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25 April 2004, Volume 24 Issue 02 Previous Issue    Next Issue

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Optimal Placement of Piezoelectric Sensors/Actuators in Vibration Control of a Flexible Beam Zhou Lianwen Zhou Jun (Northwestern Polytechnical University, Xi'an 710072) 2004, 24 (02):  .  Abstract ( 1503 )   Save A method of finding the optimal locations of piezoelectric sensors and actuators for the control a of flexible structure is presented. The basic equations of the flexible structure bonded with piezoelectric sensors/actuators are derived. The method is based on the orthogonal projection of structural modes into the intersection subspace of the controllable and observable subspaces corresponding to the actuators/sensors. The controllability and observability grammians are then used to weight the projections to reflect the degrees of controllability and observability. This method produces the optimal locations of actuators/sensors. The simulation results show that the vibration of a flexible structure can be suppressed efficiently by using optimized actuators/sensors. Related Articles | Metrics

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Optimal Aeroassisted Orbital Interception and Rendezvous Wu Delong Peng Weibin (Beijing Institute of Astronautical Systems Engineering, Beijing 100076) 2004, 24 (02):  .  Abstract ( 1559 )   Save Optimal trajectories are obtained by using a direct adjoining approach (so called the D form Lagrangian)for the interception or the rendezvous of a target in low circular Earth orbit by a vehicle which is initially in a high orbit. The interception condition is that the attack vehicle has the same position as the target at final time, but the rendezvous condition is that both vehicles have same position and same velocity vector at final time. In this paper, a minimum linear combination of target-escape, or fuel-consumption and flight time as the performance index, and the thrust programming in aeroassisted maneuvers are considered, which will lead to a singular thrust arc over the heating rate boundary in optimal control problem for the special case in which the thrust is singular while the aerodynamic controls are regular. These results show that the complexities introduced by the synergetic maneuver with thrust programming and the necessity to find the solutions in the optimal aeroassisted orbit interception and rendezvous should be carefully treated. Related Articles | Metrics

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A Method of Real-time Orbit Determination Using Self-Calibration Kalman Filter with Restrictions Gao Yaowen Qian Weiping Liu Lisheng Guo Junhai (Beijing Institute of Tracking and Telecommunication Technology, Beijing 100094) 2004, 24 (02):  .  Abstract ( 1665 )   Save In view of the disadvantages in the traditional orbit determination method,such as complicated orbit elements solving, low real time filtering accuracy, uncertain systematic errors and so on, this paper presents and explicates a method of real time orbit determination using self- calibration kalman filter with restrictions. The characteristics of the method are little complicacy, good real time distinction and small computational cost. Simulation results indicate that quick converging and high orbit determination accuracy are also the advantages of the method. There is much prospect of the method being put in practice. Related Articles | Metrics

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Research on Design of Circuit Reliability in FPGA with Defect Clustering Du Wenzhi Tan Weichi (Beijing Institute of Spacecraft System Engineering, Beijing 100086) 2004, 24 (02):  .  Abstract ( 1538 )   Save Mechanism of defects clustering in IC and its influence on manufacturing yield of IC are analyzed in this paper. The influence of defects clustering in FPGA on the reliability of inside fault-tolerance circuit with redundancy is also discussed by using prediction model of manufacturing yield of IC. Hereby strategies of improving its reliability are presented, model for analyzing its reliability is set up and some guidance principles about how to lay are provided. Related Articles | Metrics

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Research on Method of GPS Cycle-slip Detection and Ambiguity Determination Aided by INS Zhao Wei Wan Dejun (Southeast University, Nanjing 210096) Liu Jianye (Nanjing University of Aeronautics and Astronautics, Nanjing 210016) 2004, 24 (02):  .  Abstract ( 1963 )   Save In INS/GPS integrated navigation system, there are two key processes when using carrier phase of GPS. A simple algorithm to determine ambiguity and to detect cycle slip assisted by using INS is brought up in this paper. Mathematics model is deduced and computer simulation is carried out to check the validity of arithmetic. The result shows that cycle slip less than one wavelength can be detected and ambiguity can de determined instantaneously on certain condition. Related Articles | Metrics

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Analysis of Area Navigation Performance of Walker Constellation Deng Zhongmin Xiao Yelun (Beijing University of Aeronautics and Astronautics, Beijing 100083) 2004, 24 (02):  .  Abstract ( 1634 )   Save This paper analyzes the influence of orbit parameters of Walker constellation on area navigation performances by using numerical simulation. The results show that relative phase index of constellation orbit and orbit inclination exert important influence on the quality area navigation performance of constellation. The navigation quality index is more significant to represent the navigation performance of constellation than the GDOP value. Related Articles | Metrics

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The Second Law of Thermodynamic Analysis of the Pulse Tube Cryocooler for Space Application Hou Yukui * Ju Yonglin ** Ma Jun * Zhou Yuan ** (*Chinese Academy of Space Technology, Beijing 100081) (**Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100080) 2004, 24 (02):  .  Abstract ( 1858 )   Save Based on the numerical simulation, the second law of thermodynamics is applied to analyze the irreversible losses in a miniature pulse tube cryocooler (PTC) for space application. Simulation results show that the regenerator is the main part generating irreversible losses in the PTC. The performance of double inlet PTC is better than that of orifice PTC. From the view of the second law of thermodynamics, the reasons of this improvement are as follows. Firstly, the helium gas through the regenerator is reduced, and then the irreversible losses in the regenerator, the connecting tube (between the compressor and regenerator) and the cold heat exchanger are reduced. Thus the power consumed by the compressor is less. In the mean time, the heat transfer between the gas and matrix is performed better, and the net refrigeration power is increased consequently. Simulation results show that Carnot efficiency of the PTC increase from 14% to 16 9% when the cooler change from orifice type to double inlet type. Related Articles | Metrics

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Application Research of Temperature Extrapolation Technology in Thermal Balance Test Fu Shiming Qie Dianfu Liu Feng (Beijing Institute of Spacecraft Environment Engineering, Beijing 100029) 2004, 24 (02):  .  Abstract ( 1614 )   Save In thermal balance test of the spacecraft, using temperature extrapolation technology obtain the ultimate thermal balance temperature of the spacecraft can be predicted accurately and the test duration can be shortened, and the development cost of the spacecraft can be reduced accordingly. The nonlinear least-squares estimation and the extended Kalman filtering (EKF) are two of the most pervasive extrapolation and prediction methods, some important engineering problems about how to apply these two methods in spacecraft thermal balance test are discussed. Related Articles | Metrics

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The Conservative Reliability Growth Model for Complex System with Small Samples Feng Jing Liu Qi Zhou Jinglun (National University of Defense Technology, Changsha 410073) Dong Chao (Electronic Engineering College, Hefei 230037) 2004, 24 (02):  .  Abstract ( 1509 )   Save The Weibull distribution with two parameters is widely used in Aeronautical and Astronauticd products. For complex system with small samples, the shape parameter of Weibull is neither given by a few disable data nor estimated by impersonal method. At present, slove the problem by experts enacting or non-parameter statistic, which is subject to considerable uncertainty. This paper proposed an object and conservative method to estimate the shape parameter, at the same time get the reliability growth model for the system which is developed grading. At last, an example is given to illustrate the usage of the proposed method in engineering application. Related Articles | Metrics

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Reliability Test Study of Eccentric Pump in the Active Fluid Cooled Loop System of Manned Spacecraft Jiang Jun Zhang Ningli Xu Jiwan (Beijing Institute of Spacecraft System Engineering, Beijing 100086) 2004, 24 (02):  .  Abstract ( 1523 )   Save The reliability testing method of space pump package is discussed according to its operating status in space. The test including the test system bench and test results is also described. The test proves that reliability index of the pump exceeds 0 999. Related Articles | Metrics

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Error Analysis of Estimating the Boost Phase of a Trajectory Measured by a Single Satellite Li Yingliang Yi Dongyun Wu Yi (National University of Defense Technology,Changsha 410073) 2004, 24 (02):  .  Abstract ( 2039 )   Save This paper studies the error analysis problem of estimating the parameters of the boost phase of a trajectory under the condition of priori information. A single satellite is applied and the trajectory is measured by the reaching angle of the satellite carried infrared sensor. Through theoretical analysis and combined with Monte Carlo simulation, systematically analyze the influence of three main error source on the trajectory estimation. Some corresponding transaction strategies are also presented. Related Articles | Metrics