H∞ control of Active Magnetic Bearings using closed loop identification model

The Active Magnetic Bearings-supported rotor offer unique advantages in many applications, and it also pose a challenging control problem due to rotor-speed dependence, dynamics coupling, and nonlinear nature of the system. Closed loop identification experiments are done to identify the models at different speeds, and the model uncertainty bound is deduced for controller design. H_∞ controller is then synthesized to guarantee (through the specification of loop-shaping weights) closed-loop robustness and performance with the identified uncertainty bound at the designed rotational speed range. Results through numerical simulations show that the robustness against the uncertainty and the nominal performance for output disturbance rejection of the controller satisfy the design requirements.