Output Regulation in Magnetic Bearing Systems by a Dynamic Output Feedback Controller

Abstract

This paper deals with the problem of an unbalance vibration in magnetic bearings. Firstly, by assuming that the rotor with an unbalance is a rigid body, we develop a rigorous modeling of a magnetic bearing system in which the rotation of the rotor is (not on its geometrical axis, but) on its axis of inertia. In result, it is shown that, when the rotor rotates around its axis of inertia, sinusoidal disturbances due to the unbalance of the rotor affect the system dynamics and the measured output. These disturbances can be described as the output of the autonomous system. In this case, a part of the state variables of the system to be controlled cannot be measured. Here, our objective is to construct a controller which preserves internal stability and rejects the above-stated disturbances in a wide speed range. The problem is formulated and solved within a framework of the so-called “output regulator with internal stability” theory. The state variables which can not be available are estimated with a minimal order observer. Finally, we present a numerical example for a fixed rotation speed and a result of its experiment.