PMSM sensorless speed estimation based on sliding mode observers

A new sensorless method of estimating the permanent magnet synchronous motor speed is presented. The method is based on sliding mode observer theory using Lyapunov stability criteria. The observation algorithm makes use of the machine model equations allowing the estimation of flux/current, stator resistance, rotor angle and rotor speed from the motor terminal measurement of currents and voltages. Speed/position observer is based on a modified back EMF state observer, which is considered in cascade with stator flux/current and resistance observers. The presented application has been implemented using an estimated gamma-delta reference frame instead of alpha-beta stationary reference frame. It is shown that the overall observation system gives exceptional estimation results at high and low speed ranges, without initial rotor angle knowledge. Simulation results of permanent magnet synchronous motor sensorless speed estimation are also presented.