Adaptive forced balancing for magnetic bearing control systems

Active magnetic bearings (AMBs) support shafts or rotors without any mechanical contract. They require feedback control for robust stabilization and performance. A problem common to all mechanical systems with rotating shafts, including AMB systems, is the synchronous vibration caused by mass unbalance. Autobalancing compensation causes AMB actuators to spin a rotor about its inertial axis and thus eliminate the centrifugal forces due to mass unbalance. An autobalancing method, called adaptive forced balancing (AFB), with unique features, including negligible effect on bandwidth and stability margin and no need for a dynamic plant model, is introduced. AFB is implemented on a digital signal processor as part of a complete feedback controller stabilizing a single-end suspension, AMB rig. The experimental results show that AFB realizes at least 30 dB reduction in actuator control current. Simulations verify that stability and desired bandwidth remain intact when AFB compensation is used