ALL-PASSIVE-TYPE ROTARY MAGNETIC BEARING SYSTEM BASED ON STABILITY PRINCIPLE OF SLEEPING TOPS

It is well known that magnetic levitation using permanent magnets with out control is impossible. However, just as in the case of a sleeping top, if the body to be levitated has rotational velocity, the situatio n will be changed. In this paper, a new type of system which utilizes both magnetic force of permanent magnets for vertical levitation and a null-flux coil system for axial or radial restoring force is proposed . A method of decreasing the required restoring stiffness for the null -flux system is given. Asymptotic stability of the top is discussed us ing eigenvalue analysis. Damping methods for the asymptotic stability of two conical vibration modes using eddy current dampers and the null -flux system are proposed. From preliminary experimental results, the possibility of constructing the all-passive-type rotary magnetic beari ng is clarified.