Sensorless Indirect Field Oriented Control of induction motors with rotor resistance adaptation

This paper presents a controller for speed-sensorless induction motors which is adaptive with respect to the rotor resistance. The non-adaptive solution presented by the authors in Automatica, vol. 42, no. 10, October 2006 is revised to plug-in a rotor resistance adaptation mechanism. The solution presented in this paper provides local asymptotic speed and flux amplitude tracking together with local asymptotic field orientation and asymptotic convergence of rotor resistance and load torque estimation, under assumptions of unknown and constant rotor resistance and load torque and provided that a physically meaningful persistency of excitation condition is satisfied. No simplifying hypothesis such as the knowledge of stator fluxes, pure integration of the stator flux dynamics or stator current differentiation are introduced. The speed-flux controller is based on the Improved Indirect Field Oriented Control approach, while the speed is estimated by a high-gain reduced-order speed observer. The rotor resistance adaptation law is designed taking into account the peculiarities of the original non-adaptive solution. The achievable performances are tested by simulation.