High-Speed Gyroscopic Instability and Cross-Feedback Compensation of a Digitally Controlled Magnetic Bearing

The electromagnetic bearing has high potential of supporting a high-speed rotating shaft. One of the most serious problems is the cross-coupling effect caused by gyroscopic or Fleming force. This paper treats the gyroscopic effect which moves the duplicated resonant poles: one to high and the other to low frequency. Usually the controller has an unstable frequency range caused by integral control or higher delay. The backward precessional motion is apt to be unstabilized by the integral control. A rotationally interrupted cross-coupling control is introduced to compensate for the undesirable precessional motion. This scheme is applied to an active magnetic bearing system, and its capability is tested.