Sensorless sliding mode direct torque control (DTC) of induction motor

A new approach to sensorless field oriented induction motor (IM) drive with a single loop control, which may correspond to DTC without a switching table, is presented. The proposed algorithm, presented in previous work by the author, is based on discrete-time sliding mode (SM) control theory and obtained by using two identical sliding surfaces with defining some part of the motor model as its control input. Benefits of this approach are that it reduces the control loops, generally in two cascaded structures, to a single loop and so that it reduces the computing time and it is also easy to design. On the other hand the performance of a SM current controller, employed to extract the proposed single control loop, is discussed for the direct and indirect type vector control drives of IM. Validity of proposed control schemes are confirmed by computer simulation, which showed both the high performance of the drive systems and their robustness against to some parameter variation.