H/sub /spl infin// control of the magnetic bearing considering initial state uncertainties

Abstract

This paper deals with an application of H/sub /spl infin// control attenuating initial-state uncertainties to the magnetic bearing and examines the H/sub /spl infin// control problem, which treats a mixed Disturbance and an Initial-state uncertainty Attenuation (DIA) control. The mixed H/sub /spl infin// DIA problem supplies H/sub /spl infin// controls with good transients and assures H/sub /spl infin// 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/sub /spl infin// DIA control for the magnetic bearing, and design a robust H/sub /spl infin// 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.