H∞ control of the magnetic bearing considering initial state uncertainties

This paper deals with an application of H_∞ control attenuating initial-state uncertainties to the magnetic bearing and examines the H_∞ control problem, which treats a mixed Disturbance and an Initial-state uncertainty Attenuation (DIA) control. The mixed H_∞ DIA problem supplies H_∞ controls with good transients and assures H_∞ controls of robustness against initial-state uncertainty. On the other hand, active magnetic bearings allow contact-free suspension of rotors and they are used for various industrial purposes. We derive a mathematical model of the magnetic bearing which has complicated rotor dynamics and nonlinear magnetic property. Then we apply this proposed H_∞ DIA control for the magnetic bearing, and design a robust H_∞ controller both for exogenous disturbances and for initial state uncertainties of the plant. Experimental results show that the proposed robust control approach is effective for improving transient response and robust performance.