Table of Content

    25 December 2010, Volume 30 Issue 6 Previous Issue    Next Issue
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    Dynamics Modeling and Low Rate Control ofGimbal Servo System for Single Gimbal Control Moment Gyro
    JIN Lei, XU Shi-Jie
    2010, 30 (6):  1-10. 
    Abstract ( 3734 )   PDF (531KB) ( 2706 )   Save
    In order to ensure the high precision of output torque, the precise dynamics modeling and control of gimbal servo system were studied. By thorough dynamics analysis of single gimbal control moment gyro (SGCMG) mounted on the spacecraft, the dynamic model of gimbal servo system was established, taking into account the largest disturbing torque along the gimbal axis resulted from rotor imbalance and the friction torque. For the gimbal servo system using a sinusoidal permanent magnetic synchronous motor (PMSM), the inner and outer loop controllers were both designed based on the active disturbance rejection control (ADRC) theory. The simulation results demonstrate that under the assumption that the high frequency disturbing torque resulted from rotor imbalance is ignored, the modeled and unmodeled disturbance existing in both loops were estimated and compensated exactly using the ADRC controller, so that the high precision control of gimbal servo system was ensured. The results also show the effect level of the rotor imbalance on gimbal control precision.
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    Nonlinear Feed Forward Control on Attitude andOrbital Coupling Model  for Spacecraft
    TIE Yu-Jia, YUE Xiao-Kui, CAO Jing
    2010, 30 (6):  11-16. 
    Abstract ( 4954 )   PDF (322KB) ( 2281 )   Save
    Precise relative orbit and attitude model play a significant role in the spacecrafts formation flying, rendezvous and docking. Nevertheless, the independent relative orbital model can't meet the high precision requirements. Based on the nonlinear relative motion dynamics equations and attitude kinematics equations described by modified Redrigues parameters (MRPs), a relative dynamic model of 6 DOF was developed. The accuracy of the model is  guaranteed with couplings and nonlinear terms′supporting. Nonlinear feed forward control law was designed for the coupled nonlinear dynamic model, whose close loop system was proved to be global asymptotic stable by Lyapunov direct method. The numerical simulations results verify the effectiveness of the model and control law.
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    Hovering Method at Any Selected Position over Space Target on Elliptical Orbit
    ZHU Ya-Wen, YAN Ye
    2010, 30 (6):  17-23. 
    Abstract ( 3680 )   PDF (364KB) ( 2816 )   Save
    By implementing a continuous control acceleration, the relative position of a mission satellite to a target satellite can keep fixed during the mission. So the hovering flying at any selected position over a satellite on elliptical orbit is carried out. The relative motion was studied and the gravitation between the two satellites was researched. The formulae for radial, tangential and normal control acceleration required during the hovering flying mission were put forward. The numerical simulation for typical mission was conducted, and the energy requirements of the hovering spacecraft for different tasks were compared and analyzed. The results show that it is feasible to hover over a special target satellite within a period of time.
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    CEI based Real time Orbit Determination of Spacecraft Rendezvous and Docking in the Course of Long Distance Navigation
    LI Xiao-Jie, DU Lan, HUANG Jin, PAN Ling
    2010, 30 (6):  24-30. 
    Abstract ( 2986 )   PDF (333KB) ( 1851 )   Save
    Connected element interferometry (CEI) is a passive angular tracking method with the characteristic of short baselines, flexible network distribution and nearly real time processing. It can make realtime and precise orbit determination for spacecraft rendezvous and docking.CEI based real time orbit determination in the course of long distance navigation of spacecraft rendezvous and docking was discussed, and the method of absolute filter was adopted. The simulation results indicat that the method of fixing integer ambiguity after the filter is stable, and can improve the orbit precision. The relative position precision can reach the magnitude of 10m, and the relative velocity precision reaches the magnitude of 1cm per second.
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    In orbit Estimation of Satellite inertial matrix using STLS
    LIN Jia-Wei, WANG Ping
    2010, 30 (6):  31-38. 
    Abstract ( 5600 )   PDF (384KB) ( 2964 )   Save
    Dynamics equations of inertial matrix estimation were deduced. The structured total least norm (STLN) algorithm was used to estimate the parameters. Theoretical analysis shows that the STLS solution is maximum likelihood estimate when the sensor noise is Gaussian. This method has two advantages over existing methods: sensor noise is considered and the consistency of the estimate is proved.
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    Guidance for Dynamic Obstacle Avoidance of Autonomous Rendezvous and Docking with Non-Cooperative Target
    SONG Shen-Min, ZHANG Da-Wei, PEI Run
    2010, 30 (6):  39-48. 
    Abstract ( 4433 )   PDF (558KB) ( 2528 )   Save
    Firstly, the relative motion state equations were described in line of sight coordinate frame. And the artificial potential function guidance was used for autonomous rendezvous and docking  with a non-cooperative target spacecraft and dynamic obstacle avoidance missions. Then, mission of autonomous rendezvous and docking with the non-cooperative target was accomplished and dynamic obstacle avoidance was studied by potential function guidance. Secondly, the stability of the method was analyzed and proved by Lyapunov theory, and the effects of two different dynamic obstacle avoidances were studied and discussed. Meanwhile, the capability of potential function guidance was analyzed. Finally, the numerical simulation results based on a precise mathematic model demonstrate the validity and effectiveness of the proposed guidance method.
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    Design and Dynamic Simulation of Hinged Deployable Configuration Spacecraft
    MA Shang-Jun, LIU Geng, LUO Hao
    2010, 30 (6):  49-56. 
    Abstract ( 3858 )   PDF (535KB) ( 2819 )   Save
    Based on modular design idea of the spacecraft structure, a hinged deployable configuration for the spacecraft was designed. The virtual prototyping model of modular body and solar panels was established with virtual prototyping technology. And the influence of three deployment sequences of modular body and solar panels on attitude of the spacecraft in the weightless space environment were analyzed, including the modular body and solar panels deployed simultaneously, the modular body deployed after the solar panels, and the solar panels deployed after  the modular body.  Meanwhile, the influences of different torsion spring parameters on attitude angle and deployment time were compared.
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    Radar Data Error-correction Technique Based on Hilbert-Huang Transform
    YU Hui, HU Shao-Lin, LI Ping
    2010, 30 (6):  57-63. 
    Abstract ( 3159 )   PDF (436KB) ( 1941 )   Save
    Radar tracking always causes data errors, but the current error processing algorithms can not satisfy the need of error correction. To esitimate the unknown data errors efficiently and improve the precision of data processing, a residual error diagnosing method was proposed based on Hilbert-Huang transform arithmetic. By the analysis using the obtained intrinsic mode function, the characteristics of residual error were fitted, and the error information were separated accurately. Experiments using the actual radar data show that the method is more effective and practical than others for post-mission high-precision data processing.
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    Applications and Construction of the Structured LDPC Codes in Satellite Navigation System
    JIANG Ming, HE Shan-Bao, DOU Jin-Fang, ZHAO Chun-Ming, WANG Chen
    2010, 30 (6):  64-71. 
    Abstract ( 4793 )   PDF (533KB) ( 2303 )   Save
    The structured low density parity check (LDPC) codes can be described by the base-matrices and lifting factors, which have low encoding/decoding complexity and good coding performance. Compared to the irregular LDPC codes specified in IS-GPS-800, the structured LDPC codes also can be encoded with linear complexity, where the parity bits are connected with dual-diagonal and “a-0-a” pattern. Moreover, it is very convenience for the structured LDPC codes to support the adaptive transmissions with various lengths using different lifting factors and pruning techniques, where the puncturing and shortening patterns can be easily optimized by PEXIT. Based on the construction method considering cycle conditions and ACE spectrums, a simple coding scheme using only one base-matrix was proposed which can support two different lifting factors and achieve various transmission lengths by puncturing and shortening. The simulation result show that the structured LDPC codes with optimized puncturing/shortening pattern achieve considerable performance gain over the irregular LDPC codes in IS-GPS-800.
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    Methods of Mission Analysis, Design and Validation for Lunar Exploration Based on STK
    HUANG Wen-De, XI Xiao-Ning, WANG Wei
    2010, 30 (6):  72-80. 
    Abstract ( 3136 )   PDF (482KB) ( 3560 )   Save
    In order to reduce the cost and improve the research efficiency of lunar exploration during the mission design phase, an approach using STK software was proposed for mission analysis, design and validation. First, trajectory design of the lunar probe was discussed based on differential correction. Then the problems of validating the design result of patched conic technique were analyzed and considerations were listed when using STK for that purpose. Finally, addressing on the inconveniences in STK when it was used to set the lunar point and the motion of lunar rover vehicle, an external file importing method was employed, and the lighting and station coverage of lunar point was analyzed by this method. The simulation results show that the methods proposed can realize efficiently in the mission analysis, design and validation of the lunar exploration.
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    2010, 30 (6):  81-87. 
    Abstract ( 2111 )   PDF (365KB) ( 2056 )   Save
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