A novel variable exponential reaching law-based nonlinear integral sliding mode control for surface-mounted permanent magnet synchronous motors

Surface-mounted Permanent Magnet Synchronous Motors (SPMSMs) are key components in industrial servo drives, due to their high precision and efficiency. However, their performance is often degraded by parameter variations and load disturbances, leading to poor robustness and slow response. To address integral saturation and chattering, this paper proposes a Nonlinear Integral Sliding Mode Control with a Variable Exponential Reaching Law (NISMC-VERL). The method features: (1) a nonlinear sliding surface that prevents windup under large errors and improves precision under small errors; (2) a variable exponential reaching law that accelerates convergence when far from the sliding surface and suppresses chattering near it. Experimental results show that the proposed method outperforms conventional techniques in dynamic response, disturbance rejection, and steady-state accuracy, demonstrating its strong potential for industrial applications.