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    25 October 2021, Volume 41 Issue 5 Previous Issue   
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    Survey of space observations and research on topography and geomorphology of Deimos
    LI Tieying, GU Zheng, ZHOU Xiaoling
    2021, 41 (5):  1-9.  doi: 10.16708/j.cnki.1000-758X.2021.0061
    Abstract ( 109 )   PDF (4775KB) ( 198 )   Save
    Deimos is one of the two natural satellites of Mars, and researchers used Mars probes to observe Deimos and did research on topography and geomorphology of Deimos. In this paper, the basic information and the origin hypotheses of Deimos are described, and then a detailed description for each observation activity is made one by one, finally the research results about Deimos are analyzed. The conclusions show that there are craters, regolith, bright albedo markings and blocks on Deimos surface and the surface matter has downslope movement. According to the situation that there is not enough exploration about Deimos, some advices for future exploration are given.
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    Newton electric propulsion system for space gravitational wave detection
    LIU Hui, WANG Shangsheng, YU Daren, ZHAO Mingxuan, ZHENG Siyuan, CHEN Ye
    2021, 41 (5):  10-20.  doi: 10.16708/j.cnki.1000-758X.2021.0062
    Abstract ( 82 )   PDF (5181KB) ( 78 )   Save
    To meet the special requirements for drag-free control technology in space gravitational wave detection task, main alternative propulsion types are introduced, such as cold gas thruster, ion thruster, multistage cusped magnetic field Hall thruster and colloid thruster. Life assessment of electric propulsion system for space gravitational wave detection task is analyzed, and current research status of life tests for electric propulsion system at micro-Newton level is reported. Examples are given to illustrate the main life prediction methods of electric propulsion devices, including semi-empirical model prediction, numerical simulation prediction, data-driven prediction and reliability evaluation methods at system level. With the summary of the research status on life assessment of the micro-Newton electric propulsion system, development ideas are proposed.
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    Effect of shielding materials on satellite internal dielectric charging effects in Jupiter orbits
    YU Xiangqian, SHI Weihong, SONG Siyu, CHEN Hongfei, ZONG Qiugang, ZOU Hong, CHEN Ao, WANG Yongfu
    2021, 41 (5):  21-27.  doi: 10.16708/j.cnki.1000-758X.2021.0063
    Abstract ( 71 )   PDF (2991KB) ( 61 )   Save
    In the space environment around Jupiter, the dominant particles are high-energy electrons with E > 1 MeV (and can be higher than 100MeV), which can cause internal dielectric charging effects in spacecraft electronics. Huge mass is required to shield these electrons to reduce the incident internal flux to a safe level. The GEANT4 and RIC (radiationinduced conductivity) Monte Carlo toolkit method was used to study an optimum single shielding material design for high energy electrons during a Jupiter mission. Al, Ti, Fe, Cu, Ta and Pb were investigated as possible materials for spacecraft shielding. Calculation results indicate that, to mitigate internal dielectric charging effects during a Jupiter mission, lowZ materials provide less-efficient shielding with the same areal mass than high-Z materials. Therefore, shielding mass can be saved by using Ti, Fe, Cu, Ta or Pb, instead of Al which is commonly used in Earth orbits.
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    Influence of the surface error of pentaprism on the steering angle of central incident ray
    WEN Zhongkai, XU Mingming, ZHANG Qingjun, LI Shuang
    2021, 41 (5):  28-36.  doi: 10.16708/j.cnki.1000-758X.2021.0064
    Abstract ( 51 )   PDF (2683KB) ( 20 )   Save
    In order to solve the problem that the surface error of pentaprism will cause the steering angle error of the emergent ray, which affects the accuracy of the multi-optical axis calibration of space photoelectric tracking and aiming system, a new method was proposed to study the effect of the surface error of the pentaprism on the steering angle of the emergent ray. Firstly, the best fit spherical vector height was used to appropriately simplify the working surface model of pentaprism under the premise that the irregularity of the pentaprism is small. The steering angle formula of the emergent ray was derived, and the influence factors of the steering angle error of the emergent ray were limited to the joint action of six correlative random variables. Then, a dimensionality reduction analysis method by combining the typical application scenarios of pentaprism was proposed, which removes the correlation among the six variables, and the steering angle error calculation formula after dimensionality reduction was derived. The calculation results of the formula show that the maximum relative errors of the steering angle error in the direction of the principal section and the direction perpendicular to the principal section are only 2.14% and 0.31%, which meets the requirements of accuracy analysis. Finally, the technical test of the pentaprism was carried out through experiments, and the results show that the deviations of the steering angle errors in the direction of the principal section and the direction perpendicular to the principal section between the average values of the experimental test and the calculated results of the dimensionality reduction formula a ±0.25″ and ±0.15″, which is acceptable. Therefore, the simplified model and the dimensionality reduction analysis method proposed are both feasible, and provide a new research idea and analysis method for the related research of surface error of pentaprism.
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    Kinematic modeling and analysis of support mechanism for modular deployable antenna
    FAN Xiaodong, ZHENG Xijian, TIAN Dake, GAO Xu, LIU Zhaojing, ZHANG Ke, MA Xiaoou
    2021, 41 (5):  37-49.  doi: 10.16708/j.cnki.1000-758X.2021.0065
    Abstract ( 74 )   PDF (7373KB) ( 109 )   Save
    The characteristics of strong expansibility, high flexibility and good adaptability are provided by a modular deployable antenna. The largeaperture development trend of the deployable antenna can be met by such an ideal structural form in the future. To study the multi-module linkage deployment movement characteristics of the deployable antenna support mechanism composed of hexagonal prism modules, a kinematic modeling method of multi-module linkage deployment was proposed. According to the structure composition and deployment principle of the deployable antenna, the spatial geometric model of key points of the deployable antenna mechanism was established. Based on the D-H method and coordinate transformation theory in robotics, kinematics models of a basic unit, single module and multi module were established respectively. Finally, the kinematics model was verified and analyzed by MATLAB numerical simulation software. The results show that the kinematics model can be used to analyze the multi-layer deployable antenna mechanism, coordinated linkage and synchronous deployment can be realized by each module. At the same time, a research basis is provided by the model for the dynamic characteristics analysis, power source configuration and optimization of the mechanism.
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    Dynamic simulation of the deployment process of super large loop antenna belt
    HU Jianfeng, YANG Jungang, XIAO Yong, WAN Xiaoping, FENG Tao, WANG Yong, ZHENG Bing
    2021, 41 (5):  50-56.  doi: 10.16708/j.cnki.1000-758X.2021.0066
    Abstract ( 66 )   PDF (3548KB) ( 27 )   Save
    The middle flexible belt is an important part of the loop deployable antenna. With the explosion of retracting actuator, the composite belt and the loop truss are expanded synchronously. Due to the strong flexibility of the composite belt, it will rebound around the fixed end of the root. Therefore, there is a risk of collision between the metal joint and the composite thinwalled pipe on the truss during the deployment process. As the antenna diameter increases, the risk will continue to increase. Based on the flexible multibody dynamics theory, the dynamic modeling and simulation of the belt deployment process of the super large loop antenna were carried out. On this basis, the minimum distance between the metal joint and the loop truss during deployment process was mainly related to belt damping rate and the truss preview speed. After further research, it was found that the bigger the damping rate of the composite belt, the longer the minimum distance between the metal joint and the loop truss during deployment, and that the faster the truss preview speed, the shorter the minimum distance between the metal joint and the loop truss during deployment. In addition, the law of change of the minimum distance between the metal joint and the loop truss in the process of deployment under the condition of failure of ratchet device in space was obtained. This research can provide a basis for the optimal design of the super loop antenna structure and the prediction of the belt deployment in space.
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    Study on dynamics of satellite hold-down and release mechanism with nonlinear characteristics
    LIU Hanwu, ZHANG Hua, FANG Xianliang
    2021, 41 (5):  57-64.  doi: 10.16708/j.cnki.1000-758X.2021.0067
    Abstract ( 46 )   PDF (3739KB) ( 28 )   Save
    In view of the local non-linear characteristics of the new hold-down and release mechanism for satellites, a local non-linear structure model was proposed. The forcedisplacement curves of the local non-linear structure were obtained by simulating the loading. Based on the actual working conditions of the structure, the selection principle of equivalent stiffness load and displacement limit of the structure was defined, and the equivalent stiffness value interval of the structure was solved. Finally, an interval uncertainty analysis was carried out for the dynamic characteristics of the antenna. The results of the analysis are in good agreement with the test results. The basic frequency error of the antenna is less than 10%, meeting the requirements of engineering application. The validity of the analysis method was illustrated. The interval analysis method of equivalent stiffness of local nonlinear structure proposed in this paper provides a solution for the nonlinear dynamic analysis of new hold-down and release mechanism of satellite antenna, and also provides a reference for other local nonlinear structural dynamic analysis.
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    Experimental research on discharge characteristics of LHT40 low power Hall thruster
    CHEN Xinwei, GU Zuo, GAO Jun, GUO Ning, WANG Shangmin, ZHAO Yong, FENG Jie, SHI Kai, PU Yangxu, LI He
    2021, 41 (5):  65-74.  doi: 10.16708/j.cnki.1000-758X.2021.0068
    Abstract ( 46 )   PDF (6187KB) ( 31 )   Save
    In order to obtain the discharge characteristics of the 300W class hybrid-excited low-power Hall thruster, a high-precision micro-thrust laser measurement device and an integrated ion current density diagnostic device were used to access the characteristics of thrust, specific impulse, efficiency, beam divergence angle and mass utilization efficiency of the thruster for different operating conditions. There is a maximum for thrust, specific impulse and anode efficiency under discharge voltages from 200V to 300V. The discharge current and voltage exhibit damping-free harmonic oscillation, and the first-order frequency is about 4.05kHz. Under constant electric field and magnetic field, the beam ion current density presents a bipolar diffusion characteristics. When the anode flow rate is increased to 0.95 mg/s, the ion current density shows a typical doublepeak structure, and the mass utilization efficiency is positively correlated with anode mass flow rate.
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    Structural design and optimization of the joint-assisted exoskeleton in active spacesuit
    LI Zhaoyang, DAI Yuehong, HU Jiejun, WANG Junyao
    2021, 41 (5):  75-84.  doi: 10.16708/j.cnki.1000-758X.2021.0069
    Abstract ( 55 )   PDF (8258KB) ( 43 )   Save
    A joint-assisted exoskeleton scheme was designed for spacesuits to get rid of the influence of spacesuits’ resistance moment on astronauts' future space operation, planetary exploration and skeletal muscle recovery training. Firstly, the first-generation prototype of the joint-assisted exoskeleton was developed based on the structural analysis of the simulated spacesuit. Then, according to the feedback, the structure of the first-generation exoskeleton prototype was optimized. The design model of the second-generation exoskeleton prototype was preliminarily determined, and finite element software was used to carry out the static analysis and modal analysis of the exoskeleton prototype under load condition. Finally, the structural dimensions of the second-generation exoskeleton prototype was further optimized, the overall mass decreased by 19.34% and 40.03% compared with the unoptimized second-generation and the first-generation prototypes, which verified the feasibility and validity of the exoskeleton prototype structural optimization scheme. The simulation results provide a theoretical basis for the structural dynamics analysis and control system development of the active spacesuit.
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    Resource allocation in high throughput multibeam communication satellite systems
    WANG Lei, ZHENG Jun, HE Chuan, YAN Xuefei
    2021, 41 (5):  85-94.  doi: 10.16708/j.cnki.1000-758X.2021.0070
    Abstract ( 56 )   PDF (3765KB) ( 28 )   Save
    Resource allocation plays an important role in the performance of new generation of high throughput multibeam communication satellite(HTMCS) systems. The static and single dimension methods for resource allocation were normally proposed for previous communication satellite systems with non-flexible payloads and uniform distribution of users’ capacity demands, which has seriously constrained the performance of the HTMCS systems. A joint power and bandwidth resource allocation model for the HTMCS systems was built, with the consideration for beam interference, flexible payloads and nonuniform distribution of capacity demands. Meanwhile, a genetic algorithm with high efficient search control strategies was implemented to solve this model. Finally, several types of dataset were employed with different capacity demands and distribution profile between beams to verify the proposed method. Experimental results show that the method can reduce the unmet capacity demand(UCD) by 71.09%, 40.47% and 16.31% compared to the current static method for the total capacity demand of 90Gbit/s, 110Gbit/s and 130Gbit/s respectively.
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    Fast and precise scanning and tracking control of space beam based on adaptive LMS algorithm
    XIONG Zijun, LIU Lei, YANG Hongjie
    2021, 41 (5):  95-102.  doi: 10.16708/j.cnki.1000-758X.2021.0071
    Abstract ( 40 )   PDF (6961KB) ( 12 )   PDF(mobile) (6961KB) ( 22 )   Save
    Fast and precise beam scanning control is strictly required in aerospace, especially the space precise optics. To meet the requirements of fast and precise beam control for space science and technology as well as national defense applications, the adaptive least-mean square (LMS) algorithm was given to control the beam pointing and tracking of piezoelectric steering mirrors. Firstly, the adaptive LMS control method and the model identification of fast steering mirror were described. Then, the piezoelectric fast steering mirror model was identified and compared with the known reference model. The tracking control performance of the adaptive LMS algorithm under different frequencies and iterative steps was simulated. Finally, the unknown piezoelectric steering mirror was identified by experiments, and the adaptive LMS algorithm was designed for the input-output scanning and tracking control. The experimental results show that the tracking errors of the adaptive LMS algorithm are 2.5%(3σ), 1.9%(3σ) and 2.4%(3σ) for 2Hz, 10Hz and their compound sinusoidal scanning signals, respectively, which are better than the PI control errors. The adaptive LMS algorithm can effectively track multi-frequency reference signals and provide a reliable technical means for fast and precise space beam pointing and tracking.
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    UKF filtering algorithm for SINS/CNS/GNSS integrated navigation in launch inertial coordinate system
    QIAO Yuxin, LIN Xueyuan, ZHANG Jisong, CHEN Xiangguang
    2021, 41 (5):  103-109.  doi: 10.16708/j.cnki.1000-758X.2021.0072
    Abstract ( 42 )   PDF (3255KB) ( 42 )   Save
    The integrated navigation system model of missile system is often established under the launch inertial coordinate system, and the strapdown inertia/celestial navigation/satellite navigation (SINS/CNS/GNSS) is one of the most studied integrated modes. The state equation of the integrated navigation system is strongly nonlinear, and the common filtering method is extended Kalman filtering (EKF). In order to improve the precision and reliability of integrated navigation system, the UKF filter model of the integrated navigation system was designed, directly using the attitude, position and velocity parameters as part of the state, and the attitude and position provided by CNS and GNSS to form the measurement equation.The generation process of attitude sample points, mean value and variance was given. Simulation results show that, compared with EKF algorithm, UKF algorithm can improve the accuracy of navigation parameters by about 20%~30%, and that the realtime performance of the system can be guaranteed.
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    Direct sampling method for weak signal of magnetically selected cesium atomic clock
    GAO Tianxiang, WANG Ji, ZHAO Yulong, DONG Pengling, HUANG Liangyu, LIU Zhidong
    2021, 41 (5):  110-115.  doi: 10.16708/j.cnki.1000-758X.2021.0073
    Abstract ( 37 )   PDF (3665KB) ( 19 )   Save
    The output frequency of the magnetically selected cesium atomic clock is related to the weak current signal output by the cesium beam tube, which affects its frequency stability. In order to improve its frequency stability, on the basis of the comparison between the weak signal voltagefrequency conversion and A/D(analog-to-digital) direct sampling of the main servo circuit of the magnetically selected cesium atomic clock, an A/D direct sampling circuit was designed based on the DSP28335 chip, using CAN bus communication technology to communicate with main control CPU board, and the wholeclock closed-loop locking scheme was realied. The experiment was compared with the existing voltagefrequency conversion method of the measured magnetically selected cesium atomic clock. The result shows that, compared with the voltagefrequency conversion method, the designed A/D direct sampling method reduces the relative frequency deviation range of the magnetically selected cesium atomic clock and improves the short-term frequency stability, presenting certain practical value.
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    High-accuracy target tracking estimation based on dual Kalman filter
    QIN Jiankai, LI Peng
    2021, 41 (5):  116-124.  doi: 10.16708/j.cnki.1000-758X.2021.0074
    Abstract ( 41 )   PDF (4127KB) ( 26 )   Save
    For cooperative spacecraft driven by continuous force, the dual unscented Kalman filter (DUKF) was used to estimate the state and acceleration. The state filter and parameter filter can cooperate mutually to ensure higher filter accuracy of estimation for motions and parameters, so that the motion tracking of cooperative targets can be realized. Compared with cooperative targets, non-cooperative targets perform maneuvering with unknown forces and occurrence time, so this brings more challenges for information acquisition and state estimation. For non-cooperative spacecraft, we formulated the relative motion equation, and utilized the observation information from space-based platform for state estimation. Two extended Kalman filters (EKFs) and semilatus rectum were used for maneuvering detection to estimate the motion state of maneuverings with multiple unknown pulses. The simulation results show that DUKF has faster rate of convergence and better performance of tracking error for state and acceleration estimation of cooperative spacecraft. For non-cooperative spacecraft, the effectiveness of the maneuvering detection strategy combining with the filter switching strategy is verified through comparison. The proposed method detected multiple maneuvers and reduced misjudgments
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    Remote sensing image registration method based on embedded FPGA accelerated ORB algorithm
    ZHAO ZhiYi, SUN Ting, LI Feng, XIN Lei, LU XiaoTian, LIANG Liang
    2021, 41 (5):  125-135.  doi: 10.16708/j.cnki.1000-758X.2021.0075
    Abstract ( 79 )   PDF (9548KB) ( 206 )   Save
    With the limited computing units on satellites, it generally takes a long time for the on-board embedded processor to process the remote sensing image alignment. The programmable logic gate arrays (FPGAs) can be utilized to accelerate image processing using their internal programmable components. In this paper, we proposed a remote sensing image registration method based on Xilinx's ZYNQ chip accelerated ORB algorithm. It was employed to align the remote sensing images with 3000×3000 pixels, which shortened the time consumption and improved the computational energy efficiency of ORB algorithm. The parallel computing architecture of ORB algorithm with multi-branch single-layer pipeline was realized by using FPGA that can realize a real parallel computing circuit. A combination of hardware and software was used to implement the architecture, which can handle images with different resolutions and can be configured with the number of feature points flexibly. The results show that the accelerated ORB alignment method can provide higher accuracy. Compared with software method, the offset precision loss is less than 0.05 pixel for the OVS-1A remote sensing images and is less than 0.9 pixel for the GF-4 remote sensing images. The time consumption of the ORB algorithm implemented on ZYNQ7020 is reduced by 5750%.
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