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    25 August 2019, Volume 39 Issue 4 Previous Issue    Next Issue
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    Space robot capture collision force control method based on explicit force control
    FANG Qun, CUI Ming-Ming
    2019, 39 (4):  1.  doi: 10.16708/j.cnki.1000-758X.2019.0023
    Abstract ( 93 )   PDF (6328KB) ( 108 )   Save
    Aiming at the collision force control problem of space robots in capturing floating targets, the dynamic model of the space robot′s catching target and the contact collision model with the target are established. The parameters such as the closing speed of the claw and the initial position of the target are analyzed. On the basis of this, the taskfirst inverse kinematics solution method is used to design the capture force control method based on explicit force control, the collision force control method based on external force control and the collision force based on explicit force control. The control method is compared and analyzed. The results show that the collision force control method based on the explicit force control can achieve the collision force control that meets the requirements of stationarity, and the required pedestal thrust and joint control torque are small.
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    Passive positoning algorithm based on single satellite frequency measurement
    HUANG Jing, ZHAO Wei-Wei, CHEN Xue-Hua, LIU Zhe, WANG Gang
    2019, 39 (4):  11.  doi: 10.16708/j.cnki.1000-758X.2019.0024
    Abstract ( 88 )   PDF (2061KB) ( 72 )   Save
    A passive positioning algorithm by single satellite frequency measurement based on the nonlinear optimization theory is proposed. This algorithm utilizes a series of Doppler frequency data acquired by one satellite at different places to locate the radiant points on the earth. Based on this, one Doppler frequency data preprocessing method, and one measurement error separation method based on Polynomial Autoregressive (PAR) model are also provided. Finally, the validity and accuracy of the proposed algorithm is verified by simulation results and engineering data.
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    Simulation and experimental verification of space fuel cell power supply subsystem output performance
    WANG Sen, LEI Wei-Jun, FENG Lei, LIU Jian, WAN Cheng-An
    2019, 39 (4):  18.  doi: 10.16708/j.cnki.1000-758X.2019.0025
    Abstract ( 77 )   PDF (5339KB) ( 80 )   Save
    The relationship between the output characteristics of the proton exchange membrane fuel cell power system and the reactor pressure and temperature is systematically studied. Firstly, the mathematical model of the electric reactor is established and the relationship between the input and the output in Matlab/Simulink is studied. Secondly, the fuel cell discharge regulator(FCDR) is designed for aerospace applications. The simulation starts with connecting the FCDR and electric reactor, and the influence of the input on the output of the FCDR as well as FCDR′s ablity to maintain the bus voltage stable when the loads chang is studied. Finally, the experiments test the electric reactor′s and electric reactor subsystem′s simulations′ validity. The experiments prove the correctness of the simulation, providing a further insight into space fuel cell power systems. The power subsystem provides a firm foundation for the design of the whole power system.
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    Preliminary design and test of attitude control system for lunar CubeSats
    YANG Chi-Hang, LIU Jiang-Kai, LONG Long- , SONG Huan, LI Long, ZHU Ling-Chao, YE Bing-Xu, CHEN Hong-Ru, ZHANG Hao
    2019, 39 (4):  28.  doi: 10.16708/j.cnki.1000-758X.2019.0026
    Abstract ( 128 )   PDF (2728KB) ( 72 )   Save
    CubeSats are miniature functional satellites The increasing interest in CubeSats has uncovered the potential for planetary missions Besides, CubeSats is an excellent educational platform. The preliminary attitude control system is designed and the corresponding hardware is built using commercial products for a lunar mission employing a CubeSat constellation to provide positioning service for landers/rovers on the far side of the moon At the same time, the basic frame and necessary subsystems including the structure, power and onboard computer subsystems, and the attitude experiment platform are constructed Based on the hardware platform, the control model is deeply understood through measuring damping coefficients by experiments A PD control method is designed to control the attitude The numerical and physical simulation results match well, and the CubeSat system achieves accurate attitude maneuver.
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    Satellite attitude control method based on deep reinforcement learning
    WANG Yue-Jiao, MA Zhong, YANG Yi-Dai, WANG Zhu-Ping, TANG Lei
    2019, 39 (4):  36.  doi: 10.16708/j.cnki.1000-758X.2019.0027
    Abstract ( 76 )   PDF (2780KB) ( 90 )   Save
    Aiming at the problem of sudden changes in the attitudes encountered by satellites while performing complex tasks such as discarding a payload or capturing a target, a satellite attitude control method based on the deep reinforcement learning is proposed to restore the satellite to a stable state. Concretely, the attitude dynamics environment of the vehicle is firstly established, and the output of continuous control torque is discretized. Deep Q Network algorithm is then performed to train the autonomous attitude control of the satellite for further processing, and the optimal intelligent output of discrete behavior is rewarded with the stabilization of attitude angular velocity. Finally, the validity of the mechanism is verified by the simulation test. Results analysis illustrates that the deep reinforcement learning algorithm for satellite attitude control can stabilize satellite attitude after the satellite is disturbed by sudden random disturbance, and it can effectively solve the problem of traditional PD controller depending on the mass parameters of the controlled object. The proposed method adopts selflearning to control the satellite attitude, which has strong intelligence and universal applicability, and has a strong application potential for future intelligent control of satellites performing complex space tasks.
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    Research progress of electromagnetic sail propulsion for deep space exploration
    YU Wei-Dong, WEN Xiao-Dong, ZHANG Tian-Ping, LIU Li-Juan
    2019, 39 (4):  43.  doi: 10.16708/j.cnki.1000-758X.2019.0028
    Abstract ( 82 )   PDF (5928KB) ( 87 )   Save
    Electromagnetic sail, a kind of space propulsion technology driven by solar wind, has broad application prospects in deep space exploration missions that require spacecraft working for a long time due to its characteristics of no propellants or less propellants. The basic concepts and main classifications of the electromagnetic sails are introduced. The working principles, system compositions, research status of ESail,PMS and MPS are discussed and followed by the plasma magnetoshell technology. Finally, the research progress of electromagnetic sail propulsion technology is summarized, which provides research direction and development ideas for domestic research in this field.
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    An interferometry method based on signal combination
    LU Wei-Tao, XIE Jian-Feng, CHEN Lue- Ren-Tian-Peng, HAN Song-Tao, WANG Mei
    2019, 39 (4):  54.  doi: 10.16708/j.cnki.1000-758X.2019.0029
    Abstract ( 84 )   PDF (4960KB) ( 64 )   Save
    Aiming at the demand of more accurate interferometry in the following deep space exploration, a novel interferometry scheme based on signal combination is proposed and analyzed. By studying the mainstream signal combination algorithms, an improved Sumple algorithm based on phase comprehension is put forward. This algorithm is more efficient than the original Sumple algorithm, and moreover its combined signal has the same phase performance as that of the reference signal, which is the premise of antenna array technique used for interferometry. Finally, tests are conducted by using phased array data and simulated DOR signal data. The processing results show that the signal combination improves the delay estimation accuracy of interferometry, and is of special meaning in deep space exploration.
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    urface modification  of LiNi0.8Co0.15Al0.05O2 (NCA) cathode material using phosphoric acid
    XU Zhi-Bin, LI Yang, SANG Lin, DING Fei
    2019, 39 (4):  62.  doi: 10.16708/j.cnki.1000-758X.2019.0030
    Abstract ( 82 )   PDF (3778KB) ( 95 )   Save
    he next generation of space products put forward higher demand for energy storage system, and the surface modification method is proposed to improve the cyclic stability of LiNi0.8Co0.15Al0.05O2 (NCA) cathode material in lithium ion batteries. By using phosphoric acid (H3PO4) to treat the NCA cathode materials, H3PO4 reacts with the lithiumcontaining alkaline substances on the surface of NCA, so as to generate a stable and conductive Li3PO4 interface layer on the surface of NCA particles. As a result, the H3PO4modified NCA shows better capacity retention (170.5mA·h/g,94%) and lower impedance after 50 cycles than the bare one, which is attributed to the presence of the Li3PO4based coating layer. H3PO4 surface modification method has positive effects on the electrochemical performance and structural integrity of the NCA electrode materials.
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    Study on the inhibition effect of modified Allan variance on Flicker PM noise
    LIU Ying-Qian, CHEN Qiang, XUE Ren-Kui, LAN Xue-Mei, ZHANG Zhen-Zhi
    2019, 39 (4):  68.  doi: 10.16708/j.cnki.1000-758X.2019.0031
    Abstract ( 115 )   PDF (1184KB) ( 85 )   Save
    In the time and frequency field, Allan variance is utilized in general to indicate frequency stability. Allan variance can not inhibit Flicker PM effectively because it′s defective algorithm. In order to reduce the impact of noise on frequency stability, frequency stability should be indicated by modified Allan variance. Modified Allan variance for inhibition mechanism of Flicker PM is analyzed. Through the satellite commonview method, the comparative data of hydrogen clock and UTC(NIM) are evaluated. Then, the noise model is used to demonstrate the results of evaluation. The effectiveness of the modified Allen variance against Flicker PM inhibition is verified.
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    Development and ignition characteristics of miniature gallium field emission electric propulsion thruster
    XU Ming-Ming, KANG Xiao-Ming, GUO Deng-Shuai, LIU Xin-Yu, HE Wei-Guo
    2019, 39 (4):  73.  doi: 10.16708/j.cnki.1000-758X.2019.0032
    Abstract ( 65 )   PDF (3944KB) ( 68 )   Save
    In order to meet the demand for propulsion systems of micronano spacecraft such as the cubic satellite, the first needletype miniature gallium field emission electric propulsion thruster in China was developed. The problem that gallium is difficult to fully wet the tungsten needle under vacuum environment was solved by increasing the wetting temperature. The thruster′s stable ignition was realized, and the thruster′s ignition characteristics under different wetting temperatures and different geometric parameters were tested. The relationship is obtained that the emission current increases as the wetting temperature increases, the pole spacing decreases, and the inner hole diameter of absorbing pole increases. The theoretical thrust under different emission currents is given by formula calculation.The electric field strength under different geometric parameters is obtained by simulation, and the reason why the geometric parameters affect the emission current is revealed.
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    Design and high velocity impact test verification of flexible space debris protection shield
    WANG Wei, ZHENG Shi-Gui, CHANG Jie
    2019, 39 (4):  82.  doi: 10.16708/j.cnki.1000-758X.2019.0033
    Abstract ( 74 )   PDF (2071KB) ( 66 )   Save
    Inflatable and deployable space module is the most desired for future space stations and space structures. The outer shell of such inflatable module is made up of several layers for debris protection, seal and thermal control. In order to protect the module from the debris and make it easy to be packaged and deployed, the outer protection shields of such modules were designed to be made of polyurethane foam and some kinds of fabrics. This paper proposes a design of such flexible and inflatable protection shield based on the multishock structure. The parameters of such shields are determined by homemade Basalt fiber and aromatic polyamide fiber. Before test verification, the design parameters of such debris shield are determined by simulation based on multishock structure and such ballistic limit equation. And then High Velocity Impact (HVI) test program was conducted to verify that the design parameters can meet the design requirement of the inflatable and deployable structure.
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