Improving the rotational and transient performance of magnetic bearings by the H∞ DIA control

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 contract-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 hearing, 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 rotational performance, transient response and robust performance.