A robust rotor flux observer of induction motor with unknown rotor and stator resistance

The perturbation of the motor parameters degrades the flux observer and the controller. This paper proposes a novel robust flux observer with the resistance uncertainty taken into account. By Extended State Observer (ESO) method, which extends the entire disturbance to a new state, the rotor flux and the variation of rotor resistance are obtained. This is a new kind of state observer constructive method with a special nonlinear and non-smooth feedback. For the variable stator resistance, a simple self-tuning law is designed, which is derived from the dynamic model of the induction motor. The stator resistance value is updated in the ESO. Simulations at high and low frequency illustrate the robustness of the presented method.