Nonlinear Smooth Feedback Control of a Three-Pole Active Magnetic Bearing System

In this study, a class of smooth feedback controllers is proposed for the stabilization of a three-pole active magnetic bearing (AMB) system. The three-pole AMB system is strongly nonlinear and nonaffine. Conventional controllers are nonsmooth and complicated, which is difficult for implementation and further study. The proposed smooth controllers are designed utilizing a linear transformation on the system inputs (coil currents). As a result, simple smooth controllers, such as quadratic state feedback controller, can be obtained. The domain of attraction of the origin under the smooth controller is estimated. The proposed smooth controller is verified through both numerical and experimental results.