Robust Control Design to Imbalance Compensation and Automatic Balancing of Magnetic Bearings

A new approach for selecting the weighting matrices of H_infin mixed sensitivity and robustness problem in an active magnetic bearing (AMB) system is presented. First an extended dynamic model of a magnetic bearing is developed in state space form. Then, two separate controllers are designed to solve the problem of imbalance in an AMB system. One controller is used to compensate the imbalance forces by generating electromagnetic forces on the bearing surface to cancel these sinusoidal forces (imbalance compensation). Another controller is used to prevent the generation of imbalance forces by forcing the rotor to rotate around its axis of inertia. Simulation results are presented to compare the performance of the designed controllers with a typical general purpose H_infin controller.