Integral sliding-mode direct torque control of sensorless induction motor drives

The paper deals with a full sliding mode approach for induction motor drives direct torque and flux control. The proposed solution is composed by an integral sliding-mode control and by a speed-sensorless sliding mode observer. The suggested Integral Sliding-Mode Direct Torque Control (ISMDTC) is formulated in the stator flux reference frame, without employing current regulators. The adopted sliding mode observer provides stator-flux and torque estimation, without rotor-speed adaptation. The numerical results show that the ISMDTC maintains the robustness of the sliding controller, reducing the chattering during the steady state. Moreover, it consents to achieve similar performance like more complex second-order SMC offering more simple implementation. The ISMDTC assures good accuracy and robustness to parameters deviations at low-speed operations as well as in all the operative range of the IM drives. For proving the goodness of the proposal the suggested control is also compared with a conventional DTC control.