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    25 August 2018, Volume 38 Issue 4 Previous Issue    Next Issue
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    A star pattern recognition method based on self-organizing map network and triangle algorithm
    LIU Yan, XI Hongxia, CAO Jun, QU Haibo, SONG Chongjin, CHEN Li, AN Junjie
    2018, 38 (4):  1-10.  doi: 10.16708/j.cnki.1000-758X.2018.0043
    Abstract ( 230 )   PDF (9011KB) ( 15 )   Save
    Triangle algorithm is one of the most classical and widely used method of star pattern identification, but it has short comings of large search range, redundancy match, weak anti-noise ability, and so on. Applying the neural network technology to the satellite image recognition, a new recognition method combined with the excellent classification ability of neural network technology and the reliable angular matching ability of the triangle algorithm was proposed. The feature vector sofeachguidestar constructed based on the distribution of the neighboring stars were used to train the SOM network of the star pattern recognition system so that the classification function was obtained. The network could identify the class of the unknown star by the feature vector. In the corresponding triangle database, the triangle algorithm was applied to find the matching triangle and identify the star map. Results of simulated identification show that the new method can reduce the star catalog, identify the star map fast and make the system more robust with respect to noise. In the whole sky identification, the average recognition time is less than 5ms, and the recognition rate is still as high as 99% when the noise standard deviation is 0.025.
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    Cubature Kalman filter based on event-triggered mechanism
    LIN Haoshen, LI Sijia, LIU Gang
    2018, 38 (4):  11-19.  doi: 10.16708/j.cnki.1000-758X.2018.0041
    Abstract ( 217 )   PDF (4285KB) ( 95 )   Save

    In order to balance the contradiction between the communication rate and the filtering precision of the networked nonlinear filtering system, two kinds of event-triggered mechanisms based on stochastic event-triggered and detected event-triggered were proposed respectively. The framework of cubature Kalman filter (CKF) was designed under two kinds of event driving mechanisms on account of nonlinear of system, and the mathematical description of the update process was deduced. Two algorithms of detected event-triggered CKF (DECKF) and stochastic event-triggered CKF (SECKF) were obtained. Finally, ECKF was applied to the space-based spatial target localization to examine the performance of itself. The results show that the position and velocity tracking accuracy of DECKF are 5.50% and 7.74% lower than traditional CKF when the communication rate had declined by 20.64%. On the other hand, the accuracy of the DECKF was above 40% higher than the SECKF under the same communication rate, which demonstrated the effectiveness of the DECKF.

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    Hybrid switching control method for micro-satellite station keeping
    YANG Bo, WEI Baojie, WEI Yanming, MIAO Jun
    2018, 38 (4):  20-26.  doi: 10.16708/j.cnki.1000-758X.2018.0021
    Abstract ( 67 )   PDF (4902KB) ( 70 )   Save

    Solid propellant micro-thruster array (SPMTA) as a new type of thrust device for micro-satellite station-keeping has the advantages of high accuracy, no fuel leakage and adjustable impulse. But the thrust of SPMTA is discontinuous, making the control system design different from the previous continuous system. To realize the full potential of SPMTA, a new control method for micro-satellite station-keeping was proposed based on the idea of switching control in hybrid system. First, the satellite discrete dynamic model was deduced according to the thrust characteristics of SPMTA. Then the hybrid switching control law was designed based on the Lyapunov stability theorem. Finally a numerical example of micro-satellite station-keeping was presented. Numerical simulation results indicate that the hybrid switching control method can accurately reflect the characteristics of SPMTA. The accuracy of station-keeping can reach 0.2 m and the consumption meets the satellite requirements of long time orbit operation.

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    Orbit reconstruction configuration of navigation constellation based on differentialevolutionalgorithm
    ZHAO Shuang, ZHANG Yasheng, DAI Huayu
    2018, 38 (4):  27-35.  doi: 10.16708/j.cnki.1000-758X.2018.0046
    Abstract ( 79 )   PDF (3878KB) ( 94 )   Save

    Aiming at the navigation constellation with satellite failure, a method of phase maneuvering on satellites in orbit is proposed to reconstruct the space configuration of the constellation in order to achieve the purpose of improving and recovering the constellation performance. Firstly, the phase of on-orbit satellites was adjusted by the method of phase maneuver of coplanar high orbit and coplanar low orbit, and the mathematical model of phase maneuver of coplanar orbit was set up; secondly, other reconstruction indexes besides reconstruction time and reconstruction energy were proposed, including the balance of reconstruction energy and the robustness of reconstruction configuration, and the mathematical model of each reconstruction index was established; then, an optimization model of the reconstruction configuration was established, and the evaluation method and coding method of the individual in the optimization problem were designed; finally, taking the failure of MEO satellite in Beidou as an example, the differential evolution algorithm is used to solve the optimization model, and the Pareto fronts with different reconstruction indexes as objective functions are obtained. It can be seen from the results that this reconstruction method can improve the constellation performance up to 41.2%, and in all reconstruction strategies corresponding to the Pareto front, the orders of magnitude of reconstruction energy, the balance of reconstruction energy and the robustness of reconstruction configuration were maintained at -1, -3 and the level of 0.

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    Intelligent fuzzy control algorithm of flexible spacecraft
    ZHANG Henghao, TANG Qingbo, YAN Ning, CHEN Chunyan, ZHENG Zhenglu
    2018, 38 (4):  36-43.  doi: 10.16708/j.cnki.1000-758X.2018.0026
    Abstract ( 205 )   PDF (5396KB) ( 103 )   Save

    Aiming at the problem about high frequency chattering caused by flexible spacecraft′s sliding mode variable structure control torque, an intelligent fuzzy control algorithm of flexible spacecraft was proposed. Firstly, fuzzy control algorithm and sliding mode control algorithm were combined, and the exponential approach law parameters were fuzzy based on the size of switching function and derivative of switching function. Secondly, the continuous saturation function to replace symbolic function in sliding mode variable structure controller was used. Finally, the boundary layer thickness was adjusted by the sliding mode boundary′s degree. As a result, the boundary layer thickness was controlled, and the problem about high frequency chattering was solved. Simulation results demonstrate that the algorithm can improve high frequency chattering obviously and flexible spacecraft′s vibration suppression can be accomplished with faster convergence.

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    On-orbit temperature field calculation and deploying opportunity analysis for large net-shape antennas′ deploying process
    LI Tao, XIAO Zhiwei, ZHANG Xiaoxiao
    2018, 38 (4):  44-50.  doi: 10.16708/j.cnki.1000-758X.2018.0040
    Abstract ( 163 )   PDF (15297KB) ( 22 )   Save

    The deploying process of large net-shape deployable antennas on orbit is complex and risky. The wide temperature of reflector is the key factor because it influences the deployment resistance and the bending capacity of carbon fiber tubes. The effect of temperature on the transmission efficiency and the bending capacity of carbon fibertubes was investigated by high and low temperature performance tests, and the results show that the bending capacity of carbon fiber tubes is best at -65℃, and that the transmission efficiency increases as the temperature rises.Finite element model and node matrix transit method were built for large net-shape deployable antennas, on-orbit temperature field of carbon fiber tubes and T-Joints in antennas′ deploying process were studied. The test result of the transmission efficiency and the bending capacity of carbon fiber tubes change with temperature, confirming antennas′ optimal deploying opportunity and reducing the risk of deploying power shortage and intensity overload. The analysis results indicate that with the large net-shape deployable atennas placed on the east panel of the geostationary satellite platform, the bending capacity of carbon fiber tubes is the strongest during 6:00~9:00 and that the transmission efficiency of T-Jointsis the highest at 4:00.

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    Motion characteristics of pointing mechanism with clearance in consideration of wear
    HAN Xueyan, LI Shihua, ZUO Yaming, LI Jun
    2018, 38 (4):  51-61.  doi: 10.16708/j.cnki.1000-758X.2018.0036
    Abstract ( 174 )   PDF (10017KB) ( 16 )   Save

    For the accurate prediction of the joint dynamic wear, the coupling factors of clearance, friction and abrasion were considered. The dynamic problems and abrasion problems of the twodimensional space pointing mechanism were studied, which considered the factors of clearance, friction and abrasion. Using the Newton Euler’s law, the dynamic model of the twodimensional space pointing mechanism with clearance was constructed by embedding the clearance variables. Based on the Archards wear model, by finding the wear depth at different positions of the moving contact surface and reconstructing the surface morphology of the kinematic pair, the dynamic characteristics of the pointing mechanism with clearance were analyzed in the process of wear, and the change laws of the contact collision force and the tangent friction force at the joints were obtained; the dynamic fitting variables method and the discrete processing method were used to fit the correspondences between the clearance and contact force, and the running time and the relative slip velocity of the kinematic pair with clearance, and  the dynamic wear mathematical model was established; furthermore, the predicted service lives of the two dimensional pointing mechanism are 12591.92 hours and 764.44 hours under the tracking mode and the attitude adjustment mode. The work in this thesis provided the theoretical base for the ontology design, manufacture and application of the two dimensional pointing mechanism.

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    Satellite constellation design for regional maneuvering target searching
    ZHAO Chengliang, ZHANG Zhanyue, LI Zhiliang, LIU Yao
    2018, 38 (4):  62-68.  doi: 10.16708/j.cnki.1000-758X.2018.0045
    Abstract ( 194 )   PDF (2450KB) ( 94 )   Save

    Aiming at imaging satellite mission planned for marine maneuvering target, a satellite constellation for maneuvering target in ocean area searching and monitoring is designed. Firstly, according to the characteristics of maneuvering target search task, a satellite image stitching search strategy considering spatio-temporal constraints was established. Secondly, according to the established maneuvering target search strategy, a high time resolution networking constellation configuration was designed. Finally, a robust model was constructed based on minimizing the side pendulum angle and the task observation time of the networking satellite as  the optimization target. The simulation results demonstrate that the satellite constellation can effectively monitor the target area, providing the support method for maneuvering target regional surveillance task.

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    Attitude maneuver strategy for zero Doppler beam center of fast response SAR satellite
    HE Rongrong, HE Baoping, FENG Fan, DANG Hongxing, Tan Xiaomin
    2018, 38 (4):  69-75.  doi: 10.16708/j.cnki.1000-758X.2018.0039
    Abstract ( 254 )   PDF (3878KB) ( 84 )   Save

    The attitude maneuver parameter is derived from six elements of satellite orbit in ECI for traditional yaw-steering method. Only the Doppler centroid frequency of satellite main axis is compensated to zero.The error slant range and Doppler centroid frequency drift arose by the installation error between antenna and satellite and the beam angle departing from coordinate axis in elevation and azimuth direction are not removed.The requirements of SAR system time order and on-board real-time processor of response SAR satellite isn′t satisfied. A new strategy of SAR antenna beam to target in zeros-Doppler plane of ECF was proposed so that Doppler frequency of beam center for fast response SAR satellite would be zero. Firstly, the accurate time order and look parameter was computed. Secondly, satellite’s three axes direction was derived from SAR beam’s three axes direction in ECF. Finally, the attitude maneuver parameters were obtained. The simulation results by Matlab show that applying the strategy to the fast response SAR satellite, the Doppler frequency 29 kHz of earth rotation, 360 Hz of installation error and 3950 Hz of the beam departing angle are compensated to 0 Hz.Simultaneously the slant error 6.28 km is compensated to meter level.

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    Satellitelife prediction method anditsapplication by multiple mechanisms
    ZHAO Haitao, YANG Hui, XIONG Xiao
    2018, 38 (4):  76-83.  doi: 10.16708/j.cnki.1000-758X.2018.0047
    Abstract ( 55 )   PDF (4921KB) ( 90 )   Save
    Based on the realistic requirement of satellite life prediction and the deficienciesin previous methods,anewlifeprediction methodconsidering multiple mechanisms wasproposed.The life characteristics of satellite products and the causes for the end of satellite life were analyzed. Considering random failure, a life prediction model updated with satellite operating timeand system components was proposed, and the method solving multi-stage distribution parameters wasgiven. Based on this, the random failure, degradationand exhaustion were considered synthetically, and a new life prediction method was built. A case study shows that the new method can be used to get the more depend able results, which are very important for the constellation maintenance strategy.
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