Supervisory field‐oriented control of induction motors with uncertain rotor resistance

It is well known that the performance of the (industry standard) field‐oriented control (FOC) for induction motors is highly sensitive to uncertainties in the rotor resistance. In this paper we describe how to use supervisory control to obtain an adaptive implementation of FOC for current‐fed machines. The unknown rotor resistance is assumed to belong to a discrete set, while the uncertain load torque ranges in a given compact set. Even though no restrictions area prioriimposed on the size of these sets, their definitions reflect the prior knowledge of the designer, which is effectively incorporated in the supervisory control algorithm. The supervisor selects from these sets values for the parameters to be applied to the FOC, a choice that is made by continuously comparing suitably defined performance signals. We prove that the proposed supervisor achievesglobal stabilizationof the system when the load torque is known to belong to a given finite set of values. Apparently, this is the first globally convergent adaptive algorithm for current‐fed machines which simply adds adaptation to the widely popular FOC and is not a radically new complicated controller, hence it is more likely to be adopted by practitioners. Some simulation results illustrate the properties of the algorithm.