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25 August 2021, Volume 41 Issue 4 Previous Issue    Next Issue

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Overview of non-Keplerian displaced orbits by low-thrust propulsion PAN Xiao, XU Ming 2021, 41 (4):  1-15.  doi: 10.16708/j.cnki.1000-758X.2021.0046 Abstract ( 340 )   PDF (4502KB) ( 389 )   Save The non-Keplerian displaced orbits by low-thrust propulsion have significant applications in observation missions of the deep space and Earth polar region. The development of the continuous low-thrust propulsion technology represented by the electric propulsion and solar sail propulsion was detailed. The heliocentric and planetary displaced orbits were discussed to reveal the nonlinear dynamical characteristics, stability and orbit keeping strategies. The advantages of artificial Lagrangian points generated in the three-body problem were analyzed as well as its application in deep space explorations. Moreover, the relative dynamics and control of formation flying in displaced orbits were discussed. Finally, new research directions and applications were proposed for the research challenges of displaced orbits by low-thrust propulsion. Related Articles | Metrics

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Research status and prospect of modular space deployable and foldable mechanism TIAN Dake, GAO Haiming, JIN Lu, LIU Rongqiang, MA Xiaoou, FAN Xiaodong, GUO Zhenwei 2021, 41 (4):  16-31.  doi: 10.16708/j.cnki.1000-758X.2021.0047 Abstract ( 526 )   PDF (19796KB) ( 625 )   Save The modular space deployable and foldable mechanism has the characteristics of flexible expansion, good versatility and strong adaptability, which can meet the needs of large and ultralarge space deployable and foldable mechanism for major aerospace projects in China, such as long-distance deep space exploration, long-term in-orbit space station construction and ultra wide area satellite communication, and it is a new key aerospace equipment. According to the application requirements, the research progress of space modular deployable and foldable mechanism was described. The typical modular configurations of three types of deployable and foldable mechanism, such as deployable mast, solar array and space deployable antenna, were mainly introduced. The structure composition, deployment principle, driving mode and application status of modular space deployable and foldable mechanism were analyzed. The future development direction of space modular deployable and foldable mechanism was prospected from four aspects: mechanism innovative design method, ground microgravity test and simulation, space inorbit assembly technology and space inorbit construction technology. The review provides a reference for the research and application of large space deployable and foldable mechanism in China. Related Articles | Metrics

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Optical emission spectroscopy diagnostics of CO2 conversion with micro-plasma SUN Jianghong, SUN Surong, WANG Haixing, MA Tao 2021, 41 (4):  32-40.  doi: 10.16708/j.cnki.1000-758X.2021.0048 Abstract ( 218 )   PDF (6531KB) ( 452 )   Save The main component of the Martian atmosphere is CO2. If these CO2 can be efficiently converted into O2 and CO by low-temperature plasma for utilization, the launch load cost of life support system can be drastically reduced for deep space mission and the life support capabilities will be further improved. Low-temperature plasma shows a promising potential for CO2 dissociation and conversion. It can produce plenty of reactive species during the discharge, which enables the efficient CO2 conversion at a gas temperature of only a few hundred degrees. A DC microslit plasma reactor on submillimeter scale and with several Watts input power was designed, which can be used for the CO2 conversion at low gas temperature. The discharge parameters, such as discharge current and input power were measured. The optical emission spectroscopy (OES) method was adopted for identification of excited species and their variations with supply voltage and dilution gas content. The plasma vibrational and gas temperatures were measured based on the nitrogen vibrationrotation spectra. It is found that all of the three dilution gases (Ar, He, N2) can enhance the dissociation process, while adding helium gas can improve the CO2 ionization process. The excited species produced by dilution gases promote the CO2 dissociation through Penning dissociation channel because of their high energy. Since the excited state of helium (He*) has an energy higher than CO2 ionization threshold, it leads to an increase of CO2 ionization process. The nonequilibrium feature of microplasma was verified by large deviation between vibrational temperature (4400~4800 K) and gas temperature (450~600 K). Therefore, with reasonable plasma discharge and reactor structure design, the energy can be selectively injected into the vibrational species, which can further increase the CO2 vibrational dissociation. Related Articles | Metrics

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Preliminary analysis of unexpected electrical breakdown characteristics of LIPS-200 ion thruster ZHANG Xueer, ZHANG Tianping, LI Detian, MENG Wei 2021, 41 (4):  41-48.  doi: 10.16708/j.cnki.1000-758X.2021.0049 Abstract ( 352 )   PDF (3821KB) ( 343 )   Save Abstract： Unexpected electrical breakdown of the ion thruster directly affects the reliability of its engineering application. Based on the relatively complete data of breakdown events in the ground life test, a preliminary study was conducted on the breakdown phenomenon of LIPS-200 ion thruster in its 12000h life test with analysis approaches including data comparison, Weibull statistics and causal inference. Quantitative results were obtained, such as the average breakdown rate, the time distribution of breakdown events, the Weibull distribution of classified breakdown intervals. Analysis shows that the average breakdown rate of LIPS-200 is much lower than that of NSTAR and other products mainly because of its lower electrical field between grids; the distribution of breakdown events has a noticeable dependence on cumulative operating time; the characteristic breakdown intervals and breakdown rate change caused by different factors and mechanisms can be obtained with 2-parameter Weibull distribution model. Related Articles | Metrics

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Research on satellite multisource information Bayesian melding method XU Yingchun, ZHAO Shumin, CHONG Yuhai, CHEN Naisong, ZHOU Qian, ZHOU Tao 2021, 41 (4):  49-58.  doi: 10.16708/j.cnki.1000-758X.2021.0050 Abstract ( 258 )   PDF (3788KB) ( 160 )   Save There is a large amount of uncertainty in the development and operation of satellites, which directly affects the satellite performance and lifetime. How to realize the uncertainty modeling is an urgent problem, and the multi-source information integration is the key to uncertainty modeling. In addition, it is difficult to obtain the distribution information of the system directly due to the constraints of time and cost. To realize the multi-source information integration of satellite systems with a lack of information, the methods of the multilevel system structure modulization and the system information synthesization were put forward based on the traditional Bayesian melding method. Through the system structure decomposition, the information of lower levels was merged into the higher levels. Then with the induction inference method, the system node could get new information instead of non-information. Through a case study of a satellite attitude control system, the proposed method can make full use of the system structure relationship, effectively integrate and update the distribution information of each component and subsystem. The problem of missing system information is solved, which will provide reference for further development of the satellite system uncertainty design and optimization. Related Articles | Metrics

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Time and fuel constrained parameters autonomous optimization for variable-orbit sliding mode control ZHANG Han, KANG Guohua, ZHANG Qi, WEI Jianyu, DAI Jianfeng 2021, 41 (4):  59-68.  doi: 10.16708/j.cnki.1000-758X.2021.0051 Abstract ( 192 )   PDF (3928KB) ( 135 )   Save The relative motion orbit control of spacecraft adopts sliding mode control, which has good anti-disturbance performance, but the parameter setting is complicated. In order to be close to engineering reality, the fuel optimization constraint and optimization algorithm were introduced, and a parameter-based autonomous optimization sliding mode control that comprehensively considers time, fuel consumption and errors was proposed. Firstly, based on the linear relative motion equation and exponential approach sliding mode control, the relative motion sliding mode controller model was established, and the energy-optimized trajectory planner gave the convergence constraint time to achieve efficient maneuvering. Secondly, the constraints of the sliding mode control adjustable parameters，time and error in the device were analyzed, and parameter magnitude optimization rules were formulated. Finally, through inertia weight improved particle swarm algorithm, the least fuel consumption within the allowable error range was used as the optimization evaluation standard, and the output was the combination of superior level and coefficient control parameters. Thus the optimal control of sliding mode was realized. The simulation shows that: using the parameter combination obtained by the particle finder, the sliding mode deviation controller can make the position and velocity errors converge stably through the minimum fuel consumption within specified time, increasing the spacecraft's life in orbit. Related Articles | Metrics

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Computational methods of mass properties for liquid-filled spacecraft LI Qing, HUANG Jun, MIAO Yuanming, YU Hangjian 2021, 41 (4):  69-76.  doi: 10.16708/j.cnki.1000-758X.2021.0052 Abstract ( 207 )   PDF (7653KB) ( 92 )   Save Mass properties of liquid-filled spacecraft are important for flight dynamics modeling and control design. However, measuring devices for mass properties are usually applicable to measure the spacecraft mass properties of dry weight only. Mass properties of liquid-filled spacecraft can only be obtained by computational methods. How to take into account the inertial tensor of liquid in each tank is the difficult point in such engineering computation. Theoretical expressions for mass properties of liquid in an arbitrary shaped tank were derived in a general sense. The derivation was conducted for a fully filled liquid tank with no free liquid surface and a partially filled liquid tank with a free sloshing liquid surface of small amplitude respectively. A numerical method for computing the mass properties of liquid was proposed using 3D finite elements. As a verification example, the numerical solutions and the analytical solutions of mass properties of the liquid in a rectangular tank were compared, which confirmed the accuracy of the proposed method. As an application research, mass properties of a liquid-filled spacecraft were computed using different computational methods. Studies show that the traditional computational method which solidifies the liquid obtains obviously larger moments of inertia, while the proposed method is more correct in theory and more applicable in engineering. Related Articles | Metrics

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An improved asynchronous fusion algorithm for multisensor integrated navigation system LIU Lili, LIN Xueyuan, CHEN Xiangguang 2021, 41 (4):  77-84.  doi: 10.16708/j.cnki.1000-758X.2021.0053 Abstract ( 241 )   PDF (3940KB) ( 117 )   Save In order to solve the problem that the data sampling rate of each subnavigation sensor in the multi-sensor integrated navigation system is different and rational, an information fusion algorithm for the integrated navigation system was proposed. First, the original state equation of the multi-sensor integrated navigation system was transformed into the relationship between the state data block vector and the current state vector to form a new state equation, and the original measurement equation was expressed as the relationship between the state data block vector to form a new measurement equation. Then, based on the matrix operator with scale and small baud property, the concrete implementation process of the improved asynchronous fusion algorithm was given. Finally, the algorithm was applied to the multisensor integrated navigation system of CNS/GNSS/SINS/altimeter. The simulation results show that the position, speed and attitude accuracy can be improved by about 20%, 15% and 10% respectively, compared with the traditional algorithm. The high-precision characteristics and feasibility of the algorithm are verified. Related Articles | Metrics

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Design method of multi-level regional reconnaissance elastic constellation WANG Hao, ZHANG Zhanyue, ZHANG Haitao, JIANG Ping 2021, 41 (4):  85-94.  doi: 10.16708/j.cnki.1000-758X.2021.0054 Abstract ( 362 )   PDF (4923KB) ( 203 )   Save A design method of multi-level regional reconnaissance elastic constellations was proposed. The constellation design process was divided into three sub-constellation design steps according to region information until the whole constellation met the design requirements for all regional performance. Taking regions divided into 3 levels as an example, the constellation design requirements, design indicators and design steps were analyzed firstly. Then the relationship between the minimum resolution of the ground and orbital altitude was derived and the orbital altitude of different subconstellations was determined. Finally, the optimization models of basic constellation, subconstellation 1 and subconstellation 2 were constructed by considering orbital inclination, multisatellite launch and ascending nodal drift synchronization. The design case shows that the constellation designed with this method can meet the design requirements of regional coverage classification and elastic classification, which proves the effectiveness of the method. Compared with the design method of Walker constellation, the number of satellites required for multi-grade regional reconnaissance elastic constellation under the same design requirements is far lower than that of Walker constellation, which further proves the superiority of the proposed design method. Related Articles | Metrics

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Research on on-orbit construction reconfiguration method of LEO communication constellation based on fuel consumption balance LI Jiuyang, HU Min, WANG Xuyu, LI Feifei, XU Jiahui 2021, 41 (4):  95-101.  doi: 10.16708/j.cnki.1000-758X.2021.0055 Abstract ( 296 )   PDF (6406KB) ( 199 )   Save Aiming at the problem of onorbit reconstruction of low earth orbit (LEO) communication constellations, the characteristics of LEO communication constellations were analyzed, and four reconstruction indicators were proposed, namely global average coverage, fuel consumption balance, total reconstruction time and total reconstruction velocity increment. And then the reconstruction method to increase the orbit height was analyzed. The reconstruction was modeled and analyzed using the multi-objective evolutionary algorithm based on decomposition (MOEA/D). The results show that the model optimization results can obtain multiple sets of optimal solutions to form a Pareto front, and obtain a solution with the optimal fuel consumption balance. The total reconstruction time for the two failure modes is 3.6×105s, the variance of the velocity increment is 261.4m2/s2 and 293.4m2/s2. These solutions can restore the original coverage performance of the constellation and make the fuel consumption the most balanced. Related Articles | Metrics

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Separated active vibration isolation technology for ultra-quiet scientific satellite YANG Hongjie, LIU Lei, LI Xinguo 2021, 41 (4):  102-110.  doi: 10.16708/j.cnki.1000-758X.2021.0056 Abstract ( 263 )   PDF (4563KB) ( 304 )   Save Aiming at the special index requirement of microvibration spectrum integration of advanced payloads developed by quantum science experiments, time-frequency transfer experiments and other projects, a separate active vibration isolation approach was investigated. The separated vibration isolation approach divides a satellite into a payload module (PM) and a support module (SM). Considering the connection of flexible cables and limit springs between the two modules, the dynamic model was first established. Subsequently, a six-degree-of-freedom vibration isolation controller based on acceleration feedback was designed. Considering the electrical noise of the control and drive circuit, the vibration isolation performance of the payload module with respect to the support module was analyzed in the time domain and frequency domain. The simulation results show that the cumulative power spectral density (PSD) of the PM's acceleration within 0.5~200Hz is less than 2μgn after active vibration isolation. Finally, the influence of the controller parameters on the cumulative PSD of the payload module′s acceleration was analyzed. The separated active vibration isolation method provides a technical way for the vibration isolation of ultra-quiet scientific satellite. Related Articles | Metrics

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An onboard time acquisition method for spacecraft LAN Tian, GUO Jian, ZHANG Hongjun, DONG Zhenhui, WEI Yongquan 2021, 41 (4):  111-120.  doi: 10.16708/j.cnki.1000-758X.2021.0057 Abstract ( 183 )   PDF (5035KB) ( 126 )   Save The accuracy of onboard time acquisition directly affects the execution of autonomous functions of the spacecraft. The main challenge in accurately obtaining onboard time is the data race between time acquisition action and time maintenance action. When interrupt nesting leads to data race between the second interrupt and interrupts with higher priority, it is necessary to determine if the onboard time needs to be corrected in high-priority interrupts according to the nested status of the second interrupt. For the existing onboard time acquisition method suitable for high priority interrupt nested second interrupt scenario, the interrupt status provided by the processor is used to determine whether the second interrupt is nested or not, which makes the method not suitable for some processors. To solve this problem, an onboard time acquisition method that does not depend on the interrupt state was proposed. The time between two adjacent second interrupts was divided into period with interrupt nesting possibility and period without interrupt nesting possibility. In the period with interrupt nesting possibility, the time maintenance identification was used to determine if the acquired onboard time needed to be corrected. Compared with the existing methods, the proposed method is processor-independent, and the computational complexity is similar to that of the existing methods, which makes it applicable to a wider range of applications. The proposed method has been applied on several onboard computers of China Mars explorer and achieved the expected goal. It can provide reference for the subsequent spacecraft software design. Related Articles | Metrics

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Fault diagnosis of satellite attitude actuator based on recurrent neural network NI Ping, WEN Xin 2021, 41 (4):  121-126.  doi: 10.16708/j.cnki.1000-758X.2021.0058 Abstract ( 271 )   PDF (1259KB) ( 205 )   Save To solve the problem of actuator failure in satellite attitude control system, a fault diagnosis method based on recurrent neural network was proposed. The satellite attitude control system was modeled, fault analysis was carried out, continuous time fault data of star sensor and angular velocity gyro were collected. Six kinds of heterogeneous cyclic neural networks were designed to diagnose and classify the fault data, and the network effect was compared in terms of the network depth, feedback unit, activation function and training algorithm. The effect of deep loop neural network with GRU is better, the accuracy of fault diagnosis is 95.7%. The results show that, for time series satellite data, GRU and the recurrent neural network with a certain depth have better fault diagnosis effect. Related Articles | Metrics

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Intelligent extraction of multiple objects in island and reef images based on satellite remote sensing JIANG Zhijun, ZHANG Shuhao, XIAO Jinsheng 2021, 41 (4):  127-133.  doi: 10.16708/j.cnki.1000-758X.2021.0059 Abstract ( 247 )   PDF (6020KB) ( 323 )   Save Satellite remote sensing images have the characteristics of complex background, different object scales, different directions, and unclear texture. The mainstream object detection algorithms based on deep learning cannot be directly applied to target detection in satellite remote sensing images. RetinaNet was improved to make it suitable for satellite remote sensing images. First, a new feature fusion method was designed to fuse the feature maps output by ResNet50, so that the fused feature maps have both highlevel semantic information and lowlevel texture detail information. Then, in order to reduce the influence of the complex background of the remote sensing image on the object features, a feature perception module was designed to reduce the influence of noise on the feature map while enhancing the useful features. Images of ship, plane and storagetank in the DOTA dataset were selected for training and testing. Experimental results show that, compared with RetinaNet, the improved algorithm has increased the average accuracy of plane, ship and storagetank by 4.1%, 2.5% and 2.4% respectively. Experimental results based on real image data of GF-2 satellite show that the proposed algorithm can be used to intelligently extract multiple types of targets in island and reef images from satellite remote sensing. Related Articles | Metrics

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A loss function of road segmentation in remote sensing image by deep learning YUAN Wei, XU Wenbo, ZHOU Tian 2021, 41 (4):  134-141.  doi: 10.16708/j.cnki.1000-758X.2021.0060 Abstract ( 336 )   PDF (10321KB) ( 363 )   Save Traditional road segmentation based on spectral features or morphological algorithms has some disadvantages such as low precision and difficulty in determining the threshold value, and the existing methods in deep learning do not consider the characteristics of roads, only using general methods to segment roads. A deep learning loss function named morphological loss function with road unique trait was proposed. Firstly, the connectivity algorithm was used to divide the prediction results into several separated connected regions, and the ratios of the region area to the circumscribed circle area was calculated respectively. Then, the average value of regions was taken as the morphological loss function of this batch of training data. Finally, the morphological loss function was summed with the cross entropy loss function according to a certain proportion to obtain the final loss function. Through the comparative experiment on open remote sensing dataset, MIoU, ACC and F1-Score were all improved by the addition of morphological loss function. According to the prediction image, the predicted road was more continuous when morphological loss function was added. The morphological loss function proposed is an effective method to improve the accuracy of road segmentation in remote sensing. Related Articles | Metrics