Speed sensorless sliding mode torque control of induction motor

Novel induction motor control optimizing both torque response and efficiency is proposed, The control is quite different than the conventional field-oriented control. First, the produced torque is explicitly continuous output variable of control plant. Second, a new rotor flux observer, which allows speed sensorless operation of induction motor (IM) by low and zero speed, was developed. Control is executed in a,b-coordinates (stator frame) and transformation is performed only with the use of observed transformation angle of rotor flux. The proposed approach addresses the problems of torque and flux control without the measurement of the speed of the motor, i.e. speed sensorless drive. Such a control strategy differs from the conventional field oriented control approach. The torque and the stator and rotor flux are controlled instead of the components of stator current i/sub sd/ and i/sub sq/. A new stator and rotor flux observer based on sliding mode control and Lyapunov theory are developed. The output of the closed-loop rotor flux determines the magnitude and orientation angle of the field orientation of induction motor. Simulations and experimental tests on a 1.5 kW motor drive are provided to evaluate the consistency and the performance of the proposed control technique.