In the medium and high speed range applications, the sensorless speed control of PMSM based on the back EMF are reliable as well as low cost. This paper proposes a simplified sliding mode observer to obtain precise rotor position and applies a closed-loop current regulator in startup process. The method can meet different load conditions and smoothly transition to the double closed-loop sensorless vector control state. The entire control strategy has features of simple structure and high robustness. It only requires little computing power and is suitable for low-cost microchips. The validity of the proposed control method is verified on a PMSM experimental platform.

permanent magnet synchronous motors(PMSM); sensorless sliding mode observer; IF startup ; optimized transition strategy.