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TECHNICAL PAPERS

Multiaxis Maglev Positioner With Nanometer Resolution Over Extended Travel Range

[+] Author and Article Information
Won-jong Kim1

Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123wjkim@tamu.edu

Shobhit Verma

Department of Mechanical Engineering, Texas A&M University, College Station, TX 77843-3123

1

Corresponding author.

J. Dyn. Sys., Meas., Control 129(6), 777-785 (Jan 23, 2007) (9 pages) doi:10.1115/1.2789468 History: Received March 10, 2006; Revised January 23, 2007

This paper presents a novel multiaxis positioner that operates on the magnetic-levitation (maglev) principle. This maglev stage is capable of positioning at the resolution of a few nanometers over a planar travel range of several millimeters. A novel actuation scheme was developed for the compact design of this stage that enables six-axis force generation with just three permanent magnets. We calculated the forces with electromagnetic analysis over the whole travel range and experimentally verified them with a unit actuator. The single-moving part, namely, the platen, is modeled as a pure mass due to the negligible effect of magnetic spring and damping. There are three laser interferometers and three capacitance sensors to sense the six-axis position/rotation of the platen. A lead-lag compensator was designed and implemented to control each axis. A nonlinear model of the force was developed by electromagnetic analysis, and input current linearization was applied to cancel the nonlinearity of the actuators over the extended travel range. Various experiments were conducted to test positioning and loading capabilities. The 0.267kg single-moving platen can carry and precisely position an additional payload of 2kg. Its potential applications include semiconductor manufacturing, microfabrication and assembly, nanoscale profiling, and nanoindentation.

Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

A photograph of the developed multiaxis maglev positioner

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Figure 2

Cross-sectional side view of the novel dual-axis unit actuator showing magnetic-field lines and directions of forces

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Figure 3

Top view of the vertical and horizontal coils in a dual-axis actuation system showing the directions of forces on each section of the coils

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Figure 4

Exploded view of the assembly of the maglev stage

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Figure 5

Instrumentation structure of the maglev stage

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Figure 6

Laser-interferometry setup of the maglev stage

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Figure 7

Allocation of the coordinate axes on the platen for modal force and displacement transformations. The positive directions of ψ, θ, and ϕ follow the right-hand convention.

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Figure 8

Position noise in (a) x and (b) z

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Figure 9

50nm step response in x

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Figure 10

1μm step response in the x axis with perturbed motions in the other five axes

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Figure 11

10μm consecutive steps in x

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Figure 12

(a) 5mm ramp motion in x and (b) position error in x in this motion

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Figure 13

500μm radius circular motion in the x-y plane

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Figure 14

Path in a shape of a spur gear of 500nm inner radius and 675nm outer radius in the x-y plane

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Figure 15

The logo of Texas A&M University plotted over an area of 80×60μm2 in the x-y plane

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