Single coil fault-tolerant control for axial magnetic bearing based on feedback linearization and guaranteed cost control

Axial magnetic bearing has a lower load capacity and enhanced nonlinear characteristics when there is no current in one of the coils of magnetic bearing. In order to increase the load capacity and to stabilize the rotor successfully, a combined fault-tolerant control strategy was proposed integrated by feedback linearization and guaranteed cost control. First, an axial nonlinear dynamic model of axial magnetic bearing-rotor system was established, and it is linearized in a wide range by feedback linearization method. Then, on the basis of varied parameters, an optimal guaranteed cost controller was designed to control the rotor to be suspended in stability and robustness. Finally, several kinds of experiments were performed on the magnetically suspended rotor when there was no current in one of the coils. Obtained results show that the proposed controller can successfully stabilize the rotor when the bearing loads the gravity of rotor. When the parameter is changed by 35%, the peak value of displacement is 2.6 μm, the overshoot is less than 3%, and regulating time is 82 ms. The results demonstrate the validity of proposed controller and show its excellent fault-tolerant control ability and dynamic and static characteristics.