Sensorless control of permanent magnet synchronous motor based on sliding mode observer

A novel sensorless control strategy based on a new sliding mode observer (SMO) for permanent magnet synchronous motor (PMSM) is proposed in this paper. Compared with traditional SMO, the sign function is replaced by a sigmoid function to weaken the inherent chattering problem and increase estimation accuracy of the rotor position. To achieve better filtering effect, a two-order low-pass filter is designed to obtain the smooth and accurate back electromotive force (back-EMF). The stability of the proposed SMO is demonstrated using the Lyapunov stability method. Simulation results on a PMSM are provided to verify the effectiveness and robustness of the proposed control strategy.