Magnetic Bearing With Rotating Force Control

Abstract

A common attractive type active Magnetic Bearing (AMB) was designed and tested with three parallel feedback control loops. The feedback of the measured AMB journal displacement provides the bearing stiffness. Two special circuits, called Velocity Observer and Acceleration Observer, are formulated for estimating the AMB journal velocity and acceleration based on the same measured displacement without performing differentiation. The feedback control using the estimated velocity provides the AMB damping. The feedback control using the estimated acceleration creates a rotating force which cancels the imbalance force and other external disturbances. The rotating force control can be switched on or off in the designed speed range without causing rotor instability. This additional vibration suppression mechanism greatly enchances the versatility of AMB.