Static and dynamic analyisis of inherently compensated aerostatic flat pad bearings

The design of aerostatic bearings is becoming of increasing importance in engineering. As the trend to precision and ultra precision manufacture gains pace and the drive to higher quality and more reliable products continues, the advantages which can be gained from applying aerostatic bearings to machine tools, instrumentation and test rigs is becoming more apparent. Due consideration has to be given to the inlet restrictor design so as to improve the static and the dynamic response of the air bearing. Inherently compensated orifices (also referred to as laminar flow restrictors) although not commonly used in practice due to difficulties encountered in assembly/fabrication of the orifices are known to give highly stable air bearing systems. In this paper we examine the static characteristics and dynamic characteristics of inherently compensated orifice based aerostatic flat pad bearing system. Static performance has been evaluated based on Reynolds equation and mass conservation equation for incompressible flow whilst dynamic performance of the bearing has been evaluated based on same set of equations but based on compressible flow. The change in performance (static and dynamic) of the aerostatic bearing is studied by varying orifice diameter, gap height and supply pressure. A technique to ease the assembly of orifices with the air bearing plate has also been discussed so as to make the manufacturing of the inherently compensated bearings more commercially viable. Key Words: Air Bearing, Static and dynamic performance, Inherent compensation.