Fault-tolerant control of three-pole active magnetic bearing

Active magnetic bearings have many advantages over conventional bearings due to contactless operation and adjustable force dynamics. However, one of the obstacles associated with these bearings is failure modes, which may result in destructive rotor dynamic behaviour. One of the important failure modes is electric power outage which may be due to failure of power amplifier, coil or electric wiring. In the present work, a fault tolerant controller has been designed for three-pole magnetic bearings to provide unaltered performance in the event of fault occurrence. The controller has been designed by incorporating the nonlinear fuzzy logic control. The present design of fuzzy logic controller is done by reducing the number of rules of its rule base. Simulations have been carried out to test the performance of the controller for different failure conditions. The designed controller is able to stabilize the rotor for large deviations from the origin even in the presence of failure. The controller is found to be robust as it provides satisfactory operation in the presence of uncertainties.