Sliding Mode Active Disturbance Rejection Composite Control for Sensorless Low-Speed Operation of PMLSM Using Low-Frequency Injection Method

The traditional low-frequency signal injection method has good low-speed steady-state performance and parameter robustness in sensorless control of surface-mounted permanent magnet synchronous motor (PMSM). This paper extends it and establishes a low-frequency current injection model suitable for permanent magnet linear synchronous motor (PMLSM). However, its low-frequency characteristics lead to insufficient dynamic response and disturbance rejection performance. Therefore, a sliding mode active disturbance rejection composite control strategy integrating a time-varying gain nonlinear reaching law is proposed: Firstly, a new reaching law with dynamic convergence characteristics is designed to optimize the convergence speed and chattering of sliding mode control (SMC); Secondly, an extended state observer (ESO) is combined to construct an active disturbance rejection structure to estimate and compensate for the disturbances of the system. Simulation and experimental results show that the proposed low-frequency current injection method for PMLSM and its improved method can achieve stable operation under low-speed sensorless conditions.