Adaptive sliding-mode-observer for sensorless induction motor drive using two-time-scale approach

This paper, presents a new sliding-mode-observer design for sensorless vector control of induction motors with rotor resistance estimation using two-time-scale approach. This approach, based on the singular perturbation theory, decomposes the observer error dynamics on two parts; fast part, associated to the stator-current observer, and slow part, associated to the rotor-flux observer. Using this decomposition, the rotor-flux-observer accuracy is guaranteed through the stator-current observer. Consequently, adaptive laws for rotor speed and rotor resistance estimations are easily derived using only measured and estimated stator currents and estimated rotor fluxes. The effectiveness of this new approach has been successfully verified through computer simulations, where the control algorithm is based on the indirect field oriented sliding-mode control.