This paper presents fundamental improvements to the design of a low profile hydrostatic rotary bearing previously reported in [1] and [2] that have resulted in greatly improved tilt stiffness and manufacturability. The new design utilizes horizontally oriented restrictor surfaces, which enhance hydrostatic feedback in the axial and tilt modes of displacement. The design also maximizes bearing area by incorporating an interior drive motor configuration. The result is a 380 mm diameter table which provides radial, axial, and moment stiffnesses of 525 N/micron, 875 N/micron, and 17 N-m/micro-radian, respectively, at an operating pressure of 17 Bar. This bearing has demonstrated a seven fold increase in tilt stiffness versus the previous motorized table [2] of similar size. Similar to its predecessors, the current unit provides sub 0.1 micron radial and axial error motions. Only five principal parts make up the bearing and structure, a consequence of the inherent simplicity of the design.
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