Vibration rejection in magnetic bearing with improved fault-tolerant controller

The existing theory of fault-tolerant control for magnetic bearings with redundant structure adopts the electromagnetic force (EMF) with bias current linearization, while the rotor at the equilibrium position. In this method, the current distribution matrix (CDM) corresponding to different actuator faults is obtained by numerical calculation process, and the current distribution controller is designed. However, the traditional control method cannot inhibit the vibration of the rotor while at the non-equilibrium position. This paper proposed a method of extending the linearized area of the EMF from the equilibrium point to the non- equilibrium point, and the CMD of the displacement compensation is further solved by the optimization algorithm. Furthermore, a design method of the current distribution controller is proposed, which takes the displacement factor into consideration. Then, an improved fault-tolerant controller is constructed by combining the designed current distributor with the position controller. The simulation and experimental verification are carried out under the conditions of no coil fail, the 8th coil fails and the 6-8th coils fail. The simulation results show that the proposed method can effectively suppress the vibration displacement of the rotor that occurs in the non- equilibrium point, and the maximum vibration suppression occurs in the process of support reconstruction, and the suppression rate reaches 71.4 %. The experimental results further prove that the proposed method can effectively suppress the vibration of the rotor, and the maximum vibration suppression rate of rotor reaches 56.4 %.