Design and experimental test of a speed/flux sliding mode observer for sensorless induction motors

The aim of this paper is to design and experimentally verify a speed/flux sliding mode observer to be used in sensorless control schemes for induction motors. The observer is aimed at replacing the sensors, within the control loop, providing a reliable estimate of the mechanical speed and the flux, in spite of the presence of some kind of uncertainties on the rotor resistance and the applied load torque. The proposed sliding mode observer is based on a different and original approach with respect to the widely used equivalent control-based techniques. More precisely, the observed flux, and, consequently, the observed speed are determined relying on a current observer, instrumentally designed, since the stator currents are actually measurable signals. Simulation and experimental results are reported in the paper to show the satisfactory performances of the proposal.