PMSM sliding mode observer for speed and position estimation using modified back EMF

Abstract

This paper introduces a novel sensorless method for speed and position estimation of permanent magnet synchronous motor (PMSM). The mathematical model of PMSM is expressed in an arbitrary rotating reference frame and no knowledge of initial rotor position is needed. The developed algorithm is based on sliding mode observer (SMO) theory and consists of two discrete steps: flux/current and speed/position estimation. Also, Lyapunov functions are suitably chosen for determining the adaptive laws for the stator resistance and the speed estimators. First stator flux/current and resistance error converges to zero and afterwards speed and position estimation is carried out using a modified back electromotive force (EMF) observer. Simulation results show the effectiveness of the proposed estimation method.