A second-order nonlinear disturbance observer based non- singular terminal sliding mode control for PMSLM system

Abstract In this paper, a speed-current single-loop control strategy for permanent magnet synchronous linear motors (PMSLM) with load variations is investigated. Firstly, a second-order model of the PMSLM is developed by combining the speed and q-axis current. Then, a speed regulation strategy consisting of a non-singular terminal sliding mode control and second-order nonlinear disturbance observers is designed for the developed second-order model to improve the response and disturbance rejection performance of the PMSLM. The matched and mismatched disturbances of the second-order model are estimated by second-order nonlinear disturbance observers. The convergence of the studied control strategies is analysed by the Lyapunov theory. Finally, the simulation and experimental results show the advantages of the studied control strategy in terms of response and robustness compared to the PID and SMC based on cascade structure.