Sensorless speed and position estimation of PMSM using sliding mode observers in γ-δ reference frame

In this paper a simple sensorless algorithm of estimating the permanent magnet synchronous motor (PMSM) speed and position is presented. The proposed approach introduces a new PMSM mathematical model considered in an estimated gamma-delta reference frame instead of stationary alpha-beta reference frame. A state observer has been implemented by the fundamental excitation method based on sliding mode observer theory. The effectiveness of the proposed method was verified using Matlab/Simulink facility on a salient-pole PMSM. In the simulation, it is assumed that the stator resistance is changed and an external torque disturbance is applied. The overall observation system gives exceptional estimation results at high and low speed ranges, without initial rotor angle knowledge.