Robust Direct Field Oriented Control of Induction Motors Using Adaptive Observer

This paper deals with the simultaneous estimation of the rotor flux and the rotor resistance of induction motors by a modified Luenberger observer. The proposed observer assumes that only the motor speed and the stator currents are measured. Its corrective terms are based on the derivative of stator currents. The use of the Lyapunov's theory for the flux observer stability analysis permits to give an adaptive law for the on-line rotor resistance estimation. This observer is combined with a direct field oriented control to achieve a robust speed and flux control. Simulation results are presented to evaluate the performances of this control-observer structure scheme