Research on sliding mode variable structure rotational speed observer used in PMSM-DTC

Considering large volume, high cost and low reliability caused by the existence of mechanical sensor in the control system of permanent magnet synchronous motor(PMSM), this paper designed a speed observer instead of mechanical speed sensor based on sliding mode variable structure theory to realize speed sensor-less control of PMSM. Because accurate values of motor voltage and current were needed for sliding mode observer in estimation of rotor position and speed, the SVPWM modulation method was adopted. Simulation and experiments were performed on the basis of system model, and the results indicated that the DTC of PMSM speed sensor-less control based on sliding mode variable structure could significantly reduce the fluctuation of motor torque, flux linkage and current ripple. Besides it had better dynamic and static performance.