Development of a magnetically suspended double-layered cylinder with 1-DOF active positioning control

Abstract

A magnetically levitated double-layered cylinder has been developed for windage loss reduction of the high speed spindle that is rotating inside the inner cylinder. An axial position of each cylinder is actively controlled whereas radial and tilting motions are passively stabilized by the magnetic coupling between the cylinder and the stator. Based on the finite-element-method (FEM) analysis results, a prototype machine was built and tested. When the spindle was driven at 12000 rpm, the magnetically suspended inner cylinder was rotated at 4500 rpm. It is demonstrated that the magnetically levitated cylinder is effective for windage loss reduction when the spindle speed was more than 8000 rpm.