Time filter

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Han Z.,Northwestern Polytechnical University | Zhang K.,Northwestern Polytechnical University | Yang T.,China Xian Satellite Control Center
CGNCC 2016 - 2016 IEEE Chinese Guidance, Navigation and Control Conference | Year: 2016

Finite-time convergence control strategies based on adaptive Nonsingular Terminal Sliding Mode are proposed for spacecraft attitude tracking control subject to external disturbances and actuator faults. The designed attitude tracking controller meets the multi-constraints, and has singularities avoidance attributes. It is further shown that the controller with parameter adaptations is independent from bound of external disturbances. The Lyapunov stability analysis shows that the controller designed in this paper can guarantee the fast convergence of the closed-loop system, and has a good fault tolerant performance on actuator faults under the multi-constraints on external disturbances and actuator faults. Numerical simulation verified the good performance of the controller in the attitude tracking control. © 2016 IEEE.


Cao L.,China Xian Satellite Control Center | Li H.,China Xian Satellite Control Center
Journal of Dynamic Systems, Measurement and Control, Transactions of the ASME | Year: 2016

A new set of linearized differential equations governing relative motion of innerformation satellite system (IFSS) is derived with the effects of J2 as well as atmospheric drag. The IFSS consists of the "inner satellite" and the "outer satellite," this special configuration formation endows its some advantages to map the gravity field of earth. For long-term IFSS in elliptical orbit, the high-fidelity set of linearized equations is more convenient than the nonlinear equations for designing formation control system or navigation algorithms. In addition, to avoid the collision between the inner satellite and the outer satellite, the minimum sliding mode error feedback control (MSMEFC) is adopted to perform a real-time control on the outer satellite in the presence of uncertain perturbations from the system and space. The robustness and steady-state error of MSMEFC are also discussed to show its theoretical advantages than traditional sliding mode control (SMC). Finally, numerical simulations are performed to check the fidelity of the proposed equations. Moreover, the efficacy of the MSMEFC is performed to control the IFSS with high precision. Copyright © 2016 by ASME.


Wang D.,Communication University of China | Fan J.,Communication University of China | Li Y.,China Xian Satellite Control Center
Journal of Convergence Information Technology | Year: 2012

LFM signals are widely used in the fields of radar and communication etc., which make signals detection and parameters estimation a very important technology in multicomponent LFM signals. To solve the problems of error detection caused by the cross-terms in WVD-Hough methods and other modified WVD distribution methods, and low parameter estimation precision due to poor timefrequency concentration in S-Hough transform, this paper proposed a detection and parameter estimation algorithm of multicomponent LFM signals based on reassigned generalized S-transform and Hough transform. Firstly calculate the time-frequency distribution of multicomponent LFM signals by generalized S-transform. Secondly reassign the S-transform time-frequency distribution to improve the time-frequency concentration property. Finally implement signal detection and parameter estimation by Hough transform to the reassigned S-transform TFD. The simulation results show that this algorithm has good performance in detecting multicomponent LFM signals and estimating the parameters in low SNR case.


Cao L.,China Xian Satellite Control Center | Li H.,China Xian Satellite Control Center
Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering | Year: 2016

For the attitude estimation problem, the quaternion is preferred to describe the rotation of spacecraft, which obeys a unit-norm constraint. However, this constraint is not considered in the most of the traditional estimation algorithms. This work will develop a new estimator named norm-constrained predictive filter to solve this problem based on the predictive filter frame. The optimization theory of Lagrange multiplier is adopted by minimizing a constrained cost function to improve the traditional predictive filter. In addition, the obtained estimator is further analyzed and applied to the spacecraft attitude estimation problem by numerical simulations. © Institution of Mechanical Engineers.


Cao L.,China Xian Satellite Control Center | Li H.,China Xian Satellite Control Center
Acta Astronautica | Year: 2016

For the satellite attitude estimation problem, the serious model errors always exist and hider the estimation performance of the Attitude Determination and Control System (ACDS), especially for a small satellite with low precision sensors. To deal with this problem, a new algorithm for the attitude estimation, referred to as the unscented predictive variable structure filter (UPVSF) is presented. This strategy is proposed based on the variable structure control concept and unscented transform (UT) sampling method. It can be implemented in real time with an ability to estimate the model errors on-line, in order to improve the state estimation precision. In addition, the model errors in this filter are not restricted only to the Gaussian noises; therefore, it has the advantages to deal with the various kinds of model errors or noises. It is anticipated that the UT sampling strategy can further enhance the robustness and accuracy of the novel UPVSF. Numerical simulations show that the proposed UPVSF is more effective and robustness in dealing with the model errors and low precision sensors compared with the traditional unscented Kalman filter (UKF). © 2016 IAA


Cao L.,China xiAn Satellite Control Center | Li H.,China xiAn Satellite Control Center
Journal of Aerospace Engineering | Year: 2016

A novel cubature predictive filter (CPF) is presented for relative position and attitude estimation of satellite formation taking into account the J2 perturbation. A coupled relative translational dynamics is derived to represent orbital motion of arbitrary feature points on deputy, and the relative attitude motion is formulated by the rotational dynamics for the satellite. Based on the proposed coupled dynamics, the CPF is developed based on the third-degree spherical-radial cubature rule, extending the study of a traditional predictive filter (PF). The algorithm flow of the CPF is proposed first. Then, it is demonstrated that the estimated accuracy of the model error and system state for CPF is higher than that of traditional PF. In addition, a cubature Kalman filter (CKF) is also employed in order to evaluate the performance of the proposed CPF. Several different scenarios are simulated to validate the effectiveness of the coupled dynamics model and the performance of the proposed CPF. Through comparisons, the proposed CPF is shown to yield to obtain more accurate relative position and attitude estimation for satellite formation. © 2015 American Society of Civil Engineers.


Cao L.,China Xian Satellite Control Center | Chen X.,National University of Defense Technology
Science China Information Sciences | Year: 2016

In this paper, the cubature predictive filter (CPF) is derived based on a third-degree spherical-radial cubature rule. It provides a set of cubature-points scaling linearly with the state-vector dimension, which makes it possible to numerically compute multivariate moment integrals encountered in the nonlinear predictive filter (PF). In order to facilitate the new method, the algorithm CPF is given firstly. Then, the theoretical analyses demonstrate that the estimated accuracy of the model error and system for the proposed CPF is higher than that of the traditional PF. Moreover, the authors analyze the stochastic boundedness and the error behavior of CPF for general nonlinear systems in a stochastic framework. In particular, the theoretical results present that the estimation error remains bounded and the covariance keeps stable if the system’s initial estimation error, disturbing noise terms as well as the model error are small enough, which is the core part of the CPF theory. All of the results have been demonstrated by numerical simulations for a nonlinear example system. © 2016, Science China Press and Springer-Verlag Berlin Heidelberg.


Cao L.,China Xian Satellite Control Center | Chen X.,National University of Defense Technology
Journal of Computational and Nonlinear Dynamics | Year: 2016

A novel input-output linearization minimum sliding mode error feedback control (I/OMSMEFC) is proposed for the synchronization between two uncoupled FitzHugh-Nagumo (FHN) neurons with different ionic currents and external electrical stimulations. To estimate and offset the system uncertainties and external disturbances, the concept of equivalent control error is introduced, which is the key to utilization of I/OMSMEFC. A cost function is formulated on the basis of the principle of minimum sliding mode covariance constraint; then the equivalent control error is estimated and fed back. It is shown that the proposed I/OMSMEFC can compensate various kinds of system uncertainties and external disturbances. Meanwhile, it can reduce the steady-state error more than the conventional sliding mode control (SMC). In addition, the sliding mode after the I/OMSMEFC will tend to be the ideal SMC, resulting in improved control performance and quantity. Sufficient conditions are given based on the Lyapunov stability theorem and numerical simulations are performed to verify the effectiveness of presented I/OMSMEFC for the chaotic synchronization accurately. © 2016 by ASME.


Cao L.,China Xian Satellite Control Center | Chen X.,National University of Defense Technology
Science China Information Sciences | Year: 2016

With the recent flurry of the research on Inner-Formation satellite system, there has been apparent need for a set of linearized equations to describe the relative motion of satellites under the effect of the J2 geopotential disturbance, which is the important perturbed-factor for low-orbit Inner-Formation system. Hence, on the assumption of small eccentricity, a new set of linearized equations of motion is proposed that accounts for J2 perturbations in an elliptical orbit. To avoid the collision between the inner satellite and the outer satellite, the Minimum Sliding Mode Error Feedback Control (MSMEFC) is developed to perform a real-time control on the outer satellite with the uncertain perturbations from the space. The highlight of MSMEFC is to introduce the concept of equivalent control error, which is the key utilization of MSMEFC. It is shown that the proposed MSMEFC can compensate any kinds of uncertain perturbations. Besides, in this paper, the relationship between the equivalent control error and uncertain perturbations is discussed. The robustness and steady-state error of MSMEFC are also analyzed to show its theoretical advantages compared with traditional SMC. Numerical simulations are employed to check the fidelity of the linearized equations. In addition, the efficacy of MSMEFC is verified by the utilization of Inner-Formation system with high control precision. © 2016 Science China Press and Springer-Verlag Berlin Heidelberg


Cao L.,China Xian Satellite Control Center | Chen X.,National University of Defense Technology
Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering | Year: 2015

Under the existence of system uncertainties and external disturbances, complete synchronization of chaotic systems is achieved by introducing a novel input-output linearization minimum sliding mode error feedback control with high control precision, which is based on the input-output linearization method and sliding mode control. In the literature, the magnitudes of bounded nonlinear dynamics of synchronous error system were required in the designed sliding mode controller. In this study, this article proposed a new approach to estimate the various uncertainties and disturbances on the basis of chaotic system. To facilitate the analysis, the concept of equivalent control error is introduced, which is the key to the utilization of input-output linearization minimum sliding mode error feedback control. A cost function is formulated on the basis of the principle of minimum sliding mode covariance constraint; then, the equivalent control error is estimated and fed back to the conventional sliding mode. It is shown that the sliding mode after the input-output linearization minimum sliding mode error feedback control will approximate to the ideal sliding mode, resulting in improved control performance and quality. Finally, the chaotic gyro system and chaotic FitzHugh-Nagumo neurons system have been employed to verify the proposed controller. Sufficient conditions to guarantee stable synchronization are given and the numerical simulations of complete synchronization of the two chaotic systems are performed to verify the effectiveness of the presented schemes. © 2015 Institution of Mechanical Engineers.

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