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25 December 2019, Volume 39 Issue 6 Previous Issue   
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Research on unconventional dynamic problems for #br# small satellites
BAI Zhaoguang, YANG Xinfeng, CUI Yufu, LIU Zhijia, DENG Weihua
2019, 39 (6):  1.  doi: 10.16708/j.cnki.1000-758X.2019.0044
Abstract ( 34 )   PDF (2387KB) ( 11 )  
Some special dynamic problems encountered in small satellites were studied, and the corresponding solutions were developed. To solve the difficulties of analysis and test for high level shock much higher than the frequentlyused shock test standard spectrum, a method was proposed to analyze the high level shock. As for problems in strength design under random vibration for small satellites, the influence of the modal effective mass ratios and modal frequencies on quasistatic load computation was studied. The analysis shows that neglecting the coupling of modal effective masses and the coupling of modal frequencies leads to large error in quasistatic load computation under random vibration. The method for quasistatic load computation with consideration of the coupling of modal effective masses was proposed. Finally, the study on vibration reduction was carried out for a small satellite, and the vibration reduction for sine vibration and random vibration was analyzed. The calculation method of the main frequency for vibration reduction system with symmetrical installation was given.
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Optimal caging configuration design for flat noncooperative target capture based on multifingered mechanism
SUN Chong, WAN Wenya, CUI Yao, YUAN Jianping
2019, 39 (6):  8.  doi: 10.16708/j.cnki.1000-758X.2019.0045
Abstract ( 15 )   PDF (10599KB) ( 8 )  
Aiming at the problem of space noncooperative target capture, a method was proposed for the optimal cagingbased capture configuration design of multifinger for flat noncooperative objects. The core of the method is: selecting the lead finger of the capture mechanism and controlling it to track the caging point; calculating the feasible configuration of the follow fingers according to the geometric relationship of the capture mechanism; utilizing the cagingbased capture constraints, as well as collision detection constraints, and selecting the effective cagingbased capture configuration. Compared with the existing methods, the method adopts the simple mode of leaderfollowers, which can greatly reduce the calculation of the capture configuration optimization, and is suitable for realtime onorbit capture of space noncooperative targets. Further, the concept of safe capture margin is introduced to quantify the margin between the capture mechanism and the space noncooperative target. Considering the collision avoidance between the noncooperative target and the capture mechanism before the formation of the capture configuration, the configuration with maximum safe capture margin is chosen as the optimal. In order to verify the effectiveness of the proposed method, it is applied to the quadrilateral and regular pentagon moving target capture problems respectively. The simulation results show the effectiveness of the proposed algorithm.
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Attitude and orbit coupling control for flyaround observation of multisatellite proximity operation
XU Ying, ZHANG Jin, YU Moyao, XU Dandan
2019, 39 (6):  21.  doi: 10.16708/j.cnki.1000-758X.2019.0046
Abstract ( 129 )   PDF (6611KB) ( 54 )  
Aiming at the observation mission of multisatellite proximity operation, dynamics models of relative attitude and orbit are established. Two kinds of desired triangular formation configurations of observation satellites in elliptical and space circular orbits are considered respectively. The desired attitude is designed that the observation satellite's line of sight always points to the target satellite. The proportionaldifferential control law based on the quaternion and angular velocity error feedback and an improved guidance method based on artificial potential field method are used to control the relative attitude and orbit. The simulation results show that all observation satellites can effectively track the desired relative attitude and desired relative orbit under the action of the control law. In the triangular formation configuration of space circular orbit, after starting from the same initial position, the formation configuration of three observation satellites always keeps a regular triangle. Moreover, the side length of the regular triangle increases gradually from zero to finally the desired value.
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A modified Klobucharlike model of ionosphere delay with consideration for seasons for 45°(N) latitude belt
LI Qihang, WANG Jian, LIU Ruihua
2019, 39 (6):  30.  doi: 10.16708/j.cnki.1000-758X.2019.0047
Abstract ( 24 )   PDF (6872KB) ( 4 )  
Ionospheric delay is one of the most serious error sources in GNSS (Global Navigation Satellite System). For singlefrequency GNSS aircraft users, it is essential to apply an effective and simple broadcast ionospheric model to mitigate the ionospheric delay. The classical Klobuchar ionospheric model has a relative error of 50%~60%. In 45°(N) belt, a higher accuracy of correcting is needed. Considering the significant impact of season on the ionosphere in middle and high latitudes, GIMs (Global Ionospheric Maps) were analyzed for the variation of nighttime TEC (Total Electron Content) valleys with seasons and the variation of daytime TEC peaks with seasons. By improving the amplitudes of the cosine term and nighttime term in the classical model without adding extra coefficient, a Klobucharlike ionospheric model suitable for flightcongested latitudes was proposed. With GIM as a reference, the ionospheric relative errors of the new model for nighttime and for daytime reach 82% and 80% respectively,suggesting the new model has the better accuracy in depicting the ionospheric delay of the area.
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Autonomous navigation based on Deimos lightofsight for Mars approaching phase
TANG Qingyuan, WANG Xiaolei
2019, 39 (6):  38.  doi: 10.16708/j.cnki.1000-758X.2019.0048
Abstract ( 23 )   PDF (3716KB) ( 6 )  
The accuracy of navigation during Mars approaching phase is limited by large time delay, discontinuity of radio signal, and insufficient measurement information. An autonomous navigation method is proposed based on a succession of Deimos lightofsight (LOS) measurements relative to the spacecraft. Each position and velocity estimation is achieved through a group of Deimos LOS measurements. This method is independent of prior information such as direction of orbit asymptote. In consideration of the case that Deimos and Mars would be in the same field of view, the orbit radius can be achieved by combining Mars LOS measurement and Deimos ephemeris, which can act as supplementary measurement to improve navigation accuracy. The orbit estimation accuracy and feasibility of this navigation scheme are verified through numerical simulation, which shows that the method can meet the requirement of approaching phase orbit determination during future Mars exploration.
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Control method of fast launching and positioning for geostationary satellites#br#
CHEN Jizheng, SUN Songtao, FENG Gang, XIAO Yuzhi
2019, 39 (6):  47.  doi: 10.16708/j.cnki.1000-758X.2019.0049
Abstract ( 22 )   PDF (6501KB) ( 10 )  
A method of fast launching and positioning for GEO satellites is proposed. After the satellite is launched into the GTO orbit, it is maneuvered into any designated position in the GEO orbit by the upper stage or by itself within 48 hours. Considering the constraints of time and TeleTracking & Controlling, the nominal trajectory of fast positioning is optimized for minimizing fuel consumption. Based on the nonsingular Equinoctial orbital elements, an explicit guidance is proposed for spacecraft maneuvering and positioning with finite thrust. The simulation shows that the fast launching and positioning control of GEO satellite can be achieved by using the proposed maneuvering strategy, trajectory optimization method and guidance law.
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Design of LEO satellites augmented constellation for navigation
TIAN Ye, ZHANG Lixin, BIAN Lang
2019, 39 (6):  55.  doi: 10.16708/j.cnki.1000-758X.2019.0050
Abstract ( 24 )   PDF (7032KB) ( 15 )  
A constellation design method of LEO (Low Earth Orbit) satellites augmentedconstellation for navigation is presented since global LEO satellites becoming a hot spot. Firstly, the relationship between the orbit altitude and the visible spherical crown is deduced, thus the constellation altitude can be computed with the space debris distribution, economy and collision risk. Then, the relationship between the elevation and the orbit inclination is derived, and meanwhile the constellation inclination is determined to get north and south poles coverage. Next, compared with Iridium, it is demonstrated that a single constellation can′t achieve a uniform visible satellites distribution and DOP(Dilution of Precision)on global scale. Finally, an LEO satellites constellation design method is proposed, which can achieve global coverage while make the DOP (Dilution of Precision) and the visible satellites distribute evenly around the world. The results show that the mixed constellation designed by the method can achieve a global coverage and even distribution of visible satellite numbers and DOP.
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Physical experiment and discrete analysis of impact between conical object and simulated lunar soil
LIANG Shaomin, WANG Yongbin, WANG Liwu, WU Shiqing, LIU Huan, JI Shunying
2019, 39 (6):  62.  doi: 10.16708/j.cnki.1000-758X.2019.0051
Abstract ( 15 )   PDF (7535KB) ( 9 )  
During the lunar probe landing, the lander cushion firstly comes into contact with lunar soil. Therefore, the dynamic characteristics of the cushion are directly related to the safe landing of the detection equipment and the implementation of the subsequent operation. Considering the advantages and disadvantages of cushion shape for the study of landing process, a conical object to replace the actual cushion was chosen. The methods of experiment and discrete element numerical simulation were used. The effects of conical angle and impact energy of conical object during the impact process were studied by simulating the impact of conical object on lunar soil. The results obtained by discrete element simulation are consistent with the experiment. The results show that the impact energy is a major factor in the impact process. When conical objects with different conical angles are used, the impact depth and impact duration decrease with the increase of the conical angle, while the impact force peak gradually increase. In addition, the velocity vector of granular in the impact process was discussed, and the physical properties of granular medium under impact load were discussed from a microscopic perspective. Reference and factual basis are provided for the design of space lander. The above results also have certain reference value for the penetration detection of the lunar surface by special equipment.
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Attitude anomaly detection method for spatial target RCS sequence
HU Mengxiao, LAI Jiazhe, XU Can
2019, 39 (6):  72.  doi: 10.16708/j.cnki.1000-758X.2019.0052
Abstract ( 11 )   PDF (3576KB) ( 7 )  
Accurate and fast judgment of the abnormality of the space target attitude motion mode is of great significance for the monitoring of space targets. Aiming at the spatial target radar cross section (RCS) sequence, an unsupervised machine learning anomaly detection method based on wavelet packet decomposition (WPD) energy spectrum characteristics was proposed, and the oneclass support vector machine (OCSVM) was adopted to verify the anomaly detection effect. Several typical anomaly scenes were set up for simulation analysis. The experimental results show that the method can effectively detect the abnormal attitude of the threeaxis stable space object with unstable rotation. Compared with traditional statistical parameter features, wavelet transform statistical parameter features and energy feature of attitude discrimination method, it has the characteristics of high detection probability and good robustness.
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Aerodynamic and structural simulation of space reentry inflatable aeroshell at high angle of attack
ZHANG Zhang, WU Jie, WANG Liwu, HOU Anping, CAO Xu, WANG Qi
2019, 39 (6):  80.  doi: 10.16708/j.cnki.1000-758X.2019.0053
Abstract ( 13 )   PDF (5588KB) ( 6 )  
For the description of the aerodynamic and structural characteristics of the space reentry inflatable aeroshell at high angle of attack, the CFD model was used to calculate the flow field distribution and aerodynamic coefficients at different angles of attack. At the same time, the finite element model considering the internal pressure was established. Using the hypersonic flow field as the input, the influence of aerodynamic force on the static characteristics of structure at different angles of attack was analyzed by the one way fluidstructure interaction method. The results show that with the increase of angle of attack, the axial force coefficient decreases as a whole, while the normal force coefficient and pitching moment coefficient show Mtype and Wtype trends. Furthermore, the maximum stress of the structure increases with angles of attack increment, and the maximum increase is near 45° angle of attack.
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High speed onboard router based on LEO constellation
LYU Yuancao, WANG Fengchun, XU Nan, HAN Xiaodong, FENG Yanjun, XING Chuan
2019, 39 (6):  87.  doi: 10.16708/j.cnki.1000-758X.2019.0054
Abstract ( 26 )   PDF (5344KB) ( 33 )  
With the explosion of the internet traffic, the IPbased large volume data transmission provided by satellite network becomes a prerequisite to integrate satellite network and terrestrial network. Onboard router,whose transmission rate and QoS (Quality of Service) determine the throughput and efficiency of the entire network,is the key facility of the satellite network. Based on the low throughput of existing onboard routers, a design of high speed onboard router for LEO (Low Earth Orbit) satellite constellation is proposed. Implementing dynamic routing into the snapshotbased routing scheme makes it possible to minimize packet drop when link failure happens. This scheme enables iterative data switching after one time route computing. By using sharedmemory mode to build switchingmemory unit, also with Spacewire and Serdes interface units deployment, the intersatellite throughput can achieve up to 51 Gbit/s in theory. Moreover, the onboard router supports IPbased transmission, which lays the foundation for integrating with terrestrial network.
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