A State-Threshold Sliding Mode Control with Improved Extended State Observer for PMSM Speed Control

This paper proposes a novel state-threshold-based sliding mode reaching law integrated with an improved extended state observer (IESO). The method aims to enhance the dynamic response performance of permanent magnet synchronous motor (PMSM) under load disturbances and model mismatch. First, a state-threshold-based reaching law (STRL) is developed for sliding mode control. This threshold-based strategy allows the proposed STRL to respond rapidly to large disturbances while maintaining high sensitivity to small disturbances. This design effectively suppresses control chattering and enhances system robustness against disturbances. Then, an IESO is designed to estimate the total disturbances to further enhance dynamic response capability. The IESO also can reduce the impact of sensor noise by estimating the disturbances and adaptively adjusting the observer gain based on estimated disturbances. By integrating the advantages of STRL and IESO, the proposed STRL+IESO method enhances disturbance rejection capability and preserves a rapid dynamic response. Experimental validation on the PMSM speed control loop confirms its effectiveness, showing improved robustness and faster convergence.