Sensorless Control Strategy of a Permanent Magnet Synchronous Motor Based on an Improved Sliding Mode Observer

This paper analyzes the problems and the reasons of high frequency chattering, phase delay, unmanageable with low-speed rotation in the traditional SMO control strategy of the sensor-less control strategy of a permanent magnet synchronous motor based on the traditional sliding mode observer. Aiming at the shortcomings of the above-mentioned traditional SMO control strategy, an improved SMO control strategy is presented by replacing the signum function in the traditional synovial observer with the sigmoid function to reduce the high frequency chattering of the system. Meanwhile, the proposed improved SMO control strategy introduces an adaptive filter to eliminate harmonics and chattering, and adaptively compensates the estimated back-EMF value to reduce the estimation error caused by the phase delay. The improved SMO strategy was tested through Matlab/Simulink simulation and real experiments respectively. The results verified that the improved SMO strategy can significantly reduce chattering and phase delay and achieve good control performance at low speeds, as well as maintain good performance at full speed.