Robust Tracking Control for Permanent Magnet Linear Synchronous Motors With Unknown Uncertainties via Sliding Mode Approach

This paper proposes a novel robust super-twisting nonsingular fast terminal sliding mode control method for high precision position tracking of permanent magnet linear synchronous motor (PMLSM). Based on the position tracking error of PMLSM, a nonsingular fast terminal sliding mode variable is constructed to avoid the singularity and achieve the convergence of the position error in a finite time. To improve the convergence speed of the super-twisting algorithm and solve the gain overestimation problem of the existing algorithm, a dual-layer nested adaptive adjustment law based on the super-twisting scheme is proposed, which does not need the information of the unknown uncertainties. While ensuring that the conditions of the existence of the sliding mode hold, the control gain is made as small as possible to obtain a continuous switching control law to suppress the effect of the chattering phenomenon. The Lyapunov stability proves the robustness and convergence of the system. Experimental results confirm the effectiveness and feasibility of the designed position tracking control scheme.