Influence of the sign function approximation form on performance of the sliding-mode speed observer for induction motor drive

The paper deals with the speed oscillation reduction methods for the Sliding Mode Observers (SMOs) of the induction motor (IM). The oscillations introduced by the chattering phenomenon can be reduced using the sign function continuous approximation and simple adaptation method. In this method the observer gain is adapted linearly with reference or estimated speed value. Simulation and experimental test results, obtained in a DSP-based control system, are shown to illustrate presented issues.