Sliding-mode observer design for sensorless vector control of AC induction motor

In this paper, a sliding-mode observer is applied to control an AC induction motor. First, the modeling of AC induction motor is presented. After that, a sliding mode observer is proposed to estimate the motor speed, the rotor flux, the angular position of the rotor flux and the motor torque from monitored stator voltages and currents. The proposed sliding mode observer provides very good performance for both low and high speed motor operation. Furthermore, the proposed system is robust in motor losses and load variations. The proposed observer does not uses complicated observer gains and it is easy to setup for different types of motor. The convergence of the proposed observer is obtained using the Lyapunov theory. Hardware and software for experiment of the AC induction motor drive are introduced. The experimental results illustrate that fast torque and speed response with small torque ripples can be achieved. The proposed control scheme is suitable to the application fields that require high performance of torque response such as electric vehicles.