Nonlinear observation strategies for induction motors

This paper deals with nonlinear observation of missing states in induction motors. A general nonlinear observer is firstly introduced. Then, several specialized versions of this observer are considered for the estimation of nonmeasured states in induction motors. Indeed, two situations, depending on whether the rotor speed is measured or not, are particularly emphasized. In the first one, the stator currents and the motor speed are supposed to be measured and a nonlinear observer of the variety we propose is used for the on-line estimation of the rotor fluxes and the load torque. In the second situation, only the rotor currents measurements are supposed to be available and again, a specialized version of the proposed general observer is used to estimate the rotor fluxes, the motor speed and the load torque. Simulation results are given in order to illustrate the performance of the proposed observers.