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25 March 2018, Volume 38 Issue 2 Previous Issue    Next Issue

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A position calculating method of binocular vision based on datum optimization YANG Guanglie, ZHAO Guowei, LUO Kun 2018, 38 (2):  1-8.  doi: 10.16708/j.cnki.1000-758X.2018.0007 Abstract ( 300 )   PDF (22362KB) ( 31 )   Save Aiming to the requirement of relative attitude and position measurement in near-field for space non-cooperative target, position measurement model and error analysis model of characteristic point were established based on the theory of binocular vision. The problem of error increasing due to calculation singularity was analyzedas well. Based on aproposed optimization strategy, a characteristic point calculation method was founded for binocular vision system with non-coplanar optical axes. This method avoids the simultaneous singularity under both cameral datum by configuring the optical axes with certain alternate angle. According to the different measrement error distribution of each datum, the datum optimization strategy was established and the parameter determining method of corresponding criterion was proposed to obtain high precision measurement results. The numerical simulation result shows that, the proposed method can solve the calculation singularity problem and improve the precision of characteristic point position measurement in specific measurement domain. Related Articles | Metrics

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Routing optimization method for fast return of data on overseas satellites in Beidou Global Navigation Satellite System GAO He, WANG Ling, HUANG Wende, SUN Leyuan 2018, 38 (2):  9-15.  doi: 10.16708/j.cnki.1000-758X.2018.0002 Abstract ( 359 )   PDF (4539KB) ( 329 )   Save In order to solve the problem of the lack of station in Beidou Global Navigation Satellite System, a route optimization method was proposed to quickly transmit the overseas satellite data to the domestic satellite by using the inter-satellite link. Firstly, the problem of fast data transmission in the case of limited number of ground stations was described, and the optimization objective, rules and constraints of data transmission routing were defined. Then, based on the genetic algorithm, the routing optimization method and the minimum data transmission scheme were proposed. Finally, the validity of the algorithm was verified. The results show data transmission is completed within 2 skips (6 seconds) in the Beidou system constellation with two domestic station conditions. This optimized result can meet the requirements of overseas data fast transmit. Related Articles | Metrics

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Attitude determination algorithmfor micro-satellite based on Gauss-Newton and UKF KANG Guohua, FAN Kai, ZHOU Qiongfeng, LIANG Ertao 2018, 38 (2):  16-23.  doi: 10.16708/j.cnki.1000-758X.2018.0017 Abstract ( 284 )   PDF (11249KB) ( 65 )   Save To improve the attitude determination accuracy of miniature low-cost attitude sensor, a micro-satellite attitude determination algorithm combining Gauss-Newton iterative algorithmandunscented Kalman filter (UKF) was designed based on the attitude sensor configuration of magnetometer/solar sensor/gyroscope. Firstly, the Gauss-Newton algorithm was used to fuse the data of magnetometer and solar sensor, and the optimal quaternion was obtained. Secondly, UKF was performed using the optimal quaternion combined with gyrodata as the observed data, using the attitude quaternions and the angularvelocity of theinertial systemas the state variables, and the observed dimension was reduced and the observation equation was transformed into a linear equation by this method. As a result, the computational complexity is significantly reduced and the influence of measurement error on attitude determination accuracy is overcomed. Related Articles | Metrics

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Research on quadratic curveI GM for multi-terminal constraints SHI Guoxing, LYU Xinguang, GONG Qinghai 2018, 38 (2):  24-31.  doi: 10.16708/j.cnki.1000-758X.2018.0010 Abstract ( 356 )   PDF (2979KB) ( 139 )   Save Some space load has a high demand for the accuracy of orbit and flight attitude, and the accuracy of the perturbation guidance method applied in the launch vehicle cannot meet its requirements. The traditional iterative guidance method (IGM) cannot restrain the terminal attitude. Therefore, one quadratic curve IGM which satisfies the multi-terminal constraint was proposed. The method was used to plan the flight guidance program angle of the whole vacuum section through the quadratic curve, which satisfies the position constraint, velocity constraint and terminal attitude constraintinrealtime, making the attitude angle of rocket achieve high precision orbital parameters. Results show that the quadratic curve IGM can guarantee the high accuracy parameters of the orbit and the attitude of the orbit, and can adapt to the deviation states, the varieties of the constraint attitude angle and the number of the orbital parameters are slightly changed, and it has high engineering application value. Related Articles | Metrics

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Composite gait optimization method for a multi-legged robot based on optimal energy consumption ZHANG Shijun, XING Yan, HU Yong 2018, 38 (2):  32-39.  doi: 10.16708/j.cnki.1000-758X.2018.0023 Abstract ( 161 )   PDF (3892KB) ( 211 )   Save In order to study the effect of gait parameters, swing foot trajectory and body trajectory on gait stability and energy consumption of multi-legged robot a composite gait optimization method for a multi-legged robot based on optimal energy consumption was proposed，which transformed the gait optimization process into two nested sub optimization problems. Firstly，a body trajectory planning method based on zero moment point stability theory was given. The body trajectory was planned according to the next footholds and the supporting polygon. The body trajectory was continuous, smooth and stable with respect to the zero moment Point (ZMP)  stability theory. Secondly, a periodic gait optimization method based on energy consumption index was proposed. In order to optimize the walking gait, the virtual prototype model of quadruped robot was established as the gait optimization model, and the gait parameters，the swing foot trajectory and the body trajectory were optimized simultaneously. Finally，the virtual prototype simulation platform of the quadruped robot was built，and the simulation results show that the energy consumption of the robot is reduced by about 14% through the gait optimization algorithm. Related Articles | Metrics

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Research on radiative transfer chain for proper satellite radiometric calibration CHEN Xuan, QI Wenwen, XU Peng 2018, 38 (2):  40-46.  doi: 10.16708/j.cnki.1000-758X.2018.0009 Abstract ( 253 )   PDF (4815KB) ( 221 )   Save In order to further improve the quantitative application of remote sensing information and increase on-orbit radiometric calibration accuracy and frequency, an absolute radio metric calibration method of full-band, full-aperture based on proper satellite was presented. The method is suitable for the visible-near infrared spectrum, and the radiation standard in the radiative transfer has the SI-traceability. By comparing the advantages and disadvantages of the existing calibration methods, and the proper satellite radiometric calibration, the radiation standard traceability of the proper satellite was analyzed and the radiative transfer model from the sun to the proper satellite, then to the remote sensor was established. Taking GF-1 and GF-2 satellites as remote sensors under calibration, the simulation of the calibration constraints was acquired and the uncertainty of the proper satellite radiative transfer is about 1.3%. The simulation results verify the feasibility of the proper satellite calibration and provide a basis for the improvement of the radio metric calibration for the satellite remote sensors. Related Articles | Metrics

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Study of support vector machine based faults diagnosis for satellite′s actuators CHEN Xin, WEI Bingyi, WEN Xin 2018, 38 (2):  47-55.  doi: 10.16708/j.cnki.1000-758X.2018.0013 Abstract ( 231 )   PDF (2090KB) ( 139 )   Save For fault problems of micro-nano satellite attitude control system using pulsed plasma thruster as the actuator, the support vector machine technology was used to detect and isolate two kinds of common faults of pulsed plasma thruster. The wavelet kernel function parameters of Mexico hat were optimized by adaptive genetic algorithm (AGA). Combined with wavelet analysis, the hyperplane optimization efficiency and generalization ability of SVM classifier were improved by these methods. Finally, the experimental results prove that the method can accomplish fault diagnosis tasks quickly and accurately, and also prove the superiority and effectiveness of wavelet kernel function support vector machinesin fault diagnosis. Related Articles | Metrics

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Influences of heat load and feed water pressure on the start-up and operation strategy of sublimator WANG Yuying, NING Xianwen, ZHONG Qi, MIAO Jianyin, LYU Wei, WANG Lu, LIU Chang, LI Jindong 2018, 38 (2):  56-62.  doi: 10.16708/j.cnki.1000-758X.2018.0011 Abstract ( 178 )   PDF (7812KB) ( 32 )   Save Heat load, feed water pressure and other factors influence the vapor-solid-liquid phase change interfaces during the start-up and work processes, and this will affect sublimator's work stability and operation strategy. Experiments on sublimator start-up with both low thermal load and low feed water pressure, and start-up with both high thermal load and high feed water pressure conditions were carried out to study the Influences of heat load and feed water pressure on the start-up and steady-state work performance of sublimator. At the same time, a two-step experiment on sublimator was also carried out and the temperature responses of sublimator were tested. Start-up sublimator with low heat load and low feed water pressure achieved a steady state at first, and then both the thermal load and feed water pressure were increased to a large value. The experimental results revealed that: 1) Sublimator start-up with high thermal load and high feed water pressure reaches the steady-state in a shorter time, but this will increase the risk of breakthrough in start-up process. 2) Due to the advanced self-adjust capability of the liquid-solid-gas interface location in sublimator, a new balance will be established quickly. This indicates that the risk of breakthrough can be decreased through starting the sublimator in low thermal load and low feed water pressure. Increasing the thermal load and feed water pressure after it reaches the steady state to decrease the risk of "breakthrough", it will not influence the heat rejection performance. Related Articles | Metrics

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Dynamic characteristics simulation analysis for parachute-vehicle system of Mars Pathfinder LU Yuanyuan, RONG Wei, WU Shitong 2018, 38 (2):  63-70.  doi: 10.16708/j.cnki.1000-758X.2018.0030 Abstract ( 240 )   PDF (8565KB) ( 27 )   Save So far, the dynamic characteristics of parachute-backshell-lander three-body system for Mars Pathfinder during deceleration descending process have not been studied in China. To master the dynamis characteristics of the Mars Pathfinder parachute-payload system during descending, using the method of multi-body dynamics，an end-to-end dynamic model including parachute deployment, inflation, parachute filling, heat shield separation lander separation from backshell was proposed. The dynamic characteristics of the parachute-vehicle system for Mars Pathfinder during deceleration descending were studied with themodel. The results show that the stable time for the velocity and attitude of parachute-payload system of Mars Pathfinder is longer than that on Earth，the altitude loss is more than that on Earth, the symmetry axis of the probe takes longer time to become vertical, and the amplitude of swing angle is larger. These should be specially noted when designing parachute-opening time and timing of work of Marsprobe. The conclusion could provide technology reference for parachute system design of Mars probe. Related Articles | Metrics

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An elevation reconstruction method of multi-channel InSAR based on optimal estimation of common remainder#br# WANG Siyu, CHEN Lifu, YUAN Zhihui, XING Xuemin, MAO Yongfei, WU Hong 2018, 38 (2):  71-76.  doi: 10.16708/j.cnki.1000-758X.2018.0008 Abstract ( 122 )   PDF (6519KB) ( 63 )   Save To improve computational efficiency of multichannel InSAR elevation reconstruction, a rapid elevation reconstruction method based on the optimal estimation of remainder was proposed. Firstly, after the removal of the flat-earth effect, the wrapped interferometric phase of each pixel was drawn and congruence equations of interferometric phase fuzzy number were constructed. Secondly, the optimal estimation method was used to solve the optimal estimation of the common remainder with noise, and the elevation of each target was solved. Finally, the improved method was used to get higher precision reconstruction results. Experimental results show that the algorithm significantly improves the computational efficiencyof multichannel InSAR elevationre construction. Related Articles | Metrics

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Comparison and research on performance of regenerator under oscillating flow CHEN Pengfan, ZHU Jianbing, YE Wenlian, YANG Lie 2018, 38 (2):  77-83.  doi: 10.16708/j.cnki.1000-758X.2018.0004 Abstract ( 268 )   PDF (5935KB) ( 171 )   Save Regenerator is one of the crucial components of Stirling engine. A unit cell model of Ni foam was developed based on the sphere-centered open-cell tetrakaidecahedron which was put forward by Mo Bai. Using this model, the correlation of poredensity, pore diameter and porosity was quantitatively derived. The flow of working gas in stainless steel wire mes (porosity: 0.62~0.83) regenerator and Ni foam (porosity: 0.94~0.98) regenerator was numerically simulated respectively based on the 2-D computational domain of regenerator. The analytical comparison of the above two filler' heat transfer coefficient, pressure drop, and resistance coefficient was conducted. It is shown that the amplitude of pressure drop between inlet and outlet of Ni foam regenerator is 1/400 of stainless steel wire mesh regenerato′s, while the heat transfer coefficient is only 1/5. At last, the parameter Nu/C1/3f was put forward to evaluate the fille′s comprehensive performance. The comparison results show that the Ni foam has the better comprehensive performance than the stainless steel wire mesh, so it has the potential of being used as there generator′s filler of Stirling engine. Related Articles | Metrics