, dynamic control allocation method based on pseudo-inverse method distributing the desired control command among the reaction wheels is proposed. But for controls constrained to operational limits, the pseudo-inverse approach yields admissible control deflections for only a small portion of the set of attainable moments. So a null-space method is used to modify the results. Under the assumption that the attitude changes smoothly when satellite is stabilized, the minimum-torque dynamic control allocation can remove the unexpected signals and reduce noise effect in attitude control by limiting the differences between current value and one-step previous value. In this way, the precision of attitude control system is improved. Finally, the proposed dynamic control allocation method is tested in removing undesired signals and reducing noise effects. The method is proved to be feasible and effective after simulation. Source


Yuan C.-X.,Harbin Institute of Technology | Zhou Z.-X.,Harbin Institute of Technology | Yue F.,Shanghai Key Laboratory of Space Intelligent Control Technology
Proceedings - 2012 5th International Conference on Intelligent Computation Technology and Automation, ICICTA 2012 | Year: 2012

The properties of Terahertz (THz) waves propagation in a bounded plasma slab with high plasma density and high collision frequency are studied in this paper. The method of impedance transformation in multiple dielectrics is used to describe the propagation of THz waves in the plasma layer. The effect of various plasma parameters such as the plasma density, sheet thickness, incident wave frequency and collision frequency on the power transmission, absorption and reflection is investigated. The calculated numerical results show that a THz wave can transmit though a dense and high collision frequency (to the order of 10 12-THz) plasma with reflectionless and absorptionless power. When the change of plasma density leads the plasma frequency to be in the vicinity of the incident THz wave frequency, the plasma can absorb the most THz wave power. The potential applications of these propagation properties are discussed in this paper. © 2012 IEEE. Source


Huang H.,Nanjing University of Aeronautics and Astronautics | Pan M.,Nanjing University of Aeronautics and Astronautics | Lu Z.,Nanjing University of Aeronautics and Astronautics | Lu Z.,Shanghai Key Laboratory of Space Intelligent Control Technology
Chinese Journal of Aeronautics | Year: 2015

Hardware-in-the-loop (HWIL) simulation technology can verify and evaluate the radar by simulating the radio frequency environment in an anechoic chamber. The HWIL simulation technology of wide-band radar targets can accurately generate wide-band radar target echo which stands for the radar target scattering characteristics and pulse modulation of radar transmitting signal. This paper analyzes the wide-band radar target scattering properties first. Since the responses of target are composed of many separate scattering centers, the target scattering characteristic is restructured by scattering centers model. Based on the scattering centers model of wide-band radar target, the wide-band radar target echo modeling and the simulation method are discussed. The wide-band radar target echo is reconstructed in real-time by convoluting the transmitting signal to the target scattering parameters. Using the digital radio frequency memory (DRFM) system, the HWIL simulation of wide-band radar target echo with high accuracy can be actualized. A typical wide-band radar target simulation is taken to demonstrate the preferable simulation effect of the reconstruction method of wide-band radar target echo. Finally, the radar target time-domain echo and high-resolution range profile (HRRP) are given. The results show that the HWIL simulation gives a high-resolution range distribution of wide-band radar target scattering centers. © 2015 The Authors. Source


Cheng Y.,Nanjing University of Aeronautics and Astronautics | Jiang B.,Nanjing University of Aeronautics and Astronautics | Sun J.,Shanghai Aerospace Control Engineering Institute | Sun J.,Shanghai Key Laboratory of Space Intelligent Control Technology | And 2 more authors.
ICIC Express Letters | Year: 2011

This paper is concerned with the design of a robust actuator fault diagnosis and tolerant control scheme for satellite attitude control systems. A bank of sliding mode observers (SMOs) are firstly investigated to detect and isolate single actuator fault for satellite attitude control systems with input disturbance. When an actuator undergoes unknown fault, it is disabled. Under such condition, a novel fault tolerant controller based on sliding mode control method is proposed to keep system safe using the remaining actuators. Simulation results demonstrate the effectiveness of the proposed method for satellite attitude control systems. © 2011 ISSN 1881-803X. Source


Ren J.-D.,Harbin Institute of Technology | Ren J.-D.,Shanghai Aerospace Control Engineering Institute | Ren J.-D.,Shanghai Key Laboratory of Space Intelligent Control Technology | Zeng Q.-S.,Harbin Institute of Technology | And 2 more authors.
Zhongguo Guanxing Jishu Xuebao/Journal of Chinese Inertial Technology | Year: 2016

Long-range autonomous rendezvous is crucial to the precise placemen of geostationary collocation satellites. Based on the analysis of error signal characteristics of relative motion model during large-span remote rendezvous process, the error transfer mechanism is theoretically derived. Then the quantitative analysis model of mean and noise characteristic is proposed for the relative navigation based on an extended Kalman filter (EKF) algorithm. The analysis results show that there exists an optimal process noise level and corresponding optimal filter performance with respect to the determining distance range. The estimation error is positively correlated with the intersection distance, which can be used as the quantitative basis to design a global optimum filter. Besides, it also theoretically provides an approach to quantitatively evaluate the navigation performance of the EKF optimal filter during long-range rendezvous of geostationary orbit. Simulation results demonstrate that the analysis results are correct, and the relative velocity estimation error is 0.005 m/s (1σ), which satisfies the mission requirements of orbit long-range rendezvous. © 2016, Editorial Department of Journal of Chinese Inertial Technology. All right reserved. Source

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