NONLINEAR CONTROL OF INDUCTION-MOTORS - TORQUE TRACKING WITH UNKNOWN LOAD DISTURBANCE

In a recent note Ortega and Espinosa [8] presented a globally stable c ontroller for torque regulation of a complete induction motor model wi th partial state feedback, i.e., no assumption of flux measurement. Th e result was established under the assumptions that both the desired a nd load torques are constant, that the former does not exceed certain bounds which depend on the systems natural damping, and that the motor parameters are known. In the present contributions we extend these re sults in several directions. First, by ''adding mechanical damping'' t o the closed-loop system we relax the upper bound condition on the des ired torque. Second, we use a new controller structure that allows us to treat the case of time-varying desired torque. Finally, a new estim ator is proposed to handle time-varying (linearly parameterized) unkno wn loads.