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25 June 2000, Volume 20 Issue 03 Previous Issue    Next Issue

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Research of a New Type of Magnetometer Application in Measuring Performance of Facilities on Satellite Ni Yibin (Beijing Institute of Spacecraft System Engineering,Beijing 100086) Chen Dexiang (Beijing Institute of Control Engineering,Beijing 100080) Jia Wenkui (Center for Space Science and Applied Research,Beijing 100080) 2000, 20 (03):  .  Abstract ( 1635 )   Save A novel type of magnetometer is introduced.The zero magnetostrictive amorphous material ribbon is used as the probe's core,and multivibrator resonance oscillator in the circuit design is adopted.The magnetometer has good performances such as simple structure,convenience operation and high response frequency.The response frequency is up to 5 kHz.The operation principle of magnetometer is explained and its applications in measuring some facilities on satellite are studied. Subject Term Magnetometer Amorphous compound Multivibrator Research] , in which HCR, HVR and HPR is the ratio of current, voltage and power of the Holographic Ratio Network respectively. Based on this relation an ideal attenuator can be designed according to the following equation: A=20 Log(HCR)=20 Log(HVR)=10 Log(HPR). Experiments on models are full proof the theory of Holographic Ratio Network is valid. , in which HCR, HVR and HPR is the ratio of current, voltage and power of the Holographic Ratio Network respectively. Based on this relation an ideal attenuator can be designed according to the following equation: A=20 Log(HCR)=20 Log(HVR)=10 Log(HPR). Experiments on models are full proof the theory of Holographic Ratio Network is valid. Related Articles | Metrics

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A Study on the Equivalent Model of Second Reflect Mirror Unit of a Remote Sensing Camera Wang Jun Wang Jiaqi Lu E (Changchun Institute of Optics and Fine Mechanics,Changchun 130022) Wang Xin (Jilin University of Technology,Changchun 130025) 2000, 20 (03):  .  Abstract ( 1529 )   Save Modal test analysis is widely used in the structural mechanism studies in the aerospace field and plays a very important role.A method to carry out modal test for vulnerable or precious structure is studied in this paper.This method is named equivalent model method.Modal test can be simplified with the development of the equivalent model.In order to make the equivalent model is equivalent to its prototype,it is necessary to keep the geometrical and stiffness equivalent.The geometrical equivalent is satisfied through the UNIGRAPHIC software at first,the mass of the test model is equal to the prototype.Based on the basic plate theory and structural sensitivity analysis,this paper discussed the theory of equivalent model whose structural material is different from the prototype.This can make sure that the stiffness of test model is equivalent to its prototype.In order to verify this theory,it is applied to the second reflect mirror unit of a remote sensing camera.Through analysis,any frequency and modal shape of the test model of the second reflect mirror unit is equal to its prototype.So if this method is used in the similar condition,satisfactory result can be obtained.This method can be used as a solution to simplify the modal test of aerospace equipment. Related Articles | Metrics

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Dynamic Model of a Rigid-flexible Coupling Nonlinear System Chen Yushu Yang Caixia (Tianjin University,Tianjin 300072) 2000, 20 (03):  .  Abstract ( 1620 )   Save The dynamic equation of a rigid-flexible coupling nonlinear system is derived based on Lagrange Equation.The effect of satellite's relative three-dimensional motion on orbit coordinate,flexible vibration of antenna's surpporting beam caused by satellite motions,the nonlinear angle displacement resulted from the flexible of GDA and scanning motions of the antenna are considered.This dynamic equation shows the coupling motion and dynamic behaviors more completely.Thus some simplified dynamic equations on different conditions are derived.So,when the original system's vibration is analysed,just the corresponding result is obtained.The method is also suitable for analysing dynamic behaviors of the general. Related Articles | Metrics

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The Non-parameter Method of Recognising Two-types Space Targets Quan Bei Dai Zhengjian Hu Weidong Yu Wenxian (National University of Defence Technology,Changsha 410073) 2000, 20 (03):  .  Abstract ( 1529 )   Save Based on the narrow band radar characterization of space targets,a method of non parameter statistics,named the theory of runs,is adopted to identify the stable manner of space targets and to classify them into rotating round its centroid and non rotating . Related Articles | Metrics

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Fractal Analysis of Tracking Residual Data for Vehicle Zhu Jubo (National University of Defense Technology,Changsha 410073) 2000, 20 (03):  .  Abstract ( 1662 )   Save Based on Fractal Brownian Motion (FBM) model,tracking residual data for vehicle is processed.According to the characteristics of the data,a new method to get the scale interval is present,which is more accurate.Simulating and actual results show that the method has high precision and is easily used in practise.Using FBM model and the method the fractal dimensions for many data are estimated.The results show that fractal dimension of data from tracking vehicle by firing liguid is less than that by firing solid. Related Articles | Metrics

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Composite Adaptive Control for Space Manipulators Wang Jing Wang Haoying Liu Liangdong Liang Bin (Beijing Institute of Control Engineering, Beijing 100080)$$$$ 2000, 20 (03):  .  Abstract ( 1635 )   Save For the space manipulator with an attitude-controlled base, the parameters of the adaptive control is generally driven by tracking errors. But except of tracking errors, the prediction errors also include parameter information. The detailed analysis of the dynamic characteristics of the space manipulator with an attitude-controlled base is provided, the prediction model for the system is developed, and a composite adaptive control algorithm in which the parameters is driven by both tracking errors and prediction errors is presented. Results on global asymptotic and quick tracking convergence are established and confirmed by simulation. Related Articles | Metrics

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Analysis of Orbit and Frequency Coordination of Satellite Networks Gao Xiaoyang (China Telecommunications Broadcast Satellite Corp.,Beijing 100083) 2000, 20 (03):  .  Abstract ( 1644 )   Save Basing on ITU Recommendations,the reasonable and achievable calculation methods are given,which can solve such problems as antenna gain,polarization isolation,rain attenuation and the protection criteria for the SCPC carriers.It is also stressed that there are different definitions for the power density when it is used in different situations. Related Articles | Metrics

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A Measurements Smoothing Method Based on Optimal Knots Spline Approximation Guo Junhai (Beijing Institute of Tracking and Telecommunication Technology,Beijing 100094) 2000, 20 (03):  .  Abstract ( 1851 )   Save A smoothing method for noisy measurements based on optimal knots spline is presented.Describes the objective movement using the B spline with free knots,and in terms of the least square principle,the optimal knots distribution is searched employing the nonlinear optimization.Consequently,the approximative process is adaptively fit for the objective movement,and the approximative precision is improved.The ideal smoothing and differentiation smoothing effect can be obtained even if the object moves rapidly. Related Articles | Metrics

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An Algorithm for Separation Time of Manned Spacecraft Emergency Rescue at Low Altitude Zeng Guoqiang Ren Xuan Jia Peiran (College of Astronautic and Material Engineering,National University of Defense Technology,Changsha 410073) 2000, 20 (03):  .  Abstract ( 1706 )   Save An algorithm for separation time T a of manned spacecraft reentry capsule from escape system is discussed.At first,an approximate solution of escape trajectory is deduced.Then,a real-time algorithm for separation time T a is presented,which is based on the approximate solution.Finally this simple algorithm is proved to be useful for increasing the probability of success of emergency rescue by numerical simulation. Related Articles | Metrics

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Kinematic Singularity and its Research Progress in Single Gimbal Control Moment Gyroscope Systems Wu Zhong Wu Hongxin (Beijing Institute of Control Engineering,Beijing 100080) Chou Wusheng (Beijing University of Aeronautics and Astronautics,Beijing 100083)$$$$ 2000, 20 (03):  .  Abstract ( 1582 )   Save The kinematic singularity principle of Single Gimbal Control Moment Gyroscope (SGCMG) systems is introduced and the survey of research progress in kinematic singularity is made.It is concluded that recognization of the singular principle is too simple to meet the need of nonsingular steering in SGCMG systems at present.It is pointed out that distribution and avoidability of singular points in gimbal space will be the main focus in the future. Related Articles | Metrics