A Unifying Point of View of Controllers for Active Magnetic Bearings

This paper investigates the fundamental properties of active magnetic bearing controllers from the standpoint of output regulation in the presence of deterministic disturbances. The treated disturbances are stepwise and unbalance forces acting on the rotor. A transfer function approach is used in the analysis. The general structures of controllers achieving displacement or current regulation for stepwise force and achieving displacement, current or force regulation for unbalance force are derived. The mutual relations and equivalence between the independently developed controllers are clarified. A direct synthesis method of constructing controllers achieving specified performances is also shown based on these analyses.