Improved sensorless control method combining SMO and MRAS for surface PMSM drives

Abstract

This paper proposes a sensorless speed control method combining sliding mode observer (SMO) and model reference adaptive system (MRAS) for the surface permanent magnet synchronous motor drives. This hybrid method can guarantee the convergence of both speed and position estimation simultaneously. In order to eliminate the torque fluctuations and mitigate the influence of harmonic components in the estimated back electromotive force (back-eMF) for SMO, a frequency variable stator current tracker (FVT) based on output regulation is proposed. It can estimate the back-EMF accurately. The improved control method provides high accuracy in estimating the rotor position and speed. Simulation results are provided to further validate the proposed rotor position and speed estimation schemes under different speed. It is worth of mentioning that the improved control method can still maintain high estimation accuracy of rotor speed and position at low speed.