On Discrete-Time Control of Current-fed Induction Motors

In this short paper we present a discrete-time eld oriented controller (FOC) for current-fed induction motors which insures global asymptotic speed regulation as well as rotor ux norm tracking. To the best of our knowledge, this is the rst time such a result is rigourously established for a controller implemented in discrete-time. To insure global stability a condition on the reference for the rotor ux norm, which is time-varying, is imposed. This condition disappears as the sampling period goes to zero, hence allowing for independent speed regulation and rotor ux norm tracking. One important feature of our scheme is that, compared with the rst diierence approximation of the classical indirect FOC, the additional computational burden is negligible. It is also shown that the result can be easily extended to the case of tracking time-varying references in speed or position.