All-Passive-Type Magnetic Bearing System Based on a Sleeping Top

Abstract

It is well known that magnetic levitation using permanent magnets without control is impossible. However, just as in the case of a sleeping top, if the body to be levitated has some amount of rotational velocity, the situation will be changed. In this paper, a new type of system which utilizes both the repulsion force of permanent magnets for vertical levitation and a null-flux coil system for horizontal restoring force is proposed. A method of decreasing the required radial restoring stiffness is given. Asymptotic stability of the top is discussed using eigenvalue analysis. Two different types of eddy current dampers for asymptotic stability are proposed. Some preliminary experimental results are also shown.