Research on Sensorless Control of PMSM Based on Fuzzy Sliding Mode Observer

In the sensorless control system of permanent magnet synchronous motor (PMSM), the feedback accuracy of rotor position and speed affects the dynamic performance of the system. The sliding mode observer (SMO) can be used to observe the rotor position and speed effectively. To reduce the chattering and improve the observation accuracy, the fuzzy control and SMO are combined first in the paper, and the fuzzy sliding mode gain is designed to be adaptively changed according to the system state. Then a low-pass filter (LPF) whose cutoff frequency is variable with speed is used to filter the extended electromotive force (EEMF) observed by the SMO. In this way, the improved SMO is more suitable for different operating states of the motor. Besides, the paper analyzes the superiority of the method over the conventional SMO theoretically. Finally, it is verified through simulation that the proposed control strategy without position sensor can effectively weaken the system chattering and improve the observation accuracy of rotor position and speed.