Flow rate control for constant film thickness of hydrostatic bearing system

Abstract

Restriction or constant flow is utilized to compensate recess pressures of a hydrostatic bearing which can be highest load capacity than any other type bearing, but not stiffness. Like to other type bearings supporting the worktable that is displaced continuously with changing load. This study proposes a control scheme with both feedbacks of flow rate and film thickness and measurements of temperature and pressure for constant thickness of hydrostatic film. The control algorithm of this scheme results in changing pump speed by using PID controller. As long as film thickness is controlled to be constant, worktable can be kept stable without steady-state displacement when load is changing. The steady-state accuracy in few sub-microns can be achieved by PID controller using the algorithm of this study, which have been verified by numerical simulation and measurement in experiments.