Two-Phase Lorentz Coils and Linear Halbach Array for Multiaxis Precision-Positioning Stages With Magnetic Levitation

Abstract

In this paper, a new framework for linear permanent-magnet (PM) machines with applications in precision motion control is proposed and validated. A single forcer generating two independent force components in two perpendicular directions is the fundamental unit of the framework. Each forcer consists of two planar Lorentz coils separated by a 90° or 270° phase difference and parallel to a Halbach magnet array. Many coil pairs can be assembled to the same platen to move over a common magnet matrix, forming a linear or planar PM motor. Advantages of this framework include a linear system model, the capability to magnetically levitate the mover in multiaxis stages, and that to generate long translational motion range. The framework developed herein is validated by a six-degree-of-freedom magnetically levitated (maglev) stage. The dimension of the moving platen's frame is 14.3 cm × 14.3 cm, and its total mass is 0.75 kg. The achieved positioning resolution in translations along X, Y , and Z is 10 nm. The positioning resolution in out-of-plane rotation is 0.1 μrad, which is a record in the literature. The maximum travel range in XY with laser interferometers is 56 mm × 35 mm, limited by the size of the precision mirrors. With the coils' total mass of only 0.205 kg, the achieved acceleration is 1.2 m/s <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Experimental results exhibit reduced perturbations in other axes of in-plane motions.