Rotor position estimation based on modified sliding mode observer for sensorless permanent magnet synchronous motor

A novel sensorless speed control algorithm based on sliding mode observer (SMO) for permanent magnet synchronous motors (PMSM) is proposed. By utilizing a phase locked loop algorithm (PLL) based on synchronous reference frame and an embedded low pass filter, the drawback of SMO called “chattering phenomenon” is effectively attenuated, with no phase delay caused by the filter. The active back electromotive force (ABEMF) is normalized to simplify the design of regulators. The influence of the motor parameter variation on the stability of the algorithm is analyzed in detail, and the relationship between the parameter variation and the position estimated error is obtained. The experimental results show the validity of the theoretical analysis and the feasibility of the estimation strategy.