AN OUTPUT-FEEDBACK GLOBALLY STABLE CONTROLLER FOR INDUCTION-MOTORS

We present here a globally stable nonlinear dynamic output feedback controller for torque tracking and flux regulation of induction motors. The control law is globally defined (even in startup), requires only measurement of stator variables and rotor speed, and does not rely on cancellation of the systems nonlinearities. Our work extends in several directions the result of the paper by Ortega et al., where the torque tracking problem was solved for a model where the variables are expressed in a frame rotating at an arbitrary angular frequency (dq model). First, we obviate the need to transfer the dq control signals of the paper by Ortega et al., to the physical input variables in the stator frame, hence providing a directly implementable control law. Second, besides the torque tracking objective, we include the practically important rotor flux regulation task. Third, by choosing a more suitable representation of the motor model, we simplify the controller structure and provide a better understanding of its derivation and behavior.