Active Magnetic Bearing System Equipped with a Fuzzy Logic Controller

This paper proposes an intelligent control method for positioning an active magnetic bearing (AMB) system, by using emerging fuzzy logic controller (FLC) approaches. An AMB system depends on controlling the air gap between the stator and the rotor. In practice, no precise mathematical model can be established because the rotor displacement in an AMB system is inherently unstable, and the relationship between the current and electromagnetic force is highly nonlinear. Nearly all industrial applications of AMBs are still based on conventional proportionalintegral-derivative or proportional-derivative controllers. Recently, fuzzy logic has been used as a mathematical tool for addressing the uncertainties in human perception and reasoning. It also provides a framework for applying approximate human reasoning capabilities to knowledge-based systems. This study designed a closed-loop decentralized FLC for an AMB system. The control algorithm was numerically evaluated to construct a multiple-input multiple-output mathematical model of the controlled system. The membership functions and rule design of the FLC were based on the mathematical model of an AMB system. The simulation results for the AMB system indicated that the system responded by demonstrating satisfactory control performance without overshoot, maintaining a zero-error steady state, and exhibiting a short rise time. The proposed controller can be feasibly applied to AMB systems exhibiting various external disturbances and the FLC with capacities operates effectively in a wide range of shaft positions.