Adaptive interconnected observer for induction machine in presence of nonlinear magnetic characteristic

The problem of state estimation in induction motors is considered. Generally, the motor observer design is dealt with, based on standard models ignoring the saturation effect of the magnetic characteristic. As a matter of fact, magnetic saturation cannot be ignored especially when considering (speed, torque) control strategies that involve large flux variations. Such large variations are necessary to meet optimal operation conditions in presence of wide range load torque changes. On the other hand, it is well known that the use of mechanical (speed, torque) sensors leads to reliability issues. In this paper, a new adaptive observer design is developed for induction machine, based on a model that accounts for the nonlinear feature of the magnetic circuit. The observer provides estimates of the mechanical and magnetic variables using only stator currents and voltages measurements. The observer convergence is formally analyzed and illustrated by simulation.