NEW CONCEPTS FOR COST-EFFECTIVE MAGNETIC BEARING CONTROL

Contact-free active magnetic bearings usually rely on position sensors for stabilization of the highly unstable open-loop plant. New types of active (i.e. controlled) electromagnetic bearings are presented. The sensing is based on current measurement and flux measurement. Two types have been successfully realized: the first type uses current measurement only, the second type uses small Hall probes for flux sensing in the actuator air-gap. No gap sensors are used. Compared to the present active magnetic bearings with gap sensors, savings of space and costs can result. A further advantage is the inherent collocation of sensing and actuator. Practical examples are given and experiments prove the feasibility and robustness of such systems. The net result can be summarized as substitution of hardware through software, creating a potential for increased cost efficiency for some magnetic levitation applications.