Chen X.,CAS Shanghai Institute of Microsystem and Information Technology |
Chen X.,Shanghai Engineering Center for Micro Satellites |
Zhang R.,Shanghai Engineering Center for Micro Satellites |
Shuai T.,Shanghai Engineering Center for Micro Satellites
Yuhang Xuebao/Journal of Astronautics | Year: 2011
To improve speed and accuracy of the GPS signal acquisition, a new parallel acquisition algorithm based on FFT is proposed. The new algorithm only takes one time of FFT and multiple times of IFFT to complete the two-dimensional search, and operation time reduces the half as compared with that of the traditional algorithm based on FFT. A new algorithm based on polynomial interpolation is proposed to improve the precision of the acquisition accuracy after the coarse acquisition. Simulation results prove it well.
Shang L.,Shanghai Engineering Center for Micro Satellites |
Shang L.,CAS Shanghai Institute of Microsystem and Information Technology |
Liu G.,Shanghai Engineering Center for Micro Satellites |
Zhang R.,Shanghai Engineering Center for Micro Satellites |
Li G.,Shanghai Engineering Center for Micro Satellites
Acta Astronautica | Year: 2013
This paper focuses on the information fusion problem of integrated autonomous orbit determination using the observations from inter-satellite-link (ISL), X-ray pulsars and star sensors. A step Kalman filter structure is proposed to solve the information fusion problem of multiple subsystems that have greatly different filtering precision. The subsystems are grouped according to their measurement accuracy and the state parameters and covariance matrix of a group can be calculated using the federated filter structure and propagated to the next group step-by-step. Simulation results show that the mean user range error (URE) of the constellation will be less than 1.5 m in 60 days using the step Kalman filter structure for information fusion. And it has better performance than the federated structure in dealing with information fusion of the astronomical observations and the ISL ranging measurements in integrated autonomous orbit determination. © 2012 IAA.
Sun S.-Y.,Shanghai Engineering Center for Micro Satellites |
Hu Y.-L.,Space Star Technology |
Chen H.-H.,National Cheng Kung University |
Meng W.-X.,Harbin Institute of Technology
IEEE Transactions on Vehicular Technology | Year: 2016
Owing to ideal correlation properties of complementary codes (CCs), a complementary coded code-division multiple-access (CC-CDMA) system outperforms traditional CDMA systems in terms of its interference-resistance capabilities. However, it may lose its interference-resistance feature and suffer performance degradation over asynchronous frequency-selective fading channels due to the fact that it is incapable of reconstructing ideal complementary cross-correlation functions at a receiver. Based on the analysis on combining and detection algorithms designed for CC-CDMA systems, this paper proposes a joint pre-equalization and adaptive combining scheme. Pre-equalization is used at a transmitter to either enhance diversity gain or compensate channel selectivity leveraged by a controlling parameter ζ, whereas a recursive least square (RLS) adaptive combining algorithm is employed at a receiver to determine the optimal combining coefficients, aiming at minimizing detection errors under different channel conditions. Simulation results show the superiority of the proposed scheme in terms of bit error rate (BER) and its adaptability to varying channel states. © 2016 IEEE.
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.
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.
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.
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.
Li S.,Nanjing University of Aeronautics and Astronautics |
Li S.,University of Strathclyde |
Zhu Y.,Shanghai Engineering Center for Micro Satellites |
Wang Y.,Nanjing University of Aeronautics and Astronautics
Advances in Space Research | Year: 2014
Asteroid deflection techniques are essential in order to protect the Earth from catastrophic impacts by hazardous asteroids. Rapid design and optimization of low-thrust rendezvous/interception trajectories is considered as one of the key technologies to successfully deflect potentially hazardous asteroids. In this paper, we address a general framework for the rapid design and optimization of low-thrust rendezvous/interception trajectories for future asteroid deflection missions. The design and optimization process includes three closely associated steps. Firstly, shape-based approaches and genetic algorithm (GA) are adopted to perform preliminary design, which provides a reasonable initial guess for subsequent accurate optimization. Secondly, Radau pseudospectral method is utilized to transcribe the low-thrust trajectory optimization problem into a discrete nonlinear programming (NLP) problem. Finally, sequential quadratic programming (SQP) is used to efficiently solve the nonlinear programming problem and obtain the optimal low-thrust rendezvous/interception trajectories. The rapid design and optimization algorithms developed in this paper are validated by three simulation cases with different performance indexes and boundary constraints. © 2013 COSPAR.
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.
Yuan G.,Tongji University |
Chen Z.,Shanghai Engineering Center for Micro Satellites
Applied Mechanics and Materials | Year: 2013
Adhesive-bonded composite integrated structures (ACIS) are widely used in civil and military aircrafts now. The failure laws of such structures should be studied obligatorily to design them reasonably. In a composite wing-box test debonding damage was found at the connection between the skin and the wall in mechanical-joint region while the load was added up to certain magnitude. However the shear stress of the adhesive layer in plane was not high. The real reason of the damage is that there is significant out-plane normal tensile stress at the local place. The main factors, which induced out-of-plane normal tensile stress, include out-of-plane force resulting from changing of force transfer path and sudden change stiffness. In this paper an integrated composite I-beam is investigated to expound the existing objectively of out-of-plane force, and analyze the relationships between out-of-plane force, sudden change stiffness and out-plane normal tensile stress or peeling stress. Research indicates that the out-of-plane force and debonding damage resulted from it should be highly valued for ACIS in mechanical-joint region. © (2013) Trans Tech Publications, Switzerland.