Sensorless Stabilization of Electrodynamic Thrust Self-Bearing Machines

ElectroDynamic Thrust Self-Bearing Machine (EDTSBM) provide, in addition to the drive function, the passive levitation of the rotor in the axial direction. Such machine can therefore be combined with permanent magnet centering bearings to achieve fully passive levitation, cumulating the benefits of a bearingless machine, with the compactness, reliability and low cost of passive levitation. However, EDTSBM requires damping to counteract the inherent instability of electrodynamic suspensions at high speed. Recent research has shown the possibility of introducing this damping by controlling the d-axis current of EDTSBM incorporating a magnetic circuit in the rotor. Nevertheless, this method requires an additional position sensor which reduces the compactness and reliability of the system. In this context, this paper introduces a sensorless control method of the EDTSBM based exclusively on current measurements. The simulation results presented in the paper demonstrate the robustness of the active stabilization strategy based on this estimation of the axial states of the EDTSBM in the levitation direction.