Adaptive Terminal Sliding Mode Control for Magnetic Levitation Systems With Enhanced Disturbance Compensation

Abstract

For improving the convergence rate and time-varying disturbance rejection ability, an adaptive nonsingular terminal sliding mode controller based on disturbance compensation technique is proposed to control the position of magnetic levitation system in this article. First, the dynamical model of the magnetic levitation system is deduced, then a nonsingular terminal sliding mode control (NTSMC) is constructed. For reducing the chattering phenomenon, the time-varying disturbance estimation and compensation is cooperated into NTSMC controller using generalized proportional integral observer, the switching gain value could be chosen smaller, it could improve the system disturbance rejection, but the dynamic response is sacrificed to some extent. Thus, the adaptive NTSMC method is proposed for ensuring the dynamic and steady-state performance, the switching gain value could be tuned adaptively depending on the system states. When the system states are far away from the sliding mode surface, the gain value is large, else if the system states convergence to sliding mode surface, the value is small. Simulation and experimental results confirm the closed-loop performance both in dynamic response and disturbance attenuation, corresponding quantitative comparison could also show the advantages of the proposed control scheme.