Passivity based control with robust observer for induction motor

In this paper a solution to the output feedback torque and rotor flux tracking problem for an induction motor model given in the natural frame was proposed. In this approach the design of controller and observer is interlaced, and global stability results for the total system can be proved. It must be pointed out that the existing observer in the literature is simple, with only updating from current error terms in the rotor equations. In this work, we present the design of an observer for a special class of nonlinear systems satisfying some regularity assumptions. A further extension of the design strategy is made to a specific class of multi-output systems which assume stronger nonlinear dependence between the various subsystems.