Global adaptive output feedback control of induction motors with uncertain rotor resistance

Abstract

We design for the first time a global adaptive output feedback control for induction motors, which guarantees asymptotic tracking of smooth speed references only on the basis of speed and stator current measurements, for any initial condition and for any unknown constant value of torque load and rotor resistance. These two parameters are the only ones which largely vary during operations. The proposed 7th order nonlinear compensator generates estimates both for the unknown parameters (torque load and rotor resistance) and for the unmeasured states (rotor flux); they converge to the corresponding true values under persistency of excitation which actually holds in physical operating conditions.