A Second-order Continuous Sliding Mode Observer for Sensorless Permanent Magnet Synchronous Motor Control

In this paper, a second-order continuous sliding mode back electromotive force (EMF) observer is proposed for sensorless permanent magnet synchronous motor (PMSM) control. Compared to traditional first-order and super twisting sliding mode observer, the proposed strategy can maintain the characteristics of the second-order observer and also smooth the estimated back EMF. Third-order linear extended observer (LESO) is adopted to estimated the position, speed and load torque of PMSM. Compared to arc-tangent function method, LESO does not use low-pass filter, and is less sensitive to high-frequency noise in the estimated back EMF. Meanwhile, the estimated load torque can be used as disturbance compensation for subsequent control. Simulation results have comprehensively illustrated the feasibility and effectiveness of the proposed strategy.