Planar Magnetic Drives and Bearings for Multi-Axis Nanopositioning Machines with Large Travel Ranges

Future semiconductor industry or biotechnology applications require positioning systems guaranteeing repeatability and uncertainty in the nanometre range together with planar (x-y-coordinates) travel ranges in the order of several 100 mm. We contribute in this research by investigating planar magnetic drives combined with air bearings or planar magnetic bearings for nanopositioning- and nanomeasuring machines (NPM/NMM). The paper gives an overview on the design, the dimensioning and the arrangement of these magnetic drives and bearings. A planar motor concept for travel ranges up to 250 mm comprising planar magnetic drives together with air bearings is presented first. Based on the design of the drive units the central ideas of the concept are presented. The results and improvements of our research obtained on different test setups are exemplary illustrated using this motor concept. Second planar magnetic bearings are investigated. They exhibit well-known non-linear effects like hysteresis, saturation or eddy-current losses. Parametric identification approaches are applied for a model-based description of the system behaviour. Non-linear control concepts and signal filtering methods are investigated to enhance the system dynamics and reduce the positioning noise. In a linear test rig for a single magnetic bearing, positioning noise with a standard deviation of less than 5 nm has been achieved.