Sliding mode observer for wide-speed sensorless control of PMSM drives

Many of the estimation techniques developed to achieve speed or position sensorless, motor drives suffer from the variation of motor parameters such as the stator resistance, stator inductance or torque constant. In particular, conventional linear estimators are not adaptive to variations of the operating point. The sliding mode technique has shown promising results when estimating or controlling nonlinear systems. This paper presents a sliding mode observer (SMO) for estimating the position and speed of a permanent magnet synchronous motor (PMSM) to achieve sensorless drive system. The technique can be generalized to other motor drives and motion control systems. The effects of the variation of motor parameters such as stator resistance and stator inductance on the position and/or speed estimations, over a wide speed range, have been studied. Compared to other methods, the observer is more robust to parameter detuning. Simulations results are presented.