Abstract
Advances in various areas of precision mechanics such as semi-conductor exposure apparatus, MEMS/NEMS, nano-imprint lithography devices and other nano-technology applications, have required ultraprecise positioning techniques with nanometer-scale accuracy to be developed. Our laboratory has developed a 'pneumatic servo bearing actuator (PSBA)' as a novel actuator that uses pneumatic servo technology for ultraprecise positioning. The actuator mainly consists of an aerostatic thrust bearing and a pneumatic servo valve. In the actuator, the pressurized air controlled by the servo valve moves an actuated spool supported by the aerostatic bearing ultraprecisely. However, the stroke of developed actuator was short, less than several dozen of micrometer, because the bearing clearance directly corresponded to the displacement of actuated spool. To expand the actuator stroke, the PSBA with multiple thrust bearing pads arranged in laminate structure was newly proposed and developed. The experiment using the developed actuator with thirty bearing pads showed that the actuator stiffness was kept constant even in long stroke up to 150 um and the step response and settling time improved as compared with those of the actuator with a single bearing pad. In addition, we confirmed that the minimum resolution of the actuator was less than 10 nm even without feedback controls, which was enough to meet the demands of current ultraprecise positioning technology.
