Cross-Feedback Stabilization of the Digitally Controlled Magnetic Bearing

Abstract

A method of stabilizing a high speed rotor supported by magnetic bearings is presented. The magnetic bearing is controlled by a digital controller with rotationally synchronized interruption. The main problem with the rotating disc is the cross-coupling effect caused by the gyroscopic or inductive forces which sometimes make the high speed rotor unstable. Standard PID control is carried out with constant time interval interruption, while the rotational interrupt subroutine performs the cross-coupling feedback. The cross-feedback in the x-y directions well compensates for the undesirable coupling effect. This scheme is applied to a four-mass, two-bearing rotor system and its capability is tested.