Super-twisting sliding mode direct torque contol of induction machine drives

This paper presents a new super-twisting sliding modes direct torque and flux controller (STSM-DTC) for induction motor (IM) drives. The STSM is a second-order (type two) variable-structure control which operates without high-frequency chattering. The proposed STSM scheme is a torque and stator flux magnitude controller implemented in the stator flux reference frame, and it does not employ current controllers as in conventional vector control. This controller contains a design parameter that allows the designer to balance its operation between a linear PI-like behavior and a constant-gain sliding-mode-like behavior. The experimental tests show that the STSM-DTC controller displays very robust behavior, similar to a conventional sliding controller, and it works without notable steady-state chattering, like the PI controller. The paper presents theoretical aspects for the new STSM-DTC control, design and implementation details, and relevant experimental results for a sensorless IM drive. The scheme is compared to a second-order sliding mode controller and a linear PI controller. A robustness assessment against the PI controller is also included.