Two-Phase Lorentz Coils and Linear Halbach Array for Multiaxis Precision-Positioning Stages With Magnetic Levitation
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1996-2012 IEEE. 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 $ ext{14.3}{, ext{cm}} imes ext{14.3}{, ext{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 $ ext{0.1},mu { ext{rad}}$, which is a record in the literature. The maximum travel range in $XY$ with laser interferometers is ${ ext{56}, ext{mm}} imes ext{35},{ ext{mm}}$, 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.
