Magnetic Bearings for Precision Linear Slides

Abstract

Early uses of scanning tunneling microscopes indicate that many areas of science could greatly benefit if centimeter scale objects could be probed on an atomic scale. This could be accomplished by the development of a linear slide having one Angstrom resolution and a one-tenth meter range of travel. Magnetic suspension technology has been proposed as an ideal candidate for the suspension of the linear slide. This technology is attractive since it combines low noise, excellent positioning accuracy, zero wear, and requires no lubrication. The paper examines the feasibility of developing a magnetic suspension with a required resolution exceeding one Angstrom and establishes the requirements for this suspension. The achievable resolution is shown to be determined by position measurement accuracy, suspension gain, suspension bandwidth, and disturbance force levels. Expected disturbance force levels from ground motion, air currents, and acoustic effects are projected. Given the expected disturbance force levels, measurement accuracy, and required controller performance, a magnetic suspension could be developed which would provide resolution better than the one Angstrom required.