Controller design and implementation of six-degree-of-freedom magnetically levitated positioning system with high precision

Abstract

This paper presents the controller design and implementation of a high-precision six-degree-of-freedom (6-DOF) magnetically levitated (maglev) positioner. This high-precision positioning system consists of a novel concentrated-field magnet matrix and a triangular single moving part that carries three three-phase permanent-magnet planar-levitation-motor armatures. Since only a single levitated moving part, namely the platen, generates all required fine and coarse motions, this positioning system is reliable and potentially low-cost. The three planar levitation motors based on the Lorentz force law not only produce the vertical force to levitate the triangular platen but also control the platen's position and orientation in the horizontal plane. The main contribution of this paper is that all 6-DOF motions are solely controlled by magnetic forces without any other means to support the platen's weight against gravity, and the most suitable controller of the magnetic levitation system was designed and implemented. The platen can be regarded as a pure mass, and the spring and damping effects are neglected except for the vertical directions. Single-input single-output digital lead-lag controllers were designed and implemented on a digital signal processor. This 6-DOF fully magnetically levitated positioner has a total mass of 5.91 kg and exhibits a 120×120 mm maximum travel range. The position resolution of 20 nm and position noise of 10-nm root mean square are demonstrated. The positioner has sub-microradian angular resolution in about the x, y, and z-axes. A maximum velocity of 24.8 mm/s in y is achieved. This single-moving-part maglev positioner structure is highly suitable for semiconductor manufacturing applications such as wafer steppers. Several experimental motion profiles are presented to demonstrate the maglev stage's capability of accurately tracking any planar and three-dimensional paths.

Keywords

real-time digital control magnetic levitation nanoscale positioning 6-DOF positioning precision manufacturing

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References

Design and control of a 6-degree-of-freedom levitated positioner with high precision. PhD Thesis, Department of Mechanical Engineering, Texas A&M University, College Station, Texas, May 2005.

Kim

W.-J.

Extended-range 6-DOF high-precision positioner for wafer processing. IEEE/ASME Trans. Mechatronics, 2006, 11(6), 682–689.

van Engelen

Bouwer

A. G.

Two-step positioning device using Lorentz forces and a static gas bearing, 1992, US patent number 5120034.

Sakino

Osanai

Negishi

Horikoshi

Inoue

Ono

Movement guiding mechanism, 1999, US patent number 5040431.

Wittekoek

Bouwer

A. G.

Displacement device, particularly for the photolithographic treament of a substrate, 1987, US patent number 4655594.

Salapaka

Sebastian

Design of high precision high bandwidth and reliable nanopositioning systems. In Proceedings of 2003 ASME International Mechanical Engineering Congress and Exposition, November 2003, paper 55554 (ASME, New York, NY, USA).

Feng

Seto

Tamura

Nonlinear vibration properties of a current-controlled attractive type maglev system. In Proceedings of 2003 ASME International Mechanical Engineering Congress and Exposition, November 2003, paper 41879 (ASME, New York, NY, USA).

Hinds

W. E.

Nocito

The Sawyer linear motor. In Proceedings of the Second Symposium on Incremental motion control systems and devices, Urbana, Illinois, 1973, pp. W1–W10 (University of Illinois, Urbana, USA).

Asakawa

Two dimensional positioning devices, 1986, US patent number 4626749.

10.

Asakawa

Two dimensional precise positioning devices for use in a semiconductor apparatus, 1985, US patent number 4535278.

11.

Pelta

E. R.

Two axis Sawyer motor for motion systems. IEEE Control Syst. Mag., 1987, 7, 20–24.

12.

Fujii

Kihara

Surface induction motor for two-dimensional drive. J. Inst. Elect. Engng Trans., 1998, 4, 221–228.

13.

Chitayat

Two-axis motor with high density magnetic platen, 1998, US patent number 5777402.

14.

Pelta

E. R.

Two axis Sawyer motor. In Proceedings of the 12th Annual IEEE Industrial Electronics Society Conference, Urbana, Illinois, 1986, pp. 3–8 (IEEE, Piscataway, NJ, USA).

15.

Compter

Ir. J. C.

Electro-dynamic planar motor. Precision Engng, 2004, 28, 171–180.

16.

16 Normag, Northern magnetics linear motor technology Manual, 1998 (Baldor, Fort Smith, AR, USA).

17.

17 Megamation. http://www.megamation.com/hm_frame.htm, 2001.

18.

Trumper

D. L.

Kim

W.-J.

Williams

M. E.

Magnetic arrays, 1997, US patent number 5631618.

19.

Kim

W.-J.

High-precision planar magnetic levitation. PhD Thesis, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 1997.

20.

Kim

W.-J.

Bhat

Integrated multidimensional positioner for precision manufacturing. J. Engng Mf., 2004, 218(4), 431–442.

21.

Quirk

Serda

Semiconductor manufacturing technology, 2001 (Prentice-Hall, NJ, USA).