Observer Scheme for State and Parameter Estimation in Asynchronous Motors with Application to Speed Control

The paper presents a method for simultaneous state and parameter estimation in induction motors, based on an exact Kalman-like observer. The use of such an observer is made possible by an immersion of the nonlinear model of the machine into a model which is affine with respect to the variables to be estimated. This method can be used in various cases of unknown variables to be estimated, from the most simple case when only the stator flux components are unknown, to some “worst” case when all the electrical parameters, along with the stator flux angular velocity and load torque are to be estimated. In any case, global exponential estimation is guaranteed under appropriate excitation, following Kalman theory. In practice, the method is evaluated through simulations within an estimate-based speed control scheme.