Pneumatic Servo Bearing Actuator for Ultraprecise Positioning – Part 2: a New Approach to Ultra-precision Motion Control

INTRODUCTION Externally pressurized gas-lubricated thrust bearings (aerostatic bearings) keep the bearing clearance constant under a constant supply pressure. We investigated how controlling the supply pressure with an electro-pneumatic servovalve can be used to dynamically adjust the bearing gap height. As a result of our investigation, we developed an electropneumatic servo-actuator “pneumatic servo bearing actuator (PSBA)” for position control, force control, and acceleration control. This paper describes a new approach to ultraprecise positioning that uses PSBAs with multiple-layered thin bearing pads in a tandem arrangement. The wide range of potential uses of PSBAs requires the use of bearing pads with diameters ranging from small to large, or a bearing with various numbers of the layered pads. We tested the load capacity of single-pad, 3layered-pad, 10-layered-pad, and 30-layeredpad PSBAs. We also tested the dynamic response of the ten-layered-pad actuator.