Ultra Precision Positioning using Air Bearing Lead Screw.

In order to realize positioning of nano-meter precision, it is important to eliminate friction and backlash from mechanical parts making relative sliding and/or rolling motion. This paper first describes the principle of an Air Bearing Lead Screw(ABLS)in which the lead screw surface is completely separated from the nut surface by the pressured air film. Then a positioning system comprised of ABLS, a table, an air guideway and air bearings used for supporting the screw shaft is introduced. The system is free from friction except that by DC motor brushes. The basic dynamic characteristics of the system are examined and some controllers are designed and implemented. Experimental results show that the system can position the table with the accuracy of a few nano-meters.