Chattering free sliding mode control law for position control of the drive employing induction motor

Principles of forced dynamics control and sliding mode control are combined to derive control algorithm for position control of the drive with induction motor. The controller is of the cascade structure, comprising an inner speed control loop based on forced dynamics control and an outer position control loop based on sliding mode control. The inner speed control loop respects the principles of vector control and requires an estimate of the load torque, which is estimated in an observer. To obtain chattering free position control algorithm smoothing integrator is introduced into outer control loop. For the final version of the sliding mode control law the signum function is replaced by the high gain enabling rearrangement of the block diagram to avoid extra output derivative, which results due to smoothing integrator insertion. The simulations and preliminary experimental results indicate that the proposed control system exhibits the desired robustness and therefore warrants further development and investigation.