On the stability of controllers for self-sensing magnetic bearings

A comparison between the controllers using a full-order observer and the reduced-order observer are made from the viewpoint of strong stabilization in self-sensing active magnetic bearings. It is shown that any reduced-order observer based controller stabilizing the plant is unstable while full-order observer based controllers are stable. The self-sensing suspension in magnetic bearings with solid cores is also discussed. It is shown that the controllers are destabilized by a modification of the eddy currents flowing through the cores. It gives the reason for the difficulty of actual self-sensing suspension in the solid-cored magnetic bearing.