A passive speed observer for induction motor

In this paper, the speed observer design problem for induction motors is approached by means of an estimation technique which exploits some properties of the error dynamics that make feasible to express this system as a feedback interconnection, subject to a disturbance signal, of two subsystems that can be rendered passive via a proper choice of the output injection terms. Then, a semiglobal convergent low order observer, which simultaneously estimates rotor fluxes and motor speed in presence of unknown constant load torque, is proposed. Passive speed observer performance is experimentally evaluated and compared with results obtained under the same conditions for an observer based on a model reference adaptive system technique.