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    25 December 2007, Volume 27 Issue 06 Previous Issue    Next Issue
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    X-ray Pulsars Based Autonomous Navigation Scheme for the Deep Space Explorer
    Qiao Li Liu Jianye Xiong Zhi Zheng Guanglou (Navigation Research Center,Nanjing University of Aeronautics and Astronautics,Nanjing 210016)
    2007, 27 (06):  1-6+18. 
    Abstract ( 1755 )   Save
    An X-ray pulsars based autonomous navigation system can provide sufficient navigation information,such as position,velocity,time and attitude.Using the measurements detected from the X-ray pulsars,and incorporating the measurements with the spacecraft dynamics, an approach is developed to determine the estimated solutions of the spacecraft orbit.The principle of this approach was presented.Based on the existing spacecraft navigation system,an X-ray pul- sar-based navigation scheme was provided.The hardware component,the system structure,and the integrated navigation architecture based on multi sensors were described.Finally,according to the simulation data,the precision of this scheme was estimated.
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    Backstepping Design of Attitude Tracking Control Law
    Zhan Yi Zhang Honghua (Beijing Institute of Control Engineering,Beijing 100080)
    2007, 27 (06):  7-11+30. 
    Abstract ( 1927 )   Save
    Backstepping control scheme was an effective way to design control laws of a cascade system.Quaternion-based attitude equations of a rigid body was a typical cascade system.For the rigid-body attitude tracking control problem with influence of constant disturbance torques,the backstepping control method was used to design a quaternion-based tracking control law for a rigid body with integral terms,which were used to reduce steady-state errors caused by constant disturbance torques.Then the global stability of the control law was also achieved by adding of cross terms in Lyapunov candidate function.The control law is validated by simulations.
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    Analysis of Observable Degree in Autonomous Celestial Navigation System of Lunar Orbiter
    Liu Ping Wang Dayi Huang Xiangyu (Beijing Institute of Control Engineering,Beijing 100080)
    2007, 27 (06):  12-18. 
    Abstract ( 2021 )   Save
    An autonomous orbit determination system based on two angles and selenocentric distance was studied.One angle was between the lines of sight to a star and selenocentric direction, and the other was between the sun and selenocentric direction.A modified observability analysis method defined by the spectral function was presented through the study on some nonlinear system. And the relationship between the observable degree and the accuracy of the system was proved.The simulation resalts show that the modified method is feasible.
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    Investigation of Small-scale Flat-plate Type Capillary Pumped Loop for High Heat Flux Applications
    Wan Zhongmin Liu Wei Zhang Liang Ming Tingzhen (College of Energy and Power Engineering,Huazhong University of Science and Technology,Wuhan 430074)
    2007, 27 (06):  19-24. 
    Abstract ( 1856 )   Save
    The operational behavior of small-scale flat-plate type capillary pumped loop (CPL) at high heat fluxes was analyzed.The total pressure loss along the loop and maximum capillary pressure of the evaporator wick for different working fluids were obtained.The analysis results show that ammonia working fluid had better performance and higher capillary limit,and capillary limit was affected significantly by vapor line radius and working fluid density.The working fluid transmission coefficient was introduced as an important criterion for choosing working fluid.The numerical model of porous wick,metal wall and fluid region of CPL evaporator were established, and the entire evaporator is solved with SIMPLE algorithm as a conjugate problem.The numerical results are obtained and the effect of evaporator metal side wall conduction on the working limit of system is discussed.The side wall effect working limit existed in the small-scale flat-plate type CPL evaporator is introduced.The obtained results are useful for the design of small-scale flat-plate type CPL evaporator.
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    Adaptive Attitude Tracking Control of Flexible Satellite
    Zong Hong Zhang Honghua Xu Fuxiang (Beijing Institute of Control Engineering,Beijing 100080)
    2007, 27 (06):  25-30. 
    Abstract ( 1871 )   Save
    For the satellite with rapid orbit or attitude maneuver ability,its inertia changes greatly with the fuel consumed in orbit,and consequently the mass parameters appear to be uncertain.For the flexible satellite with inertial matrix unknown,the attitude tracking control problem was solved.Considering the target angle rate changing,an adaptive attitude tracking control law was designed based on the error quaternion,and the corresponding close system stability was also proved.The numerical simulation results show the effectiveness of the proposed adaptive control strategy for the satellites with inertia unknown.
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    Modal Identification Algorithm Based on Cross-correlation of Impulse Response
    Liu Xinghan Wang Yueyu (China Academy of Space Technology,Beijing 100094)
    2007, 27 (06):  31-36. 
    Abstract ( 1828 )   Save
    The signal-noise-ratio can be greatly improved after corresponding computations of impulse response performed.The cross-correlation related to a reference point was proposed to identify the structural modal parameters.Theoretical analysis and numerical examples indicate that the identification precision is significantly increased under the same noise condition by the use of the improved algorithm based on cross-correlation.
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    Investigation and Analysis for Landing Impact on Buffer Seat System
    Xie Yan Lei Yongjun Li Daokui Zhou Jianping (College of Aerospace and Material Engineering,National University of Defense and Technology,Changsha 410073)
    2007, 27 (06):  37-41. 
    Abstract ( 1895 )   Save
    A dynamic model of the buffer seat was established according to the characteristics of the reentry capsule landing,equivalent land impact acceleration and work mechanism of the bumper.The method was given to calculate dynamic response of arbitrary position on buffer seat. Numerical simulations prove the modeling and calculation are true.The influence of the landing conditions,positions on the seat,and mechanics of buffer on the astronaut's chest-back and head- pelvis acceleration were studied respectively.A good reference to enhance the work performance of the buffer seat was provided.
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    Low Energy Proton Effects on Solar Absorptance of Thermal Control Coatings
    Feng Weiquan~1 Wang Rong~2 Ding Yigang~1 Zeng Yibing~3 Liu Yuming~1 (1 Beijing Institute of Satellite Environment Engineering,Beijing 100029) (2 Institute of Low Energy Nuclear Physics,Beijing Normal University,Beijing 100875) (3 Beijing Institute of Astronautics Material and Craft,Beijing 100076)
    2007, 27 (06):  42-47. 
    Abstract ( 2140 )   Save
    The low energy proton in space radiation environment results in solar absorptance increase of external thermal control coatings since low-energy proton deposits all its energy at surface.The experiments of low proton irradiation test was performed for six types of thermal control coating as S781 organic white paints,SR107-ZK organic white paints,ACR-1 organic white paints,OSR second-surface mirror,F46 second-surface mirror,and Kapton second-surface mirror. The 48keV proton irradiates theses samples for about 360 hours under vacuum condition, accumulated flux to 2×10~(15) p/cm~2.The in-situ measurements for solar absorptance were carried out during irradiation.All six thermal control coatings increase in different extent.The organic white paints are the highest one.Two polymer film second-surface mirrors are the second.The OSR sec- ond-surface mirrors is the best stable in solar absorptance.SEM and XPS analysis shows that the structure of ZnO pigments,polymerized film and bond are degraded during irradiation of low- energy protons,making high reflective pigment and transparent polymer dark and opaque,causing increases of solar absorptance of thermal control coatings.
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    Discussion about the Variance of the Downlink Ranging Modulation Index in Deep Space
    Wu Xueying Sun Zezhou (China Academy of Space Technology,Beijing 100094) Jin Pengjia (Shanghai Aerospace Electronic Co.Ltd,Shanghai 201800)
    2007, 27 (06):  48-53. 
    Abstract ( 1642 )   Save
    The downlink ranging modulation index was variable while the signal to noise ratio (S/N) changes in the uplink channel or the telecommand and ranging operates simultaneously or respectively,which was due to the multi-subcarrier modulation and the structure of the transponder.The expressions were formulated and the computed data and test results were compared.And the test data is in accord with the principle analysis result.In addition,the expressions are different due to the different structure model of transponders.The expressions deduct by the paper,for example,are different form that recommended by CCSDS standards.
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    Analysis and Correction Techniques of Movement Influence on Inter-Satellite Two-way Time Transfer
    Zhong Xingwang Chen Hao (Xi'an Institute of Space Radio Technology,Xi'an 710000)
    2007, 27 (06):  54-58. 
    Abstract ( 1766 )   Save
    The satellite-to-satellite range and time difference measurement were necessary to distributed spacecraft and formation flying systems.The method of inter-satellite two-way time transfer (TWTT) is presented.The measurement data process algorithm for TWTT is deduced and the movement influence on TWTT is analyzed in detail.And then the range and time difference errors are given when satellite movement is ignored.
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    Analysis of the Polarization Vector Obliquity Direction for Satellite Tracking
    Chen Ju (China Xi'an Satellite Control Center,Xi'an 710034)
    2007, 27 (06):  59-63. 
    Abstract ( 2047 )   Save
    While ground station is tracking satellite,antenna polarization vector that was defined at the coordinate of the satellite had shifted,and orientation of polarization vector was different as station geography diverse.The polarization vector offset is correlative with the station geography position and the satellite spotting.In order to realize the polarization vector matched for tracking satellite,we should ensure polarization vector obliquity direction.The vectors of antenna polarization adopting a coordinate transformation methods is analyzed in order to seek out a relative connection about the polarization vector obliquity between the satellite coordinate and the ground station coordinate,and to obtain the data graph of the polarization vector obliquity,which would serve to the ground station tracking satellite.
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    Modeling and Algorithm of Scheduling Earth Observation Missions with Multi-instruments
    Zhu Zhanxia Yang Bo Yuan Jianping (Northwestern Polytechnical University,Xi'an 710072)
    2007, 27 (06):  64-68. 
    Abstract ( 1822 )   Save
    The earth observation missions planning was presented when there were several instruments on board.First,a set of mathematical models of this combined optimal problem were set up,in which we consider the maximum of science and economy benifits and the limitation of resources.And then,this combined optimal problem was studied by using genetic algorithm.Some computer simulations were performed.The results show that the model is valid and the genetic algorithm is better than greedy algorithm.
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