Novel electromagnetic actuation scheme for multiaxis nanopositioning

Abstract

In this paper, we present a novel electromagnetic actuation scheme for nanoscale positioning with a six-axis magnetic-levitation (Maglev) stage, whose position resolution is 3 nm over an extended travel range of 5x5 mm in the x-y plane. We describe the conceptualization of the actuation scheme, calculation of forces, and their experimental verification in detail. This actuation scheme enables the application of forces in two perpendicular directions on a moving permanent magnet using two stationary current-carrying coils. The magnetic flux generated by the magnet is shared by the two coils, one right below and another on one side of the magnet. The magnitudes and directions of the currents in the coils govern the forces acting on the magnet, following the Lorentz-force law. We analyzed and calculated the electromagnetic forces on the moving magnet over a large travel range. We used feedback linearization to eliminate the force-gap nonlinearity in actuation. The new actuation scheme makes the Maglev stage very simple to manufacture and assemble. Also, there is no mechanical constraint on the single moving platen to remove it from the assembly. There are only three NdFeB magnets used to generate the actuation forces in all six axes. This reduces the moving-part mass significantly, which leads to less power consumption and heat generation in the entire Maglev stage. We present experimental results to demonstrate the payload and precision-positioning capabilities of the Maglev nanopositioner under abruptly and continuously varying loads. The potential applications of this Maglev nanopositioner include microfabrication and assembly, semiconductor manufacturing, nanoscale profiling, and nanoindentation.