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    25 October 2007, Volume 27 Issue 05 Previous Issue    Next Issue
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    Integrated Optimal Design of Piezoelectric Intelligent Structures and Feedback Control
    Wang Xinmin(Beijing Institute of Control Engineering,Beijing 100080)Li Yong(China Academy of Space Technology,Beijing 100094)
    2007, 27 (05):  1-7. 
    Abstract ( 1720 )   Save
    A new approach to the integrated optimal design and the performance criterion of optimal placement based on realistic objective function and constraints was presented.According to the intelligent materials' performance on vibration suppression of flexible structures,the location and sizing of collocated piezoelectric sensor/actuator,including the effect of changes in the mass and the stiffness of the structure by addition of sensor/actuator pairs,and the feedback gains were considered and combined with the quadratic performance criterion used in optimal control to obtain the realistic state-space model of the structure and a composite objective function.By using Lyapunov stability theorem,it was shown that the closed-loop system of flexible structures was global asymptotically stable.In addition,the proposed minimizing performance criterion can be viewed as the trace of the correlative matrix which leads to solutions that are independent of initial conditions of the controlled flexible structure.To solve the optimization problem,the genetic algorithm was utilized.Simulation results not only show that the piezoelectric intelligent structure designed by the proposed approach can fleetly suppress the vibration of the structure,but also demonstrate the validity and feasibility of the proposed approach.
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    Fault Isolation Method of the Attitude Sensors in the Satellite Attitude Control System
    Jiang Gengfeng Xing Yan Wang Nanhua(Beijing Institute of Control Engineering,Beijing 100080)
    2007, 27 (05):  8-13. 
    Abstract ( 2033 )   Save
    Optical sensors and inertial sensors are two kinds of important attitude measuring components.How to isolate the faults of these two kinds of sensors is a difficult problem in the fault diagnosis of the closed-loop attitude control system of satellite.There is analytical redundance between the outputs of these two kinds of sensors deduced from the kinematical equation,so a virtual system can be established.Two different observers can be used for this system,one of which is the Kalman filter used for detecting the fault of both sensors,the other is the isolating observer detecting the fault of optical sensors.Fault isolation can then be achieved by comparing the residuals of these two observers.The proposed method is applied to the satellite control system with sun sensors,infrared earth sensors and gyroscopes,and the mathematical simulation results validated the efficiency of the method.
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    Thermal Chamber Design for Loop Heat Pipe Ground Experiment
    Qu Yan1 Cheng Lin1 Stefano Zinna2 Luan Tao1 Marco Marengo2(1 Institute of Thermal Science and Technology,Shandong University,Jinan 250061)(2 LSRM-Microfluidics Lab,Engineering Faculty,University of Bergamo,Dalmine 24044)
    2007, 27 (05):  14-20+56. 
    Abstract ( 1911 )   Save
    A thermal analysis of loop heat pipe(LHP) ground experiment chamber was carried out by building a physical model under the conditions of natural heat convection and heat radiation.The computation purpose is to achieve the thermal boundary conditions of the LHP space orbital positions in the ground to further secure LHP ground experiment in the coldest and the hottest cases.The general thermal design was made by determining the thermal chamber temperature,insulation,and refrigerant system.Analysis results show that inner chamber wall temperature should vary in the range of-62.1℃ to-10.9℃ in order to realize the LHP space thermal conditions on ground experiment.
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    Design and Simulation of Medium Scale Space Environment Simulator Vacuum System
    Wang Juan Zhuang Damin Wang Jun(Beijing University of Aeronauics and Astronautics,Beijing 100083)
    2007, 27 (05):  21-26. 
    Abstract ( 2320 )   Save
    The design and simulation of the medium scale space environment simulator for the extravehicular activity space suit experiment were discussed.By simulating the temperature of the cryopanel and the relation between the pressure and pumping gas speed of the cryopump,it was verified the vacuum system design was rational.The pre-cooling of the medium scale space environment simulator adopted the open liquid nitrogen system in order to simplify system structure.The structure analysis and the radiation heat load computation were carried out from the cryopanel to the radiation baffle.The effects of the condensing layer of the cryopanel on the cryopump capabilities were analyzed.By simulating cryopanel temperature field and analyzing the maximum of temperature,the cryopanel design was optimized and the capabilities were verified.The oxygen wastage of the astronaut was analyzed to estimate the metabolism producing heat of the astronaut.The medium scale space environment simulator heat loads and the liquid helium demand of the cryopump were obtained.The system design and simulation of the medium scale space environment simulator provides the reference for the research of domestic astronaut extravehicular activity and correlative devices.
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    Legendre Pseudospectral Method for Rapid Lunar Soft-Landing Trajectory Optimization
    Wang Mingguang Pei Tingguo(The Academy of China Aerospace Times Electronic Corporation,Beijing 100070)Yuan Jianping(College of Astronautics,Northwestern Polytechnical University,Xi'an 710072)
    2007, 27 (05):  27-32. 
    Abstract ( 1840 )   Save
    Determining the best soft-landing trajectory of the lunar probe from the lunar satellite orbit involves the solution of an optimal control problem.This problem,which was considered to be difficult,was traditionally solved on the ground prior to flight.First,a new hypothesis was introduced according to the distinguished features of the lunar and soft-landing trajectory.Then,a set of dynamics and kinematics equations of motion was simplified,and this simplification reduced the computation load greatly.Next,the optimal control problem of soft-landing trajectory was transformed into a constrained parameter problem by using Legendre pseudospectral method,and nonlinearprogramming method(methods of multipliers and BFGS) was applied to solve the transformed problem.The simulation results show that the algorithm can generate a feasible soft-landing trajectory of about 300 seconds flight time in 30 seconds on the desktop computer.
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    Application Study of the Normal Atmosphere Pressure Thermal Test Technique in the Development of the System-level Spacecraft
    Tang Bochang Zhang Jiaxun(China Academy of Spacecraft Technology,Beijing 100094)
    2007, 27 (05):  33-37+64. 
    Abstract ( 1804 )   Save
    The design of the cabin used in the test,the scheme methods of this technique were disscussed.Then the test results and several important issues associated with the test process were analyzed.The test goal,which was to check the satellite's realiability,was fulfilled.This technique is of great importance to manufacturing process rebuilding of spacecraft development.
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    Scheme of Fluid Loop System on Manned Spacecraft for Transport
    Fan Hanlin Huang Jiarong Liu Qingzhi Zhang Li(China Academy of Space Technology,Beijing 100094)
    2007, 27 (05):  38-43. 
    Abstract ( 1730 )   Save
    The fluid loop is the most important part of the thermal control system on manned spacecraft.The fluid loop must meet the thermal requirement of all kinds of the conditions that may be occur during the whole period,working with other passive thermal control measure on spacecraft.At the same time,it should occupy the resource of the spacecraft as less as possible.The scheme and configuration of the fluid loop were determined basing on analysis and comparison.Considering the thermal design of target spacecraft to be docked with,the emphasis of the design was put on solving the thermal problems during the period of two spacecrafts combined together.The main requirements and emphases of designing fluid loop were presented.Based on the analysis of energy balance,two kinds of scheme were designed.And the performance of two schemes was compared.Finally,some suggestions on choosing working fluid of fluid loop system.
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    Improved Evaluation Method of Service Availability for Satellite Constellation
    Xu Jia(China Academy of Space Technology,Beijing 100094) Han Chao(Beijing University of Aeronautics and Astronautics,Beijing 100083)
    2007, 27 (05):  44-49. 
    Abstract ( 2169 )   Save
    A weighted statistical evaluation model and corresponding simulation flow for evaluating the figure of merit of constellation service availability were suggested by dividing the satellite constellation into two groups according to whether the satellites in the orbital planes having fault satellite and by using probability and combination method.Using this model and simulation flow,an univariate study on the effects of variation of constellation configuration and orbital parameters on its service availabilities(SA) was performed.The results indicated that the number of orbit plane,relative phase factor and orbital height of the constellation have effect on its service availabilities.The proposed model has explicit physical meaning and can greatly reduces the evaluation time of SA merits.And the conclusions can help to select the optimal constellation configuration and orbital parameters in conceptual design phase.
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    Weighted Geometric Dilution of Precision's Analysis for Mixed Constellation Navigation System
    Wang Mengli Sun Guangfu Wang Feixue Yong Shaowei(School of Electronic Science and Engineering,National University of Defense Technology,Changsha 410073)
    2007, 27 (05):  50-56. 
    Abstract ( 1937 )   Save
    In mixed constellation navigation system composed of different satellites or compatible systems,considering range errors caused by the ephemeris errors were different,weighted geometric dilution of precision was used in constellation selection,position accuracy evaluation and integrity monitoring instead of geometric dilution of precision.By calculating the different satellite combinations in constellation of geostationary earth orbit and middle earth orbit,it was found that weighted geometric dilution of precision was more valid in constellation selection and position accuracy evaluation in mixed constellation navigation system with different range errors.In such occassions that exigent requirements with position accuracy,high reliability of integrity monitoring etc,weighted geometric dilution of precision is reliable than geometric dilution of precision.
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    Fast Transfer Maneuvers between Holding Points in the Closing Phase of Spacecraft Rendezvous
    Zhu Renzhang Hu Xiting(Beijing University of Aeronautics and Astronautics,Beijing 100083)
    2007, 27 (05):  57-64. 
    Abstract ( 1713 )   Save
    Fast transfer strategies between V-bar holding points for the closing phase of spacecraft rendezvous were investigated in terms of C-W solutions.Bidirectional thrusters have to be used to execute transfer between V-bar holding points within half of the orbital period.For this reason,five bidirectional-thrust maneuvers were presented: 1) bidirectional impulses at the beginning and end points,2) bidirectional continuous thrusts during the transfer,3) bidirectional impulses at the beginning point and bidirectional continuous thrusts during the transfer,4) bidirectional continuous thrusts during the transfer and bidirectional impulses at the end-point,5) tangential impulses at the beginning and end points and radial continuous thrust during the transfer(straight line transfer).All the five maneuvers have good safety.Their free-flight trajectories can not enter into the safety area centered at the mass center of the target vehicle in case that any maneuver thruster has failure.The bidirectional-impulse maneuver has the lowest velocity increment and the maximum visual angle.The straight line transfer has the visual angle equal to zero,but it consumes more propulsion when the transfer time T>0.292P(P is the orbital period).Thus,it's better to choose the bidirectional-impulse maneuver,if the visual angle can meet system design requirements.When the transfer time T<0.292P,the straight line transfer can be considered as an alternative.
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    Seven-hole Probe Measurement on Parachute Flow Field
    Yu Li1 Teng Haishan2 Ming Xiao1(1 College of Aerospace Engineering,Nanjing University of Aeronautics and Astronautics,Nanjing 210016) (2 Beijing Institute of Space Machine & Electricity,Beijing 100076)
    2007, 27 (05):  65-71. 
    Abstract ( 1888 )   Save
    The flow field of parachute was quite complex because the canopy was a kind of soft fabrics with porosity.It was very difficult to measure the flow field around the canopy with ordinary methods.In wind tannel,seven-hole probe was adopted to measure the flow field around the parachute with a flat,circle canopy without vent.Using the mixed programming technology of Labview combined Matlab engine could easily realize the data collecting and processing.The velocity and pressure distribution were achieved.The flow field topological structures of parachute flow fields and the differential pressure distribution along radial were obtained.This research solved the difficult problem of quantitative measurement on parachute flow field.It is a good technical option to analyze the aerodynamic characteristics of the flow field around the parachute.
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