Adaptive online rotor resistance identification for bearingless induction motors

Bearingless induction motors always suffer from the influence of rotor resistance variations.An adaptive online rotor resistance identification method is developed here based on an observer of the suspension force commands.This study analyzes the influence of the rotor resistance variation on the air-gap flux identification.Real-time online identification of the rotor resistance is based on observations of the suspension force commands,which utilizes the principle that the suspension force commands are sensitive to the air-gap flux in the torque windings.Tests of a bearingless induction motor show that the peak-peak displacements of the rotor are reduced by 60% by this adaptive online rotor resistance identification method.