Finite-Time Adaptive Second-Order Sliding Mode Speed Control Method With Enhanced Disturbance Rejection for SPMSM

To enhance the speed tracking accuracy and robustness of surface-mounted Permanent Magnet Synchronous Motor (SPMSM) under uncertain disturbances, a new adaptive second-order sliding mode (NASOSM) speed control method is proposed. First, the dynamic model of SPMSM under uncertainties is established, a new adaptive SOSM speed controller incorporating a power integrator is constructed, which ensures the finite-time stability. Compared with the traditional fixed gain SOSM controller, the proposed controller ensures that the SPMSM maintains strong robustness against uncertainties without compromising steady-state performance, and the speed tracking error converges in finite-time to the predetermined region independent of the initial system state. By incorporating a second derivative term, the control channel uncertainty is reduced. Second, a new nonlinear disturbance observer (NDOB) is designed to estimate uncertainties in real-time. Nonlinear functions are introduced to replace the linear terms in the extended state observer (ESO) accelerating the convergence of the observation error to zero, further enhancing disturbance rejection and alleviating chattering. Furthermore, the NASOSM speed controller integrated with the NDOB enhances the response speed of system state far from equilibrium, and avoids overestimation of controller gain, which is rigorously analyzed via Lyapunov theory. Finally, experimental results validate that the proposed control method significantly improves both the transient and steady-state performance of the SPMSM under various operating conditions.