Selfsensing unbalance rejection and reduction of the gyroscopic effect for an active magnetic bearing system

The unbalance of a magnetically levitated rotor causes synchronous oscillations in the current and position signals. This oscillations can lead to saturation of the magnetic actuator. To deal with that problem a selfsensing unbalance controller is developed to reduce the unbalance oscillations in the current signals. The selfsensing unbalance controller consists of two parts. The first part is the unbalance observer which has the task to detect the angular velocity and the angle of the synchronous unbalance information. The second part is the unbalance controller which uses the information of the unbalance observer to reject the unbalance oscillations in the current signal. For the unbalance controller a two modulation step Notch filter is used. The unbalance controller is not the only device which needs the angular velocity. With the angular velocity information also a parameter variant control path can be developed which has the task to reduce the gyroscopic effect. The last part of this paper deals with experimental results of the proposed control system which is implemented on an industrial magnetic bearing system.