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    25 February 2021, Volume 41 Issue 1 Previous Issue   
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    Research status and prospect of chemical-electrospray dual-mode propulsion system
    WU Qinqin, LIU Xinyu, DENG Hanwen, KANG Xiaoming
    2021, 41 (1):  1-12. 
    Abstract ( 201 )   PDF (2873KB) ( 208 )   Save
    The traditional chemical propulsion and electric propulsion have different characteristics and application ranges. The chemical propulsion has a thrust range from ~mN to ~N. In comparison with the electric propulsion, it has the characteristics of high thrust and wide thrust range. The electric propulsion can obtain a maximum specific impulse of thousands of seconds and a minimum thrust of ~μN. However, there are limitations for those two modes, and some complex space missions are difficult to be completed independently by any of them. The dual-mode propulsion system includes both chemical mode and electric mode, and has the characteristics of high specific impulse and wide thrust range, which can improve the flexibility of the spacecraft mission. Monopropellant chemical propulsion paired with ionic liquid electrospray propulsion has received the most attention recently. The principle and characteristics of the monopropellant-electrospray dual-mode propulsion system are introduced. The research status of dual-mode propulsion is summarized, and the existing problems and challenges are analyzed.
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    An autonomous orbit determination algorithm of XPNAV-1 based on extended Kalman filtering
    DING Taowei, SHUAI Ping, HUANG Liangwei, ZHANG Xinyuan
    2021, 41 (1):  13-21.  doi: 10.16708/j.cnki.1000-758X.2021.0002
    Abstract ( 180 )   PDF (2056KB) ( 119 )   Save
    The world′s first dedicated pulsar navigation test satellite, X-ray pulsar-based navigation-1(XPNAV-1), was successfully launched by China in November, 2016. The satellite is operating normally in orbit, and a large amount of observation data has been acquired. The measured data of a single pulsar was used to verify the effectiveness of the satellite orbit improvement and the pulsar navigation system through the geometric constraint method. However, the longterm orbit determination process using a single pulsar had divergence problems. Based on the XPNAV-1 satellite expansion test mission and the need for subsequent development of pulsar navigation, the observation data of multiple pulsars was used to study the autonomous orbit determination algorithm of satellites based on extended Kalman filter (EKF). Firstly, the orbital mechanics model and observation equations of the satellite were established; secondly, the EKF filter algorithm and the observability analysis method of the piecewise constant system (PWCS) were discussed; finally, through a comprehensive analysis of the XPNAV-1 satellite observation data, pulsar coverage of satellite orbits and observability of system status, the autonomous orbit determination algorithm experiment was carried out. The test results show that the filtering process of the autonomous orbit determination algorithm based on EKF converges, which verifies the rationality and effectiveness of the algorithm.
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    Dimensional stability analysis of the satellite structure based on in-orbit temperature measurement data
    LUO Wenbo, ZHANG Xinwei, QIAN Zhiying, ZHANG Ling, BAI Gang, MO Fan, LU Qingrong, YIN Yazhou, FU Weichun
    2021, 41 (1):  22-28.  doi: 10.16708/j.cnki.1000-758X.2021.0003
    Abstract ( 145 )   PDF (4096KB) ( 85 )   Save
    Aiming at the critical problem of dimensional stability of high precision mapping satellite structure, an inversion algorithm of in-orbit temperature field of satellite structure was proposed by using the analysis model and the variation rule of in-orbit temperature. Furthermore, the predictive methods of the short-term and long-term angle stability of payloads mounting interface were proposed. And then based on the above methods, the predictive values of short-term and long-term structure stability of GF-7 satellite within the first month were presented. Finally, the results of short-term stability were analyzed statistically. The results show that the prediction results of the short-term stability meet the requirements.
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    Research on real-time precise point positioning with iGMAS ultra-fast ephemeris#br#
    XU Weizheng, KANG Guohua, PENG Pan, ZHOU Hongtao, LIU Zongqiang, ZHAO Teng
    2021, 41 (1):  29-37.  doi: 10.16708/j.cnki.1000-758X.2021.0004
    Abstract ( 135 )   PDF (8161KB) ( 40 )   Save
    The China-led International GNSS Monitoring & Assessment System (iGMAS) differs from the IGS system (international GNSS service, IGS) in product accuracy. Real-time precise point positioning(PPP) applications are mostly based on IGS real-time and near real-time products. To improve this situation, we aimed at iGMAS product characteristics and the demand for ultra-fast products with real-time PPP, evaluated the accuracy and stability of iGMAS ultrafast ephemeris, designed an iGMAS product real-time/post-event download application, and carried out real-time precise point positioning research based on iGMAS ultra-fast ephemeris through combining with NovAtel OEM617 dual-frequency receiver. The experimental results show that the positioning error can converge to the decimeter level after 23 minutes, which is an order of magnitude higher than the original positioning accuracy of the receiver and has good stability. The root mean square error of the positioning error in the E/N/U direction is 7.2cm, 6.4cm, 15.2cm, similar to IGS ultra-fast ephemeris in real-time PPP experiment. This study implements a complete solution for iGMAS data acquisition, evaluation, and real-time PPP applications, verifies performance of iGMAS ultra-fast products and provides reference for the application of iGMAS products.
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    An improved adaptive genetic algorithm for multi-satellite area observation scheduling
    FAN Yu, LIU Yingying, ZHOU Jun
    2021, 41 (1):  38-47.  doi: 10.16708/j.cnki.1000-758X.2021.0005
    Abstract ( 162 )   PDF (2370KB) ( 139 )   Save
    Aiming at the shortcomings of the traditional optimization algorithm in solving the multi-satellite regional scheduling problem such as slow convergence speed and being prone to fall into the local optimal solution, an improved adaptive genetic algorithm was proposed. The algorithm uses Monte Carlo method combined with Hamming distance to give a better initial population. According to the average Hamming distance of the population, the execution sequence of crossover and mutation operations are determined. The Sigmoid function and Gaussian function are combined to design the adaptive nonlinear crossover rate and mutation rate based on the individual fitness of the population. The dual elite retention strategy and tournament strategy are combined to ensure the inheritance of the optimal individual. Dual shutdown condition is used to improve the search efficiency of the algorithm. Finally, experiment shows that the method can significantly improve the global search ability, accelerate the convergence speed of the algorithm, and effectively improve the observation efficiency of satellites.
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    Error analysis and prediction of Klobuchar ionospheric model 
    PENG Yaqi, LI Chonghui, WANG Yiwen, WEI Wulei, DING Baichao, LIU Yangqian
    2021, 41 (1):  48-54.  doi: 10.16708/j.cnki.1000-758X.2021.0006
    Abstract ( 263 )   PDF (5519KB) ( 115 )   Save
     Ionospheric delay error is one of the most important error sources in global navigation satellite system (GNSS). At present, the most widely used ionospheric delay correction model is the Klobuchar parameter model, but the correction rate of this model can only reach about 60%, which cannot meet the increasing accuracy requirements. The high-precision ionospheric grid data published by the international GNSS monitoring & assessment system (iGMAS) were used as a reference value to calculate and analyze the error of Klobuchar ionospheric model. The results show that the error in the mid latitude region has obvious periodic characteristics. To further improve the correction accuracy of the Klobuchar ionosphere model in the mid-latitude region, a Klobuchar ionospheric error prediction model was established based on particle swarm optimization back propagation (BP) neural network. Error prediction was made by taking the sample data of October 2019 as an example. The results show that accuracy can be improved to about 90% by using the model to compensate for the ionospheric delay error in the mid latitude region.
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    Dynamic modeling for the deployment of the folded truss of space diffraction telescope
    HUANG Zebing, LIU Jinyang, YUAN Tingting, HOU Peng
    2021, 41 (1):  55-63.  doi: 10.16708/j.cnki.1000-758X.2021.0007
    Abstract ( 144 )   PDF (4360KB) ( 111 )   Save
    In the process of truss deployment of space diffraction telescope, the moment of unfolding and locking of each truss element will cause the elastic vibration of the member and have a great impact on the star and the main mirror. On the basis of considering the elastic deformation of the truss components, a flexible multibody system dynamics model with variable topology was established for the truss expansion and locking process according to the changes of the system topology and constraints, and the dynamic numerical analysis was carried out. When the truss element was locked, the action of the locking mechanism was simulated by applying strengthening torque and damping at the joint. The numerical simulation results show that at the moment of locking, the truss vibrates greatly in the longitudinal direction, and the impact force on the star and the main mirror shows a peak value, and each peak value is different and changes periodically. This phenomenon is caused by the elastic deformation of the flexible parts of the truss. The research results provide a technical reference for the structural design and dynamic control of the space diffraction telescope.
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    Multi-objective robust attitude control via DPSO algorithm for flexible spacecraft 
    WANG Mengfei, ZHANG Jun
    2021, 41 (1):  64-74.  doi: 10.16708/j.cnki.1000-758X.2021.0008
    Abstract ( 152 )   PDF (4307KB) ( 98 )   Save
    Attitude control system with high performance for complex spacecraft is the foundation of modern space mission, and multiple objectives such as robustness, convergence speed, accuracy and control energy are required. However, most of the current control systems are designed for a single objective. Aiming at the problem of multi-objective attitude control for large flexible spacecraft, a robust design method based on differential particle swarm optimization algorithm and output feedback was proposed. Firstly, the dynamic model with parameter uncertainty was derived. Then, the differential particle swarm optimization algorithm and the linear matrix inequality (LMI) expression of robust D-stability were given. Finally, under the regional pole constraint and Pareto optimal principle, the proposed algorithm was used to optimize the objectives about disturbance suppression and control energy. The feedback gain matrix was obtained. This method satisfies the requirement of multiobjective constraints and has certain effect on vibration suppression. In the multi-objective problem with regional pole assignment, it avoids the conservatism of the traditional LMI method, and also solves the difficulty of selecting the weighting coefficient when transforming multiple objectives into one index function. A simulation example illustrates the effectiveness of the proposed method. Compared with the traditional PID control, the steady-state error of attitude can be reduced by about 54% under disturbance.
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    An attitude hybrid control method for earth-orienting satellite systems with 2-SGCMGs and magnet torquers
    LEI Yongjun, Yuan Li, LIU Qirui, LIU Jie
    2021, 41 (1):  75-83.  doi: 10.16708/j.cnki.1000-758X.2021.0009
    Abstract ( 144 )   PDF (3319KB) ( 79 )   Save
    The attitude control problems were investigated for the earth-oriented three-axis stabilized satellite with a SGCMGs system that only two control moment gyros can be utilized for the others’ failures, and a hybrid control method combining 2 SGCMGs with magnet torquers was proposed to overcome the robustness deficiency of the 2-SGCMGs underactuated system. The nominal gimbal angles for the zero-momentum system were derived with the geometric method. On the basis of the nominal SGCMG gimbal configuration, a novel control frame was established to divide the 3dofs torque command space into two orthogonal subspaces, in which the control commands can be implemented with 2 SGCMGs and magnet torquers individually, and the decoupled control was in turn accomplished for the two different type actuators with significance of difference. Moreover, implementation algorithms of CMG gimbal rate commands and magnet torquer dipole moment commands were also presented. Finally, the effectiveness and robustness of the proposed method were demonstrated by the numerical simulation for the satellite dynamics in the presence of space environmental disturbance torques, and high accuracy performances were achieved with the attitude error less than 0.05° and the attitude stability higher than 0.0005°/s, which can satisfy the general application requirements of high resolution earth remote-sensing satellites.
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    Research on capture and recovery of low-orbit useless targets
    WANG Liwu, LIU Anmin, XU Wangjing , ZHANG Qingbin, WANG Guangxing, LU Yuanyuan
    2021, 41 (1):  84-90.  doi: 10.16708/j.cnki.1000-758X.2021.0010
    Abstract ( 152 )   PDF (4722KB) ( 88 )   Save

    The increasing space debris has a great influence on space activity. It has already been an actual problem how to deal with the threat of space debris to spacecraft. Aiming at the problem of low-orbit large-scale useless target recovery, a new combined flexible capture and recovery scheme was proposed based on the concept of space-based recovery technology. A space net was projected to capture the abandoned target which was passively de-orbited through the inflatable dragincreasing method. Then IRDT was utilized in reentry, deceleration and return to the ground. A dynamic model was established, and simulation calculation analysis was carried out. The simulation results show that the scheme is technically feasible and can be used for the capture and recovery of future space targets.

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    Optimization of in-orbit backup scheme for medium orbit Walker navigation constellation
    WANG Xuyu, HU Min, ZHAO Yulong, ZHANG Xueyang, LI Jiuyang
    2021, 41 (1):  91-99.  doi: 10.16708/j.cnki.1000-758X.2021.0011
    Abstract ( 142 )   PDF (5113KB) ( 56 )   Save
    Aiming at the optimization problem of in-orbit backup scheme of medium orbit Walker navigation constellation, the optimization design method of in-orbit backup satellite orbital position was proposed firstly. Considering that backup satellites and working satellites provide services jointly during the constellation operation, orbital position optimization model was established with selecting PDOP value and number of visible satellites as optimization indexes, and based on the NSGA-II algorithm, the simulation analysis was carried out on the improvement of the service performance of the navigation constellation by backup satellites under different orbital positions. Then, based on the optimization results of backup satellites orbital position, the orbit maneuver model of replacement of in-orbit backup satellite was established, and the backup satellites replacement scheme with the minimum replacement time as the optimization objective was determined by considering the velocity increment and replacement time. The results show that in-orbit backup scheme proposed in this paper can effectively meet the design requirements of backup satellites, enhance the service performance of the navigation constellation, realize the rapid replacement of the failed satellite, and provide reference for the construction of the backup satellite of the navigation constellation. 
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    Analysis and experiment on multicarrier passive intermodulation in high power component
    WEI Huan, WANG Xinbo, BAI He, CUI Wanzhao
    2021, 41 (1):  100-105.  doi: 10.16708/j.cnki.1000-758X.2021.0012
    Abstract ( 112 )   PDF (2206KB) ( 71 )   Save
    Passive intermodulation (PIM) is an inevitable problem in communication systems and is becoming much more serious with characteristics of higher power, wider bandwidth and higher receiving sensitivity of satellite payload. The common method of double carriers for analyzing PIM has been unfit for modern communication systems with complex payload. The proposed analysis and algorithm for multicarrier is an effective way to solve multicarrier passive intermodulation interference, using nonlinear modal of PIM to forecast power level. Analysis and calculation on TNC-KK connector show that three intermodulation frequencies were generated in the receiving frequency band. Comparing the intermodulation power level calculated by the nonlinear model with that measured by the multicarrier experiment, the max error among the three intermodulation frequencies was less than 5dB. The analysis method is beneficial for multicarrier passive intermodulation of high power microwave components and can provide reference for the measurement of multicarrier passive intermodulation.
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    Research on data interaction technology of navigation constellation satellite-satellite-earth integrated network
    WANG Qi, GU Yanan, WANG Bo
    2021, 41 (1):  106-112.  doi: 10.16708/j.cnki.1000-758X.2021.0013
    Abstract ( 131 )   PDF (3030KB) ( 74 )   Save
    The data interaction mechanisms between the inter-satellite link based on timedivision polling chain-built mode and the fixed satellite-earth link are incompatible, which is not conducive to the efficient joint data interaction of navigation constellation and ground. It was proposed to extend the inter-satellite link to the ground by the satellite-earth link of the same signal system to realize the unification of satellite-satellite-earth data transmission and processing mechanism and the integration of network resources control with a small amount of ground station resources and unified network planning, enabling the satellite-satellite-earth data of efficient and accurate interaction. Firstly, the design and deployment method of the ground station and the integrated resource scheduling scheme were defined. Secondly, it was pointed out that the core of the integrated network topology planning is the distribution of the satellite chain, and the optimal ranking method and the ranking priority strategy of the domestic satellite chain were given. Represented by the shortest path routing, a route planning method was defined to search the transmission path according to time forward. Lastly, the communication performance simulations demonstrated higher performance of forward access data capacity and transmission delay between navigation constellation and ground of the approach proposed, compared with the traditional satellite-earth fixed link. 
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    Design of controller for gravity unloading system based on neural network
    SUN Yibin, WANG Limei
    2021, 41 (1):  113-119.  doi: 10.16708/j.cnki.1000-758X.2021.0014
    Abstract ( 137 )   PDF (2373KB) ( 69 )   Save
    The hanging system is one of the important methods to simulate the gravity unloading experiment of a space manipulator on the ground. To overcome the shortcomings of slow response and poor robustness of traditional PID control modes, an intelligent control method based on radial basis function (RBF) neural network was presented. This method has strong non-linear fitting ability and simple learning rules.It can map any complex nonlinear relationship, and is convenient for computer implementation. Taking advantage of this feature, a controller with higher precision of gravity unloading than PID control was designed. The control model identified by the controller using orthogonal least squares method, updates the weight RBF neural network by using a gradient descent method under the mathematical model of the servo motor with load. Finally, the simulation image of Matlab was obtained by writing s-function. Compared with PID control method, the simulation results have fast response, strong robustness and higher accuracy of gravity unloading (98%).
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    Overall technology analysis and efficiency simulation of the deep space impactor
    MA Xin, ZHOU Qi, LI Mingtao, ZHANG Huisuo
    2021, 41 (1):  120-130.  doi: 10.16708/j.cnki.1000-758X.2021.0015
    Abstract ( 167 )   PDF (4481KB) ( 87 )   Save
    In order to impact the near-Earth asteroid 2016HO3 for scientific exploration, the "deep space impacting mission" and the present state of the deep space impactor were presented, the Hayabusa-2 deep space impacting mission was reviewed in detail, the scientific objectives of the deep space impactor with regard to China′s plan for future deep space missions to near-Earth asteroids were given. Through the deep investigation and analysis of the Hayabusa-2 impactor, the whole technology system of the deep space impactor which is based on explosively-formed projectile was obtained; the detailed technical analysis and technical connotation of the explosively-formed projectile, the safe and reliable explosion, the impactor separation, the impacting simulation and some other aspects were given systematically. The preliminary design of the deep space impactor for the near-Earth asteroid 2016HO3 was obtained. Through the impacting simulation, the results show that the diameters of impact craters vary from 32cm to 47cm with different impacting speed of 0.2cm/μs to 0.4cm/μs. The high resolution variation pattern of the diameter and depth of impact crater with different projectile thicknesses, impacting velocities, and projectile diameters were provided. This paper can provide technology support for the overall optimization of the deep space impactor.
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