Robust Detection for Demagnetization Fault in the Permanent-Magnet Synchronous Motor Using Improved Sliding-Mode Observer

This paper investigates a robust detection for demagnetization fault in the permanent-magnet synchronous motor (PMSM). A proportional-integral fading sliding-mode observer (PIFSMO) is proposed, which can solve the problem of PMSM performance degradation caused by the permanent-magnet demagnetization and resistance disturbance increase during long-term operation. A PMSM demagnetization model is established, and an improved PIFSMO is proposed to detect the demagnetization flux linkage. A fading integral term is added to the traditional sliding-mode observer, which can suppress the offset in the resistance disturbance estimation caused by transients, thereby achieving direct estimation of the resistance disturbance and the slowly varying resistance disturbance (e.g., ḋ≠0) in particular. Simulation and experimental results demonstrate the feasibility and effectiveness of the proposal.