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Li D.-Z.,Institute of Telecommunication Satellite | Yu D.-Y.,China Aerospace Science and Technology Corporation | Ma X.-R.,China Aerospace Science and Technology Corporation
Gongcheng Lixue/Engineering Mechanics | Year: 2011

It is difficult to calculate the sensitivity coefficients of multiple eigenvalues for large complex structures due to lack of usual differentiability with respect to a design variable, and the equilibrium equation constraints if exists in the model will lead to nonconvex programming. Consequently the global optimum is difficult to find. To avoid this intractable issue, this paper presents a new optimization model for truss structures. The optimized problem is formulated as compliance minimization with volume and fundamental frequency constraints via semidefinite programming (SDP), and the compliance and fundamental frequency in traditional models are casted as semidefinite matrix constraints, both the cross section and compliance are viewed as variables. In this way, the sensitivity coefficients of multiple eigenvalues are circumvented. The SDP model is applicable both to single and multiple eigenvalues. The theoretical results and the practical use of this model are illustrated by examples at the end of the paper.

Hu D.,Institute of Telecommunication Satellite
Zhongguo Kongjian Kexue Jishu/Chinese Space Science and Technology | Year: 2015

A novel algorithm called Kernel fuzzy C-means imputation (KFCM-I) was proposed for the incomplete data of satellite reaction wheel. The centers and radius of the known fault samples were clustered by the KFCM, and the incomplete data points were replaced by the chosen data points for keeping the sample data completely, which were chosen from the known fault data by the similarity calculation and were the most similar to the incomplete data point. Then the similarity was adopted to diagnose the test sample data. Two scenarios were considered, one was that all the feature data missed at the same time, and the other was that each data missed at the random time, but the locations of all the missing data points were random. Compared with directly excluding the outlier or missing data points in engineering, when the missing data is less than 13% of the total test data, the accuracy of KFCM-I is higher than 90%, while the missing data is between 13%~20%, the accuracy also achieves at 80%. The KFCM-I algorithm is more accuracy and has low computation, which is an useful reference to the engineering. ©, 2015, Chinese Academy of Space Technology. All right reserved.

Zhou J.,Beijing Institute of Technology | Lu Q.,Beijing Institute of Technology | Liu F.,Beijing Institute of Technology | Li Y.,Institute of Telecommunication Satellite
PLoS ONE | Year: 2016

Because of the importance of ultra-wideband (UWB) radar in various applications, short pulse generation in UWB systems has attracted a lot of attention in recent years. In order to shorten the pulse, nonlinear transmission line (NLTL) is imported, which expands the application of step recovery diode (SRD) for pulse generation. Detailed analysis and equations for this SRD and NLTL-based pulse generation are provided and verified by simulation and experimental results. Factors that could cause pulse waveform distortions are also analyzed. The generator circuit presented in this paper generates 130ps and 3.3V pulse, which can be used in UWB radar systems that require sub-nanosecond pulses. © 2016 Zhou et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Liu L.,China Academy of Space Technology | Liu L.,Institute of Telecommunication Satellite | Shan J.,York University | Zhang Y.,DFH Satellite Co. | Zhang Y.,Research and Development Center
Journal of Spacecraft and Rockets | Year: 2016

Large deployable hoop-truss antennas are widely used in satellite communication systems for their high antenna gain and small packed volume. Knowledge of the deployment dynamics of the large deployable hoop-truss antenna and its coupling with spacecraft attitude motion are essential for the design of deployment mechanisms and attitude control systems. In this paper, a spacecraft with two flexible solar panels, which are reduced by Craig-Bampton component modal synthesis, is modeled by natural coordinate formulation. A large deployable hoop-truss antenna is modeled with the absolute nodal coordinate formulation. Both lead to a constant-mass matrix without the centrifugal and Coriolis forces. The whole dynamics model is used to solve the attitude and the reaction moment during the deployment process. Nonsynchronous deployment phenomena due to the structural flexibility and the decay of the driving force are investigated, and results show that these phenomena can increase the stresses suffered by the hoop truss, which should be considered in the design of a large deployable hoop-truss antenna. Copyright © 2016 by Likun Liu, Jinjun Shan, and Yan Zhang. Published by the American Institute of Aeronautics and Astronautics, Inc.

Zhao J.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion | Zhao J.,Institute of Telecommunication Satellite | Huang W.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion | Zhou Y.,Jiangsu Key Laboratory of New Energy Generation and Power Conversion | Jiao R.,Institute of Telecommunication Satellite
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2014

In recent years, the Z-source inverter and the quasi-Z-source inverter are proposed to solve the limitations of the traditional voltage source inverter, which attract a great deal of attention. However, the shortcomings of those two topologies limit their further developments. Here a new type of tapped inductor quasi-Z-source inverter is researched to achieve higher boost ability and smaller capacitor voltage stress. This paper first proposes the generalized DC side small-signal model by using the state-space averaging method, and analyses the impact of the vary in boost network parameters and shoot-through zero state on the system based on the transfer function. The closed-loop regulator of the DC bus voltage is also designed to improve the dynamic performance of the system. Finally, simulations and experiments are carried out to validate the above characteristics.

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