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Magnetically levitated six degree of freedom micro-machining rotary table

University of British Columbia

This thesis presents a six degree of freedom magnetically levitated rotary table that has one unlimited rotation axis. The actuation force is achieved by the Lorentz force. The underside of the actuator has an axial Halbach array mounted circumferentially near the outside edge. Force is produced in the stator coils which are made using a printed circuit board. The purpose of this table is for a micro-machining rotary table application. Benefits of this table are its compact, lightweight, no friction and high precision characteristics. Control of the table in six degrees of freedom is achieved by dividing the stator into quarters. Each quarter is driven by a linear three phase current amplifier. For each quarter two forces can be generated, one in the levitation direction and one in the tangential direction. This creates eight independently controlled forces allowing for full six degrees of freedom control. Position feedback for the stage is achieved by using four capacitive displacement measurement probes and four optical encoders around a circular optical grating. Performance of the table has been tested and the results show that the closed loop bandwidth for all axes is between ∼ 250Hz and ∼ 550Hz. Regulation error in the X,Y and Z axes is less than 55nm while the A,B and C axes are better than 1.2µrad (0.248 arc seconds). Force capacity has been tested up-to 70N with a theoretical limit of 140N.

Text

2015-06-30

Attribution-NonCommercial-NoDerivs 2.5 Canada

http://hdl.handle.net/2429/51753

Mechanical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/2.5/ca/