Time filter

Source Type

Liu H.-Q.,Shanghai Institute of Satellite Engineering | Wang L.V.,Shanghai Institute of Satellite Engineering | Wang L.V.,Tsinghua University
Journal of Physics: Conference Series | Year: 2017

The composite control strategy of CA-CMAC and ILC is adopted to solve the inverse kinematic problem of the redundant DOF manipulator during its real-time and high-precision tracking on the three-dimensional space target trajectory. A direct inverse model control strategy is adopted, in which CA-CMAC takes the current joint angles and the desired position increment of the manipulator as the input, and estimates the expected joint angle increments of the manipulator using the system history control experience. Then the estimated joint angles are taken as the initial value of the ILC module by which the control effect is improved iteratively. Based on the MATLAB, the tracking controls of linear and circular space target trajectories were simulated respectively. The results show that CA-CAMC and ILC composite control has better tracking precision and stability than CMAC control, while keeping the joint angles of the manipulator continuous and smooth during trajectory tracking. © Published under licence by IOP Publishing Ltd.


Jiang R.,Shanghai JiaoTong University | Chen J.,Shanghai JiaoTong University | Dong G.,Shanghai JiaoTong University | Liu T.,Shanghai JiaoTong University | Xiao W.,Shanghai Institute of Satellite Engineering
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2013

In vibration analysis, weak fault detect and diagnosis is of great importance. A method based on minimum entropy deconvolution and envelop spectrum analysis is proposed in this article. Minimum entropy deconvolution technique searches for an optimal set of filter coefficients to enhance the impulse making the filtered signal to contain clearer fault information. When there is a fault in bearing, it can be obviously reflected by the power spectral density estimation of the filtered signal even if the power spectral density estimation of original signal denies the information. The filtered signals are then analyzed by performing envelop spectrum analysis, where the bearing characteristic frequencies are quite clear for further diagnosis. The feasibility and validity of utilizing the minimum entropy deconvolution in weak fault diagnosis and condition monitoring is demonstrated by both simulation and experiments. The analysis of actual data from accelerated life test of rolling bearing shows that it can detect and diagnose fault 7 min earlier than RMS can reflect while the entire life takes 1962 min. This is considered to be significant in condition monitoring and early incipient fault diagnosis. The results of gearbox test also demonstrates the effective bearing fault diagnosis under strong noise and gear vibration interactions. © 2012 IMechE.


Li F.,Shanghai JiaoTong University | Peng H.,Shanghai Institute of Satellite Engineering | Meng G.,Shanghai JiaoTong University
Sensors and Actuators, A: Physical | Year: 2014

A circular PZT ceramic wafer array based on a process of receiver beamforming is developed for damage identification in plate structures, and a method of quantitative damage image construction is presented using Lamb wave signals received from the array. Design parameters of the circular PZT array, including diameter of the PZT array, number of PZT wafers and steering angle, are investigated. Characteristics related to magnitude of the array response, viz. the reflection coefficient and distance between the damage and the array, are also analyzed. It is demonstrated that, because of the unique configuration of the PZT array, the magnitude of the array response is independent of the direction of the damage location relevant to the array. Exact propagation path of wave propagation is adopted, and therefore the damage can be reconstructed even in the near field surrounding the PZT array. To validate the proposed method, a circular PZT array consisting of one PZT actuator and several PZT sensors is used in experiments to identify damage in an aluminum plate. By considering the attenuation of Lamb wave propagation in plate structures, quantitative image construction is implemented for damage of different severities and distances from the array. © 2014 Elsevier B.V.


Dong G.,Shanghai JiaoTong University | Chen J.,Shanghai JiaoTong University | Zhao F.,Shanghai Institute of Satellite Engineering
Journal of Sound and Vibration | Year: 2015

This paper is in the field of vibration based fault diagnosis for rolling element bearings, where one major issue is the ability to detect faults as early as possible. Bispectrum analysis has been applied in bearing diagnosis. In this paper, a frequency-shifted bispectrum is studied for bearing diagnosis. It is found that the frequency-shifted bispectrum is more suitable for analyzing amplitude modulated and frequency modulated signals than the bispectrum, when choosing the carrier frequency as the specific frequency shift value. For bearing vibration signals with amplitude modulation characteristics, in which the carrier frequencies are structural resonant frequencies, one of the structural resonances can be chosen as the specific frequency shift value for the frequency-shifted bispectrum analysis. To increase diagnostic ability of the frequency-shifted bispectrum for bearing faults, firstly, the frequency resolution is increased in the frequency-shifted bispectrum analysis through band pass filtering and frequency zooming; secondly, integration of the frequency-shifted bispectrum along one frequency variable is used to produce a one-dimensional spectral representation. Numerical simulation and experimental results show the feasibility of the proposed method for qualitatively and quantitatively diagnosing bearing faults. © 2014 Elsevier Ltd.


Cong F.,Shanghai JiaoTong University | Chen J.,Shanghai JiaoTong University | Dong G.,Shanghai JiaoTong University | Zhao F.,Shanghai Institute of Satellite Engineering
Mechanical Systems and Signal Processing | Year: 2013

Rolling element bearing faults are among the main causes of rotating machines breakdown. It is important to distinguish the incipient fault before the bearings step into serious failure. Based on the traditional singular value decomposition (SVD) theory, short-time matrix series (STMS) and singular value ratio (SVR) are introduced to the vibration signal processing. The proposed signal processing method is called S-SVDR (STMS based SVD method using SVR) and it has been proved to have a good local identification capability in the rolling bearing fault diagnosis. The detailed description of applying S-SVDR methods to rolling bearing fault diagnosis is given through the artificial fault signal processing in experiment 1. In experiment 2, rolling element bearing accelerated life test is performed in Hangzhou Bearing Test & Research Center (HBRC). The experimental result shows that the incipient fault can be well detected through S-SVDR processing method. However, the envelope analysis of original signal cannot detect the fault due to the existence of signal interference. A conclusion can be made that the proposed S-SVDR method has a good effect on de-noising and eliminating the signal interference of rolling bearing for the fault diagnosis. © 2012 Elsevier Ltd.


Li K.,Shanghai Institute of Satellite Engineering
Proceedings of the International Astronautical Congress, IAC | Year: 2013

Most of space satellites have large structures, solar array paddles and antennas, are folded during transport into space by launch vehicles, and deployed after arriving in space which could cause platform vibration. Satellite vibration monitoring is a problem of great complexity. Wireless sensor network can be used to sample and gather the vibration data of the satellite. For wireless vibration measurements, time synchronization is important because the vibration data are simultaneously measured at multipoint sensor nodes and are transmitted via multi-hop relayed to base station. However most of the current algorithms mainly focus on the precision of synchronization. In fact, in the context of space, stability and robustness of WSN is the key matter of concern. In this paper, a novel multi-hop time synchronization scheme is proposed with the purpose of improving its robustness and stability. The experiments results illustrate our scheme can achieve good precision in the presence of problematic nodes. Copyright ©2013 by the International Astronautical Federation.


Tang Z.,Dalian University of Technology | Liu S.,Dalian University of Technology | Zhang Z.,Dalian University of Technology | Zhang Z.,Shanghai Institute of Satellite Engineering
Thin-Walled Structures | Year: 2013

A type of cylindrical multi-cell column is proposed to improve energy absorption performance, which is inspired by the phenomenon that the circular tube is more efficient than the square tube in energy absorption. This type of structure shows high performance in energy absorption for its considerable number of corners on the cross section and the angles between neighbor flanges are in the optimal range as well as some more efficient cylindrical shells have been adopted. Numerical examples illustrate that cylindrical multi-cell column is more efficient than square column and square multi-cell column in energy absorption. In addition, a parametric study considering the effects of geometrical parameters on the structural crashworthiness has been carried out. And it is found that wall thickness, the number of cells alone the radial and circumferential directions have a distinct effect on the energy absorption. © 2012 Elsevier Ltd. All rights reserved.


Qin W.,Harbin Institute of Technology | Fang B.,Shanghai Institute of Satellite Engineering | Lu S.,Harbin Institute of Technology | Wang Z.,Harbin Institute of Technology | And 3 more authors.
RSC Advances | Year: 2015

A strategy of reinforced PPy wrapping over an acetylene black-coated sulfur composite (PPy-AB/S) was designed for synthesizing cathode materials of Li-S batteries with improved performance. It was found that the resulting PPy-AB/S cathodes were able to maintain 630 mA h g-1 even after 200 charge-discharge cycles at a rate of 0.5 C. © The Royal Society of Chemistry 2015.


Li S.,Nanjing University of Aeronautics and Astronautics | Peng Y.,Shanghai Institute of Satellite Engineering
Advances in Space Research | Year: 2012

In order to accurately deliver an entry vehicle through the Martian atmosphere to the prescribed parachute deployment point, active Mars entry guidance is essential. This paper addresses the issue of Mars atmospheric entry guidance using the command generator tracker (CGT) based direct model reference adaptive control to reduce the adverse effect of the bounded uncertainties on atmospheric density and aerodynamic coefficients. Firstly, the nominal drag acceleration profile meeting a variety of constraints is planned off-line in the longitudinal plane as the reference model to track. Then, the CGT based direct model reference adaptive controller and the feed-forward compensator are designed to robustly track the aforementioned reference drag acceleration profile and to effectively reduce the downrange error. Afterwards, the heading alignment logic is adopted in the lateral plane to reduce the crossrange error. Finally, the validity of the guidance algorithm proposed in this paper is confirmed by Monte Carlo simulation analysis. © 2011 COSPAR. Published by Elsevier Ltd. All rights reserved.


Li S.,Nanjing University of Aeronautics and Astronautics | Peng Y.-M.,Shanghai Institute of Satellite Engineering
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering | Year: 2012

To deliver a Mars entry vehicle through the Martian atmosphere to the prescribed parachute deployment point, active Mars entry guidance and control is essential. This article addresses the problem of Mars atmospheric entry control by a neural network-based sliding mode variable structure control (NNSMVSC) to reduce the effect of the bounded uncertainties on the atmospheric density and aerodynamic coefficients. First, NNSMVSC is designed to robustly track the prescribed nominal trajectory under high uncertainties and to effectively reduce the downrange error. Then, the heading alignment logic is adopted in the lateral plane to reduce the cross-range error. Finally, the validity of the control algorithm proposed in this article is demonstrated by computer simulation analysis. © IMechE 2011.

Loading Shanghai Institute of Satellite Engineering collaborators
Loading Shanghai Institute of Satellite Engineering collaborators