Discrete-Time Modeling and Control of Induction Motors by Means of Variational Integrators and Sliding Modes—Part II: Control Design

In this paper, two discrete-time control schemes are presented for induction motors (IMs) based on the discrete-time sliding-mode technique. The first controller is designed using the equivalent control method. The second controller is based on a discrete-time equivalent of the super-twisting algorithm, in which the sliding-mode dynamics is robustified by adding an integral action. The nonmeasurable rotor fluxes are estimated by two observers. The first observer design is based on a simple copy of the rotor flux dynamics, whereas the second observer design is based on the sliding-mode technique. A simulation study was carried out for the evaluation of the closed-loop performance of the IM at different sampling periods and to compare results with other discrete-time control techniques. Moreover, the robust performance of the closed-loop IM is investigated under external and internal perturbations. The simulation study predicts that the IM, when in closed-loop with one of the proposed controllers, still performs well at a sampling time of 1250 μs, whereas other control strategies start to lose accuracy. Real-time experiments were finally carried out, where the good performance of the proposed strategy is verified.