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    25 August 2012, Volume 32 Issue 4 Previous Issue    Next Issue
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    Flexible Spacecraft Attitude stabilization Control Based on Direct Adaptive Algorithm
    LIU Min, XU Shi-Jie, HAN Chao
    2012, 32 (4):  1-7.  doi: 10.3780/j.issn.1000-758X.2012.04.001
    Abstract ( 1898 )   PDF (396KB) ( 1444 )   Save
    An adaptive control strategy based on backstepping control and direct adaptive control was proposed to resolve the flexible spacecraft attitude stabilization control problem. Firstly, the flexible spacecraft was divided into dynamics subsystem and kinematics subsystem, and an ideal reference model was designed. Secondly, under the assumption of small attitude angle, a direct adaptive intermediate control law was designed. Finally, the spacecraft attitude controller was designed by adopting the backstepping control method, and the stability of the close loop control system was proved. Theoretical study and numerical simulation results validate the efficiency of the flexible spacecraft adaptive attitude stabilization controller.
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    Coupled Control of Relative Position and Attitude Based on θ-D Technique for On-orbit Operations
    LI Peng, YUE Xiao-Kui, YUAN Jian-Ping
    2012, 32 (4):  8-14.  doi: 10.3780/j.issn.1000-758X.2012.04.002
    Abstract ( 1901 )   PDF (394KB) ( 1271 )   Save
    For the problems of relative dynamics and control in the onorbit operations such as module replacement, fuel charge and so on, coupled dynamics model of relative orbit and attitude was established to describe the relative motion of two spacecrafts in close range. Orbit perturbation and attitude disturbed torque was used to illustrate the impact of the coupled terms on the model. With the consideration of the nonlinear and time varying of dynamic model based on the state dependent coefficient form,θ-D suboptimal control algorithm was adopted to design the controller of the coupled model of the relative translation and rotation. For the mission of space refuel during the final approach of an uncontrolled rotating satellite, the θ-D method is validated to be capable to realize the synchronization control of the relative orbit and attitude through the numerical simulation, which simplifies the calculation of controller and achieves a comparatively high precision.
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    Simplified Calculating Method of the Sun Radiation Flux for On-orbit Satellite
    LIU Xin, PAN Zeng-Fu
    2012, 32 (4):  15-21.  doi: 10.3780/j.issn.1000-758X.2012.04.003
    Abstract ( 1899 )   PDF (386KB) ( 1650 )   Save
    A simplified method was put forward to solve the problems of too much orbital parameters and complex space geometry during calculating sun radiation flux for on-orbit satellite. A novel calculation coordinates was built based on studying the space geometrical relationship between the satellite, the earth and the sun. In the coordinates, the space position between the satellite, the earth and the sun was re-ruled and the calculation formula of the sun direct radiation flux was deduced. Using the proposed method to calculate the sun radiation flux, the process is simplified. Compared with conventional methods, only 7 parameters need to be calculated and the parameters are decreased by 2/3.
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    Recursive Finite Segment Method Analysis of Flexible Spacecraft Undergoing Large Overall Motions
    LI Wen-Long, YU Zheng-Ning, SHI Peng, ZHAO Yu-Shan
    2012, 32 (4):  22-27.  doi: 10.3780/j.issn.1000-758X.2012.04.004
    Abstract ( 1805 )   PDF (357KB) ( 1518 )   Save
    The number of freedom degree of flexible spacecraft undergoing large overall motions would increase largely if the finite segment method was adopted, so the traditional methods would be inefficient. A more efficient way was proposed by combining the finite segment method and the spatial operator algebra theory. Firstly, the flexible components were divided into several rigid bodies, so the original system turned to be a rigid multi-body with flexible joints. Then, the spatial operator algebra (SOA) theory based recursive kinetic equation of motion was established. Finally,a numerical example of two flexible link manipulators was presented. The simulation results are quite consistent when the problem was solved by the SOA method as well as the Newton Euler method. The computation time indicates that it increases linearly with the number of DOF by spatial operator algebra theory, and much fewer than that of the Newton Euler method. Results confirm the validation and efficiency of this method.
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    Terminal Sliding Mode Control for Attitude Tracking of an Autonomous Airship
    YANG Yue-Neng, WU Jie, ZHENG Wei
    2012, 32 (4):  29-36.  doi: 10.3780/j.issn.1000-758X.2012.04.005
    Abstract ( 1731 )   PDF (354KB) ( 1482 )   Save
    The attitude control system of an autonomous airship is a multi-input multi-output, nonlinear, coupled and uncertain system. A new control scheme based on feedback linearization and terminal sliding mode for attitude tracking control was proposed. Firstly, the mathematical model of the attitude motion of an airship was derived in form of a nonlinear system. Secondly, the nonlinear attitude control system was decoupled into three single-input single-output linear systems based on the differential geometry theory. The attitude tracking control system was designed by using the terminal sliding mode control method, and the stability of the closed loop system was proven by using the Lyapunov theorem. Finally, simulation results demonstrate that the control system tracks the commanded attitude angles precisely despite of model uncertainties, which verifies the effectiveness and robustness of the proposed control scheme.
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    Relative Position and Attitude Determination Between Spacecrafts Based on Bifocal Monocular Vision
    FENG Chun, WU Hong-Tao, QIAO Bing, CHEN Bai
    2012, 32 (4):  37-44.  doi: 10.3780/j.issn.1000-758X.2012.04.006
    Abstract ( 1892 )   PDF (439KB) ( 1599 )   Save
     Firstly, the relative position parameters were computed by using the bifocal imaging algorithm. Then, the relative attitude parameters were calculated by the position parameters which have been obtained. At last, the analytical solution of relative position and attitude parameters was achieved. Under the condition of two different sets of focals, the bifocal depth estimation error was analyzed, the influence factors of precision were pointed out, and the estimation precision of relative position and attitude parameters was discussed. The solution has been validated by using mathematical simulation, and simulation results show that the solution can satisfy the accuracy of relative parameters between spacecrafts and the realtime computation.
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    Disturbance Modeling and Performance Index Evaluation of the Small Control Moment Gyroscope
    ZHANG Yao, JIN Lei, XU Shi-Jie
    2012, 32 (4):  45-53.  doi: 10.3780/j.issn.1000-758X.2012.04.007
    Abstract ( 2033 )   PDF (560KB) ( 1257 )   Save
    Control moment gyro (CMG) is widely used as the actuator for attitude control on satellites recently. To realize high precise pointing capability of a high resolution remote sensing satellite, the disturbance modeling and performance index evaluation of CMG were discussed. Firstly, considering the static and dynamic imbalances of the rotor and installation errors, the small CMG dynamic model was constructed  by means of the theorem of momentum and theorem of angular momentum. The validity of this model was analyzed based on an experience model of a flywheel and testified by numerical simulation. Secondly, a cluster of the CMGs were adopted and the whole satellite dynamic model was derived. To complete the mission of the satellite attitude stabilization control, the reasonable servo control systems of the gimbals and the rotor were selected. Finally, the influences of the CMG disturbances on the attitude precision and satellite stability were analyzed in detail. According to the space mission of the high resolution remote sensing satellite, the constraint condition of the CMG performance index was obtained to meet the imaging requirements of the optical payloads.
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    Compensation for Optical Remote Sensing Image Compression Based on Distortion Sensitivity
    YANG Kai, JIANG Hong-Xu
    2012, 32 (4):  54-61.  doi: 10.3780/j.issn.1000-758X.2012.04.008
    Abstract ( 1781 )   PDF (908KB) ( 1141 )   Save
    High resolution optical remote sensing images are prone to serious local distortion after high compression, whose targets and textures are abundant and complex. Most of the current researches do not focus on subjective image quality, and this will easily lead to over compensation. In order to reduce local distortion, the correlations between SSIM (Structural similarity) component functions and MOS (Mean opinion score) were analyzed on an optical remote sensing compression distortion image database, and a distortion sensitivity model for remote sensing image compression was proposed. Then, this model was utilized to design a compensation approach, and applied to an embedded wavelet image coder. This approach could locate the distortion sensitivity areas and compress the distortion values to reserved space at encoder, and compensate these values into reconstructed image at decoder. Experiment results show that this approach can enhance the visibility and identification of remote sensing objects in the distorted sensitive areas, reduce serious local distortions, and improve the overall image quality.
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    Autonomous Navigation and In-orbit Parameter Calibration for Continuous Low Thrust Spacecraft
    SHI Heng, XU Shi-Jie
    2012, 32 (4):  62-70.  doi: 10.3780/j.issn.1000-758X.2012.04.009
    Abstract ( 1734 )   PDF (571KB) ( 1601 )   Save
    Novel autonomous navigation scheme was proposed for continuous low thrust spacecraft with synchronized calibration on accelerometer, thruster and solar radiation coefficient of the spacecraft. Firstly, by selecting precise attitude measurements and gravity gradient model as reference information,the calibration parameter models was established and the observability was discussed. Secondly, system dynamics and measurement models were developed based on spacecraft celestial navigation methods with observability guarantee. Dual-unscented Kalman filter was then designed to estimate the calibration parameters and navigation system states in an error-robust and integrated manner. The proposed method has directly reduced the navigation model errors through in-orbit parameter calibration, making it preferable in feasibility and effectiveness.  
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    Numerical Simulation Analysis of Space Plasma Detector Based on SIMION
    KONG Ling-Gao, ZHANG Ai-Bing, WANG Shi-Jin, SUN Yue-Qiang, ZHENG Xiang-Zhi, DONG Yong-Jin
    2012, 32 (4):  71-76.  doi: 10.3780/j.issn.1000-758X.2012.04.010
    Abstract ( 2182 )   PDF (381KB) ( 1246 )   Save
    The space plasma detector is a kind of cylindrical electrostatic analyzer with the field of view larger than 320° and the capability of measuring the plasma of 10eV~30keV. The basic parameters of the plasma detector, such as the electrostatic analyzer factor, energy resolution and the relationship between the deflection factor and the deflection angle, were simulated by the software SIMION. The particle source for the simulation was constructed by the method of uniform random sample. The simulation results fit well with the calibration results. The error between the simulation and the calibration on the parameters of electrostatic factor and energy resolution are 3.2% and 1.5%, respectively. The correlation coefficient between the simulation and the calibration on the relationship of deflection angle and deflection factor is 0.9994. he simulation results show that it can be applied well in the process of plasma instrument design and calibration.
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    Design and Test of an Ultrasonic Flow Meter for Orbital Refueling
    YU Yang, DING Feng-Lin, ZONG Guang-Hua
    2012, 32 (4):  77-83.  doi: 10.3780/j.issn.1000-758X.2012.04.011
    Abstract ( 1668 )   PDF (416KB) ( 1143 )   Save
    An Ultrasonic Flow Meter (UFM) was designed for accurate propellant gauging. Based on the research of transit time measurement, the requirements for pipe structure design were proposed. Computational Fluid Dynamics (CFD) was used to simulate the velocity distribution of four different pipe structures, and an optimal pipe structure was designed based on the CFD result. Chopper stabilized comparator in the signal processing electronics ensured the time measurement accuracy by using the threshold value comparing technique. After calibration, the ultrasonic flow meter can achieve an accuracy of 0.1% for range 0~150g/s. In order to test the function of the flow meter in orbital refueling, a ground simulation experiment was carried out. The result of the ground simulation experiment shows that the implementation of ultrasonic flow meter is practical for orbital refueling and quite necessary for performance observation during the refueling process.
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