Robust Nonsingular Terminal Sliding-Mode Control for Nonlinear Magnetic Bearing System
ABSTRACT This study presents a robust nonsingular terminal sliding-mode control (RNTSMC) system to achieve finite time tracking control (FTTC) for the rotor position in the axial direction of a nonlinear thrust active magnetic bearing (TAMB) system. Compared with conventional sliding-mode control (SMC) with linear sliding surface, terminal sliding-mode control (TSMC) with nonlinear terminal sliding surface provides faster, finite time convergence, and higher control precision. In this study, first, the operating principles and dynamic model of the TAMB system using a linearized electromagnetic force model are introduced. Then, the TSMC system is designed for the TAMB to achieve FTTC. Moreover, in order to overcome the singularity problem of the TSMC, a nonsingular terminal sliding-mode control (NTSMC) system is proposed. Furthermore, since the control characteristics of the TAMB are highly nonlinear and time-varying, the RNTSMC system with a recurrent Hermite neural network (RHNN) uncertainty estimator is proposed to improve the control performance and increase the robustness of the TAMB control system. Using the proposed RNTSMC system, the bound of the lumped uncertainty of the TAMB is not required to be known in advance. Finally, some experimental results for the tracking of various reference trajectories demonstrate the validity of the proposed RNTSMC for practical TAMB applications.
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ABSTRACT: SUMMARYA unified solution is presented to the tracking control problem of Euler–Lagrange systems with finite-time convergence. A reconstruction module is designed to estimate the overall of unmodeled dynamics, disturbance, actuator misalignment, and multiple actuator faults. That reconstruction is accomplished in finite time with zero error. A nonsingular terminal sliding mode controller is then synthesized, and the resultant closed-loop system is also shown to be finite-time stable with the reference trajectory followed in finite time. Unlike most sliding mode control methods to handle system uncertainties, the designed control has less conservativeness and stronger fault tolerant capability. A rigid spacecraft system is used to demonstrate the effectiveness and potential of the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd.International Journal of Robust and Nonlinear Control 10/2014; · 1.90 Impact Factor
- Journal of Guidance Control and Dynamics 03/2014; 37(2):644-657. · 1.15 Impact Factor
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ABSTRACT: This paper deals with the stabilization of a magnetically-levitating shaft using a simple, fast, nonlinear discrete time control approach. The proposed control approach uses an approximate numerical one-step time discretization of the nonlinear plant model behavior obtained from offline simulations. Using that discretization, a control minimizing the distance between the plant output and a reference linear system is computed, leading the system to adopt its dynamical behavior. Since the prediction horizon is limited to one time-step, the execution time of the algorithm can be completely bounded. It can thus easily be implemented and used to control fast electromechanical systems. Experimental results obtained from a laboratory device show the performance and robustness of the proposed controller.2014 European Control Conference (ECC); 06/2014