Enhancement of the speed response of PMSM sensorless control using an improved adaptive sliding mode observer

This paper propose an adaptive sliding mode observer(SMO) which adds an estimation function for the stator resistance to the conventional sliding mode observer. It is proposed for the robust sensorless control of permanent magnet synchronous motor(PMSM) with variable parameters. The low-pass filter and additional position compensation of the rotor are used to reduce the chattering problem commonly found in the conventional sliding mode observer. It became possible by applying the sigmoid function with the control of a switching function. With the estimation function for the stator resistance, the proposed observer can improve the performance in the estimation of the motor’s speed by reducing the estimation error in the fast adjustment even in the situation that the stator resistance is varied by the element of the sensorless operation. Also this control system has better efficiency than the traditional adaptive sliding mode observer as it reduces the integral calculus computing. The stability of the proposed adaptive sliding mode observer is verified by the Lyapunov function in determining the observer gain, and the validity of the observer is demonstrated by simulations and experiments.