Direct torque control of permanent magnet synchronous motor using a sliding-mode observer

This paper proposes that direct torque control of interior permanent magnet synchronous motors (IPMSM) using a sliding mode observer (SMO). The sigmoid function is used to decrease the chattering as the switching model. This function is more effective than the unit step function to decrease the chattering. The back-EMF component of the motor is observed for robust sensorless control. The rotor position is detected from the observed back-EMF component and phase-locked loop method for estimating accurate position of the rotor and speed of the motor is applied. The validity of the proposed control scheme through simulations is confirmed.