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 $\text{14.3}{\,\text{cm}}\times \text{14.3}{\,\text{cm}}$ , 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 $\text{0.1}\,\mu {\text{rad}}$ , which is a record in the literature. The maximum travel range in $XY$ with laser interferometers is ${\text{56}\,\text{mm}}\times \text{35}\,{\text{mm}}$ , 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/s2. Experimental results exhibit reduced perturbations in other axes of in-plane motions.