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25 April 2015, Volume 35 Issue 2 Previous Issue    Next Issue

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Feature Extraction and Distribution Test for Orbit Residuals in Beidou Navigation Satellite CHEN Lue, TANG Ge-Shi, CUI Hong-Zheng, CHEN Ming, LIU Hui-Cui, WANG Mei 2015, 35 (2):  1.  doi: 10.3780/j.issn.1000-758X.2015.02.001 Abstract ( 1679 )   PDF (548KB) ( 1848 )   Save To analyze the no-modeling system error of orbit residuals in COMPASS, the orbit residuals feature extraction method with the ensemble empirical mode decomposition (EEMD) and Hilbert spectrum was proposed, and the normal distribution character of the orbit residuals chi-square test was analyzed. Firstly, the feature extraction principle of EEMD and Hilbert spectrum was introduced, the EEMD method assisted by the filter was proposed, and the feature extraction model of orbit residuals was established. Secondly, the feature of Pseudo-range and carrier phase orbit residuals in COMPASS was analyzed. Finally, the EEMD and Hilbert spectrum method was applied to analyze the Beidou GEO satellite orbit residuals. The results show that EEMD and Hilbert method can accurately extract the features of 1 day period, which is related to Beidou orbit running period. The chi-square value of the post orbit residuals obtained by EEMD is 5.5, which is smaller than the critical value of chi-square test. It proves that the post orbit residuals are normal distribution. The proposed method is important for separating the no-modeling system error in Beidou navigation satellite orbit residuals to improve the orbit determination precision. Related Articles | Metrics

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SINS/GPS/CNS Multi-integrated Navigation System Algorithm inLaunch Inertial Coordinate System and Realization PAN Jialiang，XIONG Zhi，ZHAO Hui， YU Feng，WANG Lina 2015, 35 (2):  9.  doi: 10.3780/j.issn.1000-758X.2015.02.002 Abstract ( 1474 )   PDF (476KB) ( 1629 )   Save A single integrated navigation system cannot meet the long-endurance high precision requirement of space long-range missile, so a SINS/GPS/CNS multi-integrated navigation system in launch inertial coordinate system was designed. Firstly, an integrated navigation model was built in the launch inertial coordinate system. Secondly, a SINS/GPS/CNS integrated navigation algorithm based on the federal Kalman filter was designed. Finally, an integrated navigation algorithm verification prototype based on PC104 was developed. Through the real time semi-physical simulation tests, the attitude error of triple integrated navigation system is below 15″, the position error is below 10m and the velocity error is below 0.2m/s. It indicates that the integrated navigation system algorithm designed is right and the realization of the system is reasonable. Related Articles | Metrics

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Road Extraction Algorithm for High Resolution SAR Image byFusion of MRF Segmentation and Mathematical Morphology CHEN Li-Fu, WEN Jun, XIAO Hong-Guang, PANG Ke-Chen 2015, 35 (2):  17.  doi: 10.3780/j.issn.1000-758X.2015.02.003 Abstract ( 1102 )   PDF (618KB) ( 1127 )   Save Related Articles | Metrics

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Longitudinal Flight Performance Analysis ofParafoil-payload Systems CHEN Jian-Ping, ZHANG Hong-Ying, TONG Ming-Bo 2015, 35 (2):  25.  doi: 10.3780/j.issn.1000-758X.2015.02.004 Abstract ( 1405 )   PDF (412KB) ( 1592 )   Save Flight performance of parafoil-payload systems is not only dependent on the aerodynamic characteristics of the parafoil itself, but also closely related to the system parameters such as rigging angle, rope length, drag force characteristics of the payloads and wing loads. The longitudinal flight dynamic equations of a parafoil-payload system were developed by adopting Lagrange equations and used to compute the flight response of the parafoil-payload system. With the aerodynamic characteristics of the parafoil given, the effects of the system parameters and opening state on longitudinal flight performance were discussed. The results show that only the rigging angle is within 0°~20°, the parafoil-payload system can reach a steady state of glide. Furthermore, the rigging angle within 4°~6° corresponds to two steady states of glide, which is dependent on the opening pitching angle and the opening velocity of the system. Increasing the rope length will make the system static stability increased. The more the drag force characteristics of the payload, the more the glide angle of the parafoil-payload system. With the drag force characteristics of the payload increased 6m2, the glide angle of the system increases about 15°, while the attack angle decreases less than 1°.In addition, wing loads have significant influence on the flight speed of the system. The speed of a parafoil-payload system is increased with the increase of wing loads and the square of the speed is proportional to the mass of the payload. These conclusions can provide theoretical guidance for practical application of parafoil-payload systems. Related Articles | Metrics

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Influence of Structural and Mechanical Parameters inDiagonal Component on the Performance ofADAM-type Articulated Mast LI Biao, LIU Zhi-Quan, CHENG Gang, DING Feng 2015, 35 (2):  33.  doi: 10.3780/j.issn.1000-758X.2015.02.005 Abstract ( 1151 )   PDF (441KB) ( 1663 )   Save The influence of the diagonal structural parameter (the angle between the diagonal cable and the batten) on the mast shear stiffness and the torsion stiffness was analyzed. An optimization range of the angle was obtained to determine the batten length. The minimum and maximum value of preloads of diagonal cables were obtained based on the rules that the loads on rods would be less than the allowable buckling stress and the mast wouldn’t collapse on orbit. The relationship between the preloads of diagonal cables and contact stiffness of spherical joint was obtained by the Hertz contact theory and the Winkler beam base hypothesis. Afterward, considering the relationship, the modal analysis was carried out with a finite element model of a mast bay. The analysis results show that the fundamental frequency would increase as the preload increases first, and then the frequency would decrease. Also, the optimization range of preloads in test model is between 500 to 700N. The relationship between the maximum torsion during deploying/retracting and latch/unlatch force was obtained by static analysis and ADAMS simulation, the results of static analysis and ADAMS simulation is consistent. Then the maximum torsion test during deploying/retracting was carried out. By comparing with the test data, the error of the static analysis results and the ADAMS simulation one is less than 3%. Related Articles | Metrics

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Design and Analysis of Non-cooperative TargetDrag-and-drop Docking Mechanism Li-Long-Qiu, LIU Wei-Min, CHEN Meng, ZHANG Guang-Yu, ZHANG Xue-Min, BAI He-Min 2015, 35 (2):  41.  doi: 10.3780/j.issn.1000-758X.2015.02.006 Abstract ( 978 )   PDF (489KB) ( 1515 )   Save According to the requirements of the non-cooperative target docking technology, a type of non-cooperative target drag-and-drop docking mechanism was proposed. The drag-and-drop docking mechanism is more reliable compared to the previous docking mechanisms. A three-dimensional model of the drag-and-drop docking mechanism was established. The range of the envelope space of the docking mechanism was determined. Kinematics and dynamics simulations were performed for the docking mechanism using the ADAMS software, to identify the dynamic characteristics of the docking process between the target satellite and the docking mechanism, and the capture force and the stress on the joints in the docking process. The simulation results show that the drag-and-drop docking mechanism can capture the target satellite effectively and reliably, and is suitable as a potential non-cooperative target docking mechanism. Related Articles | Metrics

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An Improved Strength Pareto Evolutionary Algorithm Based onthe Limited K-Nearest Neighbor Method JIANG Hong, YANG Meng-Fei, YU Guang-Liang, WEI Meng-Jie 2015, 35 (2):  49.  doi: 10.3780/j.issn.1000-758X.2015.02.007 Abstract ( 1192 )   PDF (466KB) ( 1765 )   Save In the process of Hardware/software co-design of spacecraft control computers, the multi-objective optimization is a key problem. The current strength Pareto evolutionary algorithm has some advantages in solving high-dimensional multi-objective optimization problems, but the computing time-complexity during the step of environmental selection is still very large. Aiming at this point, an improved algorithm was proposed. With the finite K-nearest neighbor method, new algorithm reduces the number of comparisons to lower the time-complexity from O(M3) down to O(max(l,logM)M2 . The experimental results show that the proposed algorithm not only improves the running speed, but also acquires better convergence and distribution diversity than the original one. Related Articles | Metrics

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Sunlight Avoidance Design for Camera of Geostationary Orbit Remote Sensing Satellite PENG Zhou, LI Zhen-Song, QIAO Guo-Dong, LIU Xin-Yan 2015, 35 (2):  57.  doi: 10.3780/j.issn.1000-758X.2015.02.008 Abstract ( 1174 )   PDF (407KB) ( 1855 )   Save It is very important for the optical imaging camera of the geostationary remote sensing satellite to avoid sunlight during its operation in orbit. To overcome the overlarge initial angular velocity in most attitude maneuver algorithms, the optimized attitude maneuver algorithm was proposed for the rolling shaft, based on the design of avoid angle remain. The angle remain was designed at the beginning or end of sunlight avoidance.To establish the initial state of the maneuver the process changes from the moment of achieving the sunlight avoidance angle to the angle remain. This increases the time of establishing the initial state and decreases the initial angular velocity. The experiment results show that the optimized algorithm is simple and reliable, the initial angular velocity reduces from 0.2(°)/s to 0.014(°)/s, and the attitude is stable during sunlight avoidance. Related Articles | Metrics

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Sliding-mode Attitude Controller Design for a Kind ofSpacecraft with Fuel Slosh〖ST〗〖WT〗 DU Hui, HAO Jin-Hua, XING Lin-Feng, LI Ya-Qiang 2015, 35 (2):  63.  doi: 10.3780/j.issn.1000-758X.2015.02.009 Abstract ( 1032 )   PDF (351KB) ( 1420 )   Save An incremental sliding-mode control design method was proposed for a kind of spacecraft with fuel slosh. The whole system was divided into two parts. The incremental sliding-mode control method was mainly used for the states which are not relative equilibrium ones. Two state variables of a subsystem were chosen to construct the first-layer sliding surface, and then the first-layer sliding surface and one of the left state variables were used to construct the second-layer sliding surface. Using the Lyapunov method, a sliding-mode control law can be derived. When the states reach the equilibrium position, the incremental sliding-mode controller was degraded into the monolayer controller which ensured the system stabilized at the uppermost equilibrium position within 30 seconds. Simulation results are given to illustrate the validity. Related Articles | Metrics

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Optimization of LIPS-300 Ion Thruster Accelerator Voltage CHEN Juan-Juan, ZHANG Tian-Ping, JIA Yan-Hui, WU Chen-Chen 2015, 35 (2):  70.  doi: 10.3780/j.issn.1000-758X.2015.02.010 Abstract ( 1377 )   PDF (457KB) ( 1231 )   Save Accelerator voltage directly affects the electron back streaming and acceleration grid sputter erosion. Therefore, how to obtain the best values of accelerator voltage is important for an ion thruster. The semi-empirical analysis method combined with the numerical simulation was used to analyze the equilibrium evolution of the beam current extracted from the LIPS-300 ion thruster grid and the grid lifetime was calculated. By using the numerical model, the sputter erosion rate that CEX sputtered on the surface of the acceleration grid was obtained. Then applying this erosion rate to the theoretical model, the lifetime of the LIPS-300 ion thruster was estimated and the failure modes for the five different accelerator voltages were analyzed. The results show that the change of the accelerator voltage would not affect the performance of the LIPS-300 ion thruster gird. For the LIPS-300 ion thruster, the downstream of the acceleration grid would be more vulnerable to CEX sputtering erosion. While the accelerator voltage is changed from -220V to -190V, the key failure modes of the LIPS-300 ion thruster gid is electron back streaming failure. By comparing the lifetime of the grid for the five different accelerator voltages, the best voltage is -220V and the corresponding lifetime is 16170.4h. Related Articles | Metrics

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Research on Denoising Method for Small PipeUltrasonic Flow Meter WEN Wen, ZONG Guang-Hua, YU Yang, SUN Liang 2015, 35 (2):  77.  doi: 10.3780/j.issn.1000-758X.2015.02.011 Abstract ( 972 )   PDF (477KB) ( 1574 )   Save The noise will directly affect the accuracy of the ultrasonic flow meter. The sources of noise inside the small pipe ultrasonic flow meter were analyzed. Considering the critical real-time measurement for the flow meter, a method of directly denoising the transit-time difference data was proposed. It avoided sampling and analyzing the original ultrasonic signal, which might lead to the poor performance of real-time measurement. For different noise sources, two different kinds of filters were applied. The wavelet filter was chosen as the first denoisng filter, which used a hard thresholding to reduce error from the random noise. A median filter and a mean filter were combined as the second denoisng filter to reduce error from the acoustic noise. The flow rate measurement experiment was implemented to verify the validity of the proposed denoising method. The results show that the instantaneous measurement error can be less than 1% after denoising. Related Articles | Metrics