Linear Output Feedback Control of a Three-Pole Magnetic Bearing

The design and implementation of linear and nonlinear control methods for a three-pole active magnetic bearing (AMB) is presented in this paper. It is shown that the system has nearly linear dynamics by adding a bias to coil currents. A decentralized PID feedback law and an integral sliding mode controller are proposed and the unknown state variables of the system are estimated by the Kalman filter. The optimal gains of the linear controller are determined by the LQG technique. To evaluate the effectiveness of the proposed controllers, they are implemented on an experimental setup. The experimental results show that the proposed methods can effectively stabilize the three-pole AMB. The simplicity of the feedback law, computation time, and inherent robustness of the PID method, which makes it less sensitive to unmatched system uncertainties, are the advantages of the linear controller compared to integral sliding mode method studied in this paper.