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Yu S.-J.,Shanghai Engineering Center for Micro Satellites | Cheng Y.-Q.,China Aerodynamics Research And Development Center | Qian W.-Q.,China Aerodynamics Research And Development Center
Yuhang Xuebao/Journal of Astronautics | Year: 2011

Reentry body transonic aerodynamic parameter online identification methods are researched, and an augmented extended kalman filter is used as the online identification tools. Effect of the augmented extended kalman filter approach on joint state and parameter estimation is overall analyzed, and it is found that slowly varying parameters are well estimated, but estimate values for fast varying parameters are largely divergent. To overcome this disadvantage, a new kind of strong tracking filter is introduced into the traditional augmented extended kalman filter, the simulation shows that strong tracking filter can effectively overcome the disadvantage of larger estimation error for general augmented extended kalman filter. Source

Zhang Y.,Soochow University of China | Wang P.,Soochow University of China | Guo C.,Shanghai Engineering Center for Micro Satellites
Polymer Composites | Year: 2016

This article presented the energy absorption behaviors and damage mechanisms of 3D braided composites under transverse impact and low-velocity impact with frequency domain analysis method. The transverse impact tests were contracted by modified split Hopkinson pressure bar with the impact velocities of 13.6, 17.8, and 22.8 m/s. The low-velocity impact tests were performed by Instron 9250 drop-weight instrument with the impact velocities ranging from 1 to 6 m/s. The experimental results shown that the peak load, displacement to peak load, total energy absorption increased with the increase of impact velocity. The damage morphologies showed the failure mode of 3D braided composite. Increased with the impact velocity, the failure mode changed from resin crack to fiber breakage. The frequency domain analysis results showed that the amplitude of stress wave increased with the increase of impact velocity, but its corresponding frequency was irrelevant to impact velocity. The different amplitude regions corresponded to different failure mode. © 2014 Society of Plastics Engineers. Source

Gong W.-B.,Shanghai Engineering Center for Micro Satellites
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2010

To meet the requirements of large system capacity and miniaturized terminal of mobile satellite communication, Multi-beam array antenna is adopted to realize the high gain and wide coverage by LEO satellite. This paper presents a planar transmitter array antenna with equal flux density coverage according to CDMA standard utilized by LEO satellite. The phased array antenna consists of an array antenna with 61 micro-strip elements, 61 RF front ends, and digital beam forming network (BFN). Orthogonal transform and phase-amplitude adjustment are completed in digital BFN. The 61-channel IF signals outputted by digital BFN are up-converted and amplified by RF front ends, finally transmitted by array antenna to realize the desired shaped-beam coverage. The design methodology and measured results of DBF phased array antenna is discussed in the paper. The measurements demonstrate that all the parameters of array antenna are consistent with the predefined requirements, which validates the rationality of system design and project implementation. Source

Yang Y.,Nanjing University of Aeronautics and Astronautics | Zhou J.,Nanjing University of Aeronautics and Astronautics | Chen J.,Nanjing University of Aeronautics and Astronautics | Mo Q.,Shanghai Engineering Center for Micro Satellites
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2014

In order to improve the low intercept performance of a datalink, a burst communication datalink model based on conditional maximum entropy is proposed in this paper. In this model, the prior datas are used as the training sample space, and lagrange multipliers are selected as optimized variables. Hybrid chaotic particle swarm optimization (HCPSO) algorithm is used for the optimization of the model, and the HCPSO takes the dual programming of the conditional maximum entropy as its objective function, and ultimately determines the conditional maximum entropy probability distribution model. Compared with the single threshold method (STM) and double threshold method (DTM), the simulation results show that the proposed maximum entropy method (MEM) can not only effectively increase the uncertainty of the transmitting moment, but also ensures longer effective communication time and better environment adaptability. Therefore, MEM demonstrates better comprehensive performance than both STM and DTM. Source

Xiong Z.,Nanjing University of Aeronautics and Astronautics | Yao X.,Nanjing University of Aeronautics and Astronautics | Yao X.,Shanghai Engineering Center for Micro Satellites | Yu F.,Nanjing University of Aeronautics and Astronautics
Nanjing Hangkong Hangtian Daxue Xuebao/Journal of Nanjing University of Aeronautics and Astronautics | Year: 2013

Research is conducted, for the security and reliability of the failed satellite's on-orbit operation, on the position and attitude estimation of the failed satellite in the close-distance approach. On the basis of the analysis on the characteristic and the motion mode of the failed satellite, the observation model of a stereo vision system based on the feature point of the failed satellite surface is not only connected with relative position and attitude, but also has some links with the chaser satellite's position and attitude. Thus, a method of relative position and attitude is proposed as well as the chaser satellite's position and attitude in this paper. First, the relative position, the relative attitude, the chaser satellite's position, and the chaser satellite's attitude are established. Then, according to the state model, and the observed model of the stereo vision system, GPS, star sensor, and extended Kalman filter are designed. Finally, the simulation shows that: relative position and attitude of the two satellites are estimated, and the chaser satellite's position and attitude are also estimated at the same time, which show high precision. Source

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