A sliding mode speed and rotor position estimator for PMSM

The paper discusses the problem of state estimation for the non-salient permanent magnet synchronous motor (PMSM) and presents a method for estimation of speed and rotor position based on a sliding mode (SM) EMF observer. The observer is developed based on the full order PMSM model in the stationary reference frame. The motor speed is a required input in the proposed observer and a speed estimate obtained from the output rotor position is used. The SM observer is analysed using Lyapunov’s theory of non-linear stability and is validated by simulations and experimental tests. The proposed method is applicable in a sensorless PMSM drive; the estimator uses only the measured motor voltages and currents and produces estimates of the speed and rotor position. The influence of the feedback gains of the SM observer is discussed. The method is relatively simple to implement, involves a reduced number of design gains, does not require correction of the rotor position and has excellent accuracy for a wide speed range and at low speed.