Sensorless Control of PMSM with Compensated Sliding Mode Observer

Abstract

This paper presents a research on sensorless control of Permanent-magnet Synchronous Motor (PMSM) based on a compensated sliding mode observer (C-SMO) using one Hall sensor. Generally the sliding mode observer (SMO) has an attractive robustness to disturbances, and parameter variations in relatively high speed region. But the SMO cannot help reducing the ripple or chattering components of the estimated currents and the estimated phase especially in the low speed region. The estimated rotary speed is the differential result of the estimated phase. So the noise of the estimated phase is amplified in the estimated rotary speed which is used in speed closed-loop control and the low pass filter. The PMSM cannot be started with traditional SMO under closed-loop control condition. A more accurate estimated speed and a phase reference may solve this problem and they can be estimated by the Hall sensor. This more accurate estimated speed can also help the PMSM achieve a better performance on rotor phase estimation. The C-SMO which combines the advantages of Hall sensor and SMO achieves a less noise, less vibration effect. And the PMSM can be started with C-SMO under closed-loop control condition. The comparison between the SMO and C-SMO is realized by Matlab/Simulink and the simulation results show the effectiveness of the proposed algorithm for the sensorless drive system of a PMSM.