ACTIVE INHERENT RESTRICTOR FOR AIR-BEARING SPINDLES

An active control method for aerostatic bearings is proposed in this p aper. The proposed method employs an active inherent restrictor AIR, ( which was invented by the authors) to control pneumatic pressure on th e bearing surface. The AIR consists of a piezoelectric actuator with a through hole, one end of which is small enough to function as an orif ice when the actuator is embedded in the bearing to be controlled. Nin e AIRs are incorporated into the aerostatic radial and thrust bearings of an air bearing spindle. According to the radial and/or thrust disp lacements of the spindle detected by sensors, a microcomputer changes the length of the piezoelectric actuators for controlling the orifice area of the AIRs and for compensating the displacements. Thus, the sti ffness and the rotational accuracy in both radial and thrust direction s can be improved without the occurrence of pneumatic hammer. Instead of ordinary passive inherent restrictors, the AIR can be incorporated into most conventional aerostatic bearings. An example of retrofit of the AIR to a commercially available air bearing spindle is also shown. (C) Elsevier Science Inc., 1996