Fuzzy control scheme for dual-acting magnetic bearing actuator system

Active magnetic bearings are increasingly being utilized in rotating machinery applications as an alternative to the conventional rolling-clement and fluid-film bearing types. Magnetic bearing is an open-loop unstable system, and in most practical applications, a PID controller is utilized to ensure stable operation of the rotating machinery. The PID controller, however, becomes ineffective when the machine operates in highly nonlinear regimes. This paper develops a fuzzy logic control scheme to improve the performance of a dual-acting magnetic bearing actuator system operating in nonlinear regimes. The nonlinearity in this system is due to the relationship between the forces generated in the electromagnetic actuator and the coil current and the air gap between the rotor and the stator. The dynamic response of the magnetic bearing actuator system based on the fuzzy logic scheme proposed in this work was found to be much better as compared to the response of the system based on the conventional PD controller. The fuzzy logic control scheme presented in this work may be used for the nonlinear control of systems that operates in nonlinear regimes.