Magnetically preloaded aerostatic guideway for high speed nanometer positioning

Abstract

Demands for nanometer positioning with a high resolution and a long stroke have increased in a variety of industries. Performance of guide elements is one of the most important issues for realizing such positioning systems. In general, an ultra-precision positioning system has aerostatic guideway which can restrain a moving table without non-linear behavior, i.e., friction and backlash. Characteristics of aerostatic guideway affect the performance of the positioning system. This study is aiming at developing an aerostatic guideway which can achieve a high speed nanometer positioning. The aerostatic guideway preloaded by magnetic attraction force can lead to provide a compact structure, and the characteristics can be easily controlled without increased driving force. However, the relative velocity between permanent magnets and the attracted surface causes the induced eddy current, which deteriorates the performance during high speed positioning. In this study, in order to minimize the eddy current loss, the magnetic attraction force is successfully added to a mechanism following the positioning table. In order to evaluate the proposed structure, a positioning system is developed by using the magnetic attraction force preloaded aerostatic guideway. The positioning system is constructed by a positioning table and a following table. Basic characteristics of the aerostatic guideway are experimentally evaluated. From the results, the magnetic attraction force-preloaded guideway can be designed so as to obtain high stiffness. By optimizing the magnetic force, the performance of the positioning system was evaluated. The experimental results of frequency response confirm that the response of the positioning system can be improved by applying magnetic attraction force. In addition, the results of stepwise positioning confirm that the proposed positioning system has high positioning resolution. These results confirm that the proposed guideway achieves high speed nanometer positioning capability.