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Keywords:

  • double-column machining center;
  • linear motor;
  • cogging force;
  • force ripple;
  • mechanical deflection;
  • tracking accuracy

Abstract

This paper presents the technologies for high-precision machining with high-speed and high-acceleration driving of feed-axis of double-column machining centers. In the proposed approach, linear motors whose stator has no magnet are adopted to the feed-axis to realize the high-speed and high-acceleration driving. In addition, the characteristic of generating little heat is necessary for this linear motor to keep out thermal deformations of the machine structure. In the proposed approach, the force pulsation of linear motor is reduced by arranging magnets and canceling effects of two sliders. As a result, the motor position can be controled with high accuracy. Moreover, the high-acceleration causes deflections of the machine structure such as a column. The deflections cause tracking errors at the cutting point of the tool, even if the motor position follows the position command correctly. Then, we propose to adopt the feedforward compensation based on the measured mechanical deflections. Experimental verifications using MCR-H (double-column machining center) show the significant performance improvement of the proposed method. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.