This paper proposes a novel composite sliding mode control strategy to enhance the robustness and precision of surface-mounted permanent magnet synchronous motor (SPMSM) speed regulation under internal parameter variations and external load disturbances. The approach integrates a Composite Adaptive Reaching Law (CARL) with a Sliding Mode Observer (SMO). CARL dynamically adjusts the sliding mode gain based on system state variations and incorporates a disturbance-compensating damping term, effectively reducing chattering and improving disturbance resilience. Additionally, the SMO estimates disturbances in real time, and feeds them back into the speed control loop, lowering the switching gain and further suppress chattering. Comprehensive simulation and experimental validation confirm the proposed method's superior performance, demonstrating its potential for high-performance motor control applications.

reaching law, SPMSM, sliding mode control, chattering, disturbance observer