This paper addresses the feasibility of fuzzy logic control of active magnetic bearing in order to suppress the vibration of the shaft while running at the critical speeds. Three fuzzy controllers were synthesized. The first controller uses the displacements at the bearings as inputs, while the second controller includes the displacements as well as the change of displacements at the bearings as inputs. The third i s a fuzzy proportional integral controller. The capability of the controllers, to compensate the losses occurred in the operating current, were tested. The results showed that the fuzzy proportional integral controller eliminates the shaft deflections but its performance was degraded as the operating current losses increased. The other two fuzzy controllers resulted in an acceptable performance with respect to the damping of the shaft deflections. They also were capable to compensate up to 40% of the current losses. The commonly used proportional derivative controller rendered the worst dynamic performance as compared to the fuzzy controllers.

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