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25 February 2023, Volume 43 Issue 1 Previous Issue    Next Issue

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Cloud detection methods for remote sensing images：a survey LIU Zili, YANG Jiajun, WANG Wenjing, SHI Zhenwei 2023, 43 (1):  1-17.  doi: 10.16708/j.cnki.1000-758X.2023.0001 Abstract ( 1439 )   PDF (3043KB) ( 2460 )   Save  The cloud cover in the optical remote sensing images will obscure the ground information in different degrees，which causes the blurring and missing of the surface observation information and greatly affects the imaging quality of remote sensing images.Therefore，the detection and evaluation of cloud cover in remote sensing images are the basis and key to further analyze and utilize remote sensing image information.Through sufficient investigation and summary，the development trend and representative work of cloud detection methods based on remote sensing images at home and abroad since the 1990s were combed.Cloud detection methods based on remote sensing images were divided into three categories：methods based on band threshold，methods based on classical machine learning and methods based on deep learning.Besides，the public datasets at home and abroad used in the related research on cloud detection were summarized，and the accuracy of some representative cloud detection methods was compared.In addition to the vanilla cloud detection method，the cloud/fog（haze）detection，cloud/snow detection，cloud shadow detection and cloud removal methods related to cloud detection were also briefly combed.Based on the review and summary of cloud detection work above，the existing problems and future development trends of cloud detection were analyzed and prospected. Related Articles | Metrics

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Domain control strategy for the large-scale satellite cluster LI Ning, YUE Chengfei, GUO Haibo, QIU Shi, CAO Xibin 2023, 43 (1):  18-28.  doi: 10.16708/j.cnki.1000-758X.2023.0002 Abstract ( 495 )   PDF (6485KB) ( 670 )   Save In large-scale satellite constellations，single node management and control will lead to poor system connectivity and high dependence on ground resources.A distributed domain control strategy for satellite constellations with hierarchical management，intradomain autonomy and dynamic maintenance was proposed.Firstly，both the static index and dynamic index to measure the governability were defined.According to the newly-defined indexes，a multi-factor weighted cluster head selection method was proposed.Then，based on the selected cluster head node，a cascading optimal initialization algorithm of the cluster was established.Aiming at dynamic maintaining of the established cluster control structure，an event-triggered dynamic time slice domain control method was proposed.Finally，control simulation result of the proposed method in the case of LEO large-scale satellite constellation verifies the effectiveness of cluster head selection，cluster initialization and long-time maintaining.The number of satellites which were managed through ground station was reduced to 14%.High dependence on ground resources was resolved. Related Articles | Metrics

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Satellite multi-object repetitive observation mission planning based on hierarchical clustering ZHANG Yaoyuan, YANG Hongwei, YUAN Ronggang, LIANG Yijin, LI Shuang 2023, 43 (1):  29-43.  doi: 10.16708/j.cnki.1000-758X.2023.0003 Abstract ( 308 )   PDF (5824KB) ( 329 )   Save  In order to solve the problem of large scale of feasible task execution sequences for agile satellite multi-target repetitive observation mission planning,we proposed a hierarchical clustering task planning method with time decoupling of task execution sequence.In this method,the observable windows and task execution windows in the planning process are taken as the clustering objects,and the task set is decomposed into a series of time-decoupled,small-scale sets according to the task attributes in the set by single clustering of the observable windows and multiple clustering of the task execution windows.Then,a search algorithm based on greedy optimization was used to plan the small-scale task sets generated by clustering between two task execution windows.Finally,the execution sequence of all tasks was obtained by combining the task planning results of each set.The simulation results indicate that the hierarchical clustering method can effectively reduce the global optimization complexity,eliminate the conflicts between different types of observation tasks,improve the quality of mission planning,and can perform repeated observation of multiple observation opportunities without reducing the coverage rate of the target points.The algorithm has good stability and can get planned results in a few seconds,which is suitable for satellite onboard autonomous mission planning. Related Articles | Metrics

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Cluster collision avoidance trajectory planning for modular spacecraft with optimal energy ZHAO Teng, KANG Guohua, TAO Xinyong, Xu Chuanxiao, WU Junfeng 2023, 43 (1):  44-52.  doi: 10.16708/j.cnki.1000-758X.2023.0004 Abstract ( 200 )   PDF (4000KB) ( 287 )   Save Aimed at solving the problems of large fuel consumption，imbalance and long timeconsumption in the application of traditional cluster aggregation algorithm in spacecraft cluster planning，an energy optimal clustered collision avoidance algorithm based on centripetal aggregation was proposed.Firstly，based on the relative motion equation of the cluster and the finitetime energy optimization model，the energy optimal model of adaptive centripetal aggregation was established by the algorithm.On this basis，for the problem of long time-consumption and collision，a cluster collision avoidance algorithm based on energy optimization was proposed.The safe distance vector between modules was used as the collision avoidance constraint，and the energy consumption was used as the clustering algorithm index.The simulation results show that the algorithm can adaptively select the center of cluster clustering，effectively avoid collision，reduce the total energy consumption of cluster aggregation and the imbalance of energy consumption between modules，so that the working fluid consumption is globally optimal，and the time consumption is only one ten thousandth of that of the conventional genetic algorithm.This algorithm provides an idea for rapid and safe clustering of clusters. Related Articles | Metrics

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Dynamics and experimental study of the shock effect of two-body tethered satellite system DUAN Fucheng, ZHANG Huibo, HOU Weijie, QIN Xiaogang, WU Xia, YANG Shengsheng 2023, 43 (1):  53-62.  doi: 10.16708/j.cnki.1000-758X.2023.0005 Abstract ( 183 )   PDF (6619KB) ( 138 )   Save In order to study the “shock effect” on the dynamics of the twobody rope satellite system，a flexible rope model based on the absolute nodal coordinate formulation（ANCF）and the equations of motion of the tethered satellite system were established.Firstly，the establishment process of the flexible rope model based on the ANCF was introduced，and the axial stiffness matrix，bending stiffness matrix and mass matrix of the flexible rope were fully considered in the simulation，which can retain the true characteristics of the rope system without increasing the amount of calculation.Finally，a 3-degree-of-freedom ground simulation experiment system of two-body rope satellite was built，and the verification experiment on a large air-floating platform with a specification of 20m×30m was carried out.The tension of the tether and the motion state of the sub-satellite during the final release phase and the initial recovery phase was analyzed in this experiment.The validation results indicate that the error of the tether tension is within 5% in the ground simulation test compared with the simulation experiment，which verifies the validity of the modeling method and the reliability of the experimental system，and provides support for the future development of the tether satellite and the ground experiment. Related Articles | Metrics

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Research on multi-satellite distributed passive coherent location method WANG Yuqi, WU Nan, ZHANG Xu, LIU Dan, WANG Haiqiang, HAN Xiaodong, ZHONG Xiaoqing, WANG Ningyuan 2023, 43 (1):  63-68.  doi: 10.16708/j.cnki.1000-758X.2023.0006 Abstract ( 225 )   PDF (3058KB) ( 268 )   Save Aiming at the insufficient accuracy of bearing-only location for the directional emitter，a multi-satellite distributed passive coherent location method was proposed.Firstly，the emitter was roughly located according to the strong signal received by the reference satellite.Then，the reference satellite signal was distributed to the adjacent satellite，and the cross-correlation search was carried out with the side lobe signal in the rough location range to solve the time difference.Furthermore，the precise location of the emitter was estimated by using the multi-satellite time-difference-of-arrival location method.Finally，the Cramer-Rao lower bound analysis of the proposed method was carried out.The method was verified by simulation experiments.Simulation results show that the method can effectively improve the location accuracy of the emitter when the SNR of weak signal ranges from -40dB to 0dB.The location error can quickly approach the Cramer-Rao lower bound. Related Articles | Metrics

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Spreading code authentication method for GNSS signals based on chip-level amplitude modulation YAN Tao, LI Tian, TIAN Ye, WANG Ying, BIAN Lang, MENG Yansong 2023, 43 (1):  69-78.  doi: 10.16708/j.cnki.1000-758X.2023.0007 Abstract ( 192 )   PDF (4745KB) ( 183 )   Save Signal authentication is the key technique to meet the security requirement of next-generation GNSS civil signals.Compared with navigation message authentication(NMA),the spreading code authentication(SCA)can achieve greater security.To avoid the influence on the non-authentication users,the spreading code authentication method based on chip-level amplitude modulation(CAM-SCA)was developed.The proposed CAM-SCA method introduced the authentication feature to the chip level of GNSS civil signal by amplitude modulation.To verify the effectiveness of the proposed method,the detection probability was analyzed with the help of theory and simulation,and compared with the Chimera method adopted by GPS L1C signal.The results show that the proposed CAM-SCA method has an improvement of 2.55-2.78dB in terms of detection performance.The research results can provide a reference for the design of the next generation high-security GNSS signal. Related Articles | Metrics

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Design and performance test of TY-1 micro propulsion system LI Jingguang, LIANG Zhenhua, LIAO Wenhe, ZHANG Xiang, ZHAI Hao, FENG Guojin, XU Gen 2023, 43 (1):  79-87.  doi: 10.16708/j.cnki.1000-758X.2023.0008 Abstract ( 172 )   PDF (4388KB) ( 204 )   Save In response to the technical requirements of the "Tianyuan-1（TY-1）" micro/nano satellite formation flight mission，the overall design of the micro propulsion system was carried out.Due to low specific impulse，high storage pressure and complex structure，the conventional cold gas propulsion is difficult to meet the requirements of micro/nano satellites.R134a was chosen as the propellant，and by liquefying the propellant the propulsion system volume can be reduced effectively.Based on the 3D printing technology，the storage tank，plenum chamber，and the pipe can be integratedly designed.To improve the system specific impulse，the heating nozzle was designed and manufactured by using MEMS processing technology.The thrust and specific impulse were analyzed under different nozzle sizes，gas pressure and jet temperature.Based on the analysis result，the nozzle design was confirmed.The heating nozzle characterization test shows that the error of manufacture is controlled under 2%.Under vacuum conditions，the thrust performance was tested by using torsion pendulum measuring system.The results show that this propulsion will produce thrust between 5 and 10mN if the pressure is controlled between 0.1MPa and 0.2MPa.Besides，the specific impulse will increase by 10% if the jet temperature is raised from 25℃ to 95℃. Related Articles | Metrics

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An improved fault diagnosis method for solid-liquid rocket engine WU Yifan, WEI Yanming, YANG Bo, YU He, LIU Chaofan, WEI Xiang 2023, 43 (1):  88-99.  doi: 10.16708/j.cnki.1000-758X.2023.0009 Abstract ( 178 )   PDF (7093KB) ( 104 )   Save Aiming at the reliability problem of solid-liquid rocket engine,an improved Bayesian network fault diagnosis system was designed,which can diagnose multiple faults of solidliquid rocket engine through networking autonomous logic reasoning.In order to extract the fault features of time series observation signals,a scheme combining the marching method with the kernel principal component analysis (KPCA) was proposed.And then based on the fuzzy c-means clustering algorithm (FCM),a fuzzy polymorphic Bayesian network was established to realize the fuzzy processing of the scale of observation signals,which improves the diagnosis ability of uncertain faults.The improved Bayesian network fault diagnosis system was established by Matlab/Simulink.The simulation results show that the improved algorithm can effectively diagnose the common faults of solid-liquid rocket engine,and can adapt to the condition of small sample set.Compared with the traditional Bayesian diagnosis algorithm,the average accuracy of fault diagnosis is improved by 20.9%. Related Articles | Metrics

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Motion modeling and gait planning of the leg-arm fusion robot for in-orbit assembly ZHU Li, LI Tuanjie, NING Yuming, YAO Cong 2023, 43 (1):  100-108.  doi: 10.16708/j.cnki.1000-758X.2023.0010 Abstract ( 257 )   PDF (7099KB) ( 237 )   Save In order to solve the problems of low efficiency，limited space operation and incomplete environment perception，a leg-arm fusion in-orbit assembly robot was proposed.Firstly，the kinematics model of the leg-arm fusion assembly robot was established by D-H method，and the forward and inverse kinematics of its legs were analyzed to obtain the motion relationship between each joint angle and the foot.Secondly，the walking gait and assembling gait of the leg-arm fusion assembly robot were analyzed.The two and three gait were analyzed in the walking gait，and the one-arm assembly and two-arm assembly were analyzed in the assembly gait，so that the robot could walk and assembly smoothly.Finally，a simulation platform based on ROS （robot operating system）was built and the effectiveness of the above walking gait was verified.The results show that the proposed method can be effectively applied to the walking of the robot. Related Articles | Metrics

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Vibration suppression of cable net antenna based on repetitive active disturbance rejection control DONG Yutong, WANG Wenhao, MA Xiaofei, LIU Lei 2023, 43 (1):  109-118.  doi: 10.16708/j.cnki.1000-758X.2023.0011 Abstract ( 175 )   PDF (7003KB) ( 223 )   Save In order to solve the problem of vibration suppression of cable net space antenna，an active vibration control method based on active disturbance rejection repetitive compound controller was proposed.At first，the vibration dynamic model of antenna surface was established by using finite element method.The model order was reduced based on modal truncation method.Then，based on the energy minimization criterion，the position of sensor/actuator was optimized by using genetic algorithm.Finally，the active suppression algorithm of antenna surface vibration based on linear active disturbance rejection control was designed，and the feedforward repetitive control algorithm was designed to improve the ability of the controller to suppress periodic disturbance by learning the periodic error of feedback control.The simulation results show that the proposed control method can reduce the profile disturbance by 97.0%，and the control effect is better than PID controller.The designed control method provides a new technical approach for the vibration control of antenna mesh surface. Related Articles | Metrics

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Design and performance analysis of scissors telescopic vertical rod hoop truss mechanism YU Liwei, HE Baiyan, NIE Rui, FAN Yesen, MA Xiaofei 2023, 43 (1):  119-128.  doi: 10.16708/j.cnki.1000-758X.2023.0012 Abstract ( 185 )   PDF (8364KB) ( 328 )   Save The deployment smoothness is the key to the smooth deployment of space deployable antennas.The fold/deployment ratio of the antenna is a vital reference factor for the spatial configuration of launch vehicles.To reduce the vibration and shock during the deployment process，improve the deployment smoothness，and reduce the fold/ deployment ratio，the common configurations of deployable antenna truss mechanism were combed.A kind of scissors telescopic vertical rod hoop truss mechanism was proposed，and the basic unit and deployable method were introduced in detail.A detailed analysis of the fold/ deployment ratio shows that the height-to-diameter ratio of the mechanism was reduced by about 35% compared with the Astromesh antenna truss mechanism under the same caliber and deployment height.Through kinematics and dynamics modeling，the deployment smoothness of the mechanism was analyzed.The results indicate that under the same driving force，the root mean square value of the acceleration at each node is about 30% of the Astromesh antenna truss mechanism，with better deployment smoothness.A scaled model was developed.The experimental analysis and parameter test were carried out，demonstrating rationality of the designed mechanism and accuracy of the calculation results. Related Articles | Metrics

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Configuration design and optimization of deployable membrane sunshield for spacecraft PENG Tao, LIN Qiuhong, LI Bingyan, QIU Hui, LIU Rongqiang, LUO Ani 2023, 43 (1):  129-138.  doi: 10.16708/j.cnki.1000-758X.2023.0013 Abstract ( 171 )   PDF (7453KB) ( 293 )   Save In response to the current demand for lightweight spacecraft sunshield,a flexible flat membrane sunshield was designed based on the mass and the effective area ratio on the premise that the effective area of the membrane sunshield remains unchanged.In order to improve the edge stress of the membrane while avoiding the reduction of the effective circle area,the edge of the membrane sunshield was optimized for arc design.The results show that when the thin-membrane sunshield is a regular hexagon,the symmetry of the structure can be ensured,and the minimum mass corresponding to the percentage of unit effective area can be obtained.The stress distribution model of the membrane sunshield was established with the stress superposition method,and the theoretical calculation value of the membrane edge stress was obtained.The influence of the increase of arc edge arch height on the membrane edge stress and the effective circle area ratio was explored.When the two function curves intersect at a point,the optimal arch height of the membrane arc edge can be selected.According to the designed parameters of the thin membrane sunshield,a test prototype of the thin membrane sunshield was built and the tensile experiment was performed.The edge tension of the membrane is high,which proves that the arc edge design plays an important role in improving the stress and stiffness of the membrane. Related Articles | Metrics

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Structural design of deployable parabolic cylindrical truss-mesh antenna reflector WANG Xiaokai, LI Xianghua, DU Jianghua, LIU Tianming, ZHONG Hantian, Chen Chuanzhi, LI Ming, ZHOU Xin 2023, 43 (1):  139-145.  doi: 10.16708/j.cnki.1000-758X.2023.0014 Abstract ( 258 )   PDF (6029KB) ( 353 )   Save For the requirement of the spaceused largesize cylindrical working surface,a deployable parabolic cylindrical truss-mesh antenna reflector constructed by quadrangular prism modular was proposed.The deploying and folding process of the parabolic cylindrical truss-mesh antenna reflector was realized by the driving assembly of the modular truss.The fitting method of parabolic working surface was extended to the parabolic cylindrical surface.The key design nodes of the support deployable struts were obtained by the radial projection of the uniform distributed nodes in the fitting circle.The front net nodes in the parabolic curve and the rear net nodes in the proposed catenary were obtained by the same method.Based on the front net nodes and rear net nodes,topological configuration of the parabolic cylindrical cable-nets was constructed.The pretension optimization design was performed by using the no-linear element method.The optimization results indicate that the maximum error ratio of pre-tension in the parabolic direction to its average value was 12.3% and the maximum error ratio of pre-tension in the cylindrical direction to its average value was 7.6%.Finally,a prototype with the size of 12m×12m was developed.Deployment tests and shape measurements were performed,and the parabolic cylindrical surface errors were tested within 2mm RMS.The results show that the proposed deployable parabolic cylindrical trussmesh antenna reflector has excellent deploying performance and a high surface precision. Related Articles | Metrics

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A method of misalignment error of space antenna harmonic reducer ZHANG Zhi, LIANG Yun, YAO Pei, NIU Baohua, AI Yongqiang 2023, 43 (1):  146-152.  doi: 10.16708/j.cnki.1000-758X.2023.0015 Abstract ( 141 )   PDF (4994KB) ( 126 )   Save The harmonic reducer used in aerospace requires high transmission accuracy，and the error caused by the misalignment problem of the reducer cannot be ignored.Therefore，the fault feature extraction method of the misalignment problem of the harmonic reducer has become the focus of the research.A new method termed optimal variational mode decomposition（VMD）was proposed to extract harmonic reducer misalignment fault features.Firstly，since envelope entropy is very sensitive to fault signal features，it is used as a fitness function，which is an objective function for the whale optimization algorithm（WOA）.Secondly，WOA has numerous merits such as simple operation，fewer adjustment parameters and a strong ability for jumping out of local optimum，and is applied to the optimization of VMD.Finally，intrinsic mode function components were processed through a Teager energy operator.The suggested approach was employed to analyze the experimental signal collected from harmonic reducer.The comparison results show that the advanced method is more effective and demonstrates superiority over empirical mode decomposition，local mean decomposition and wavelet packet decomposition. Related Articles | Metrics