Six-axis position measurement system for levitated motion stages

Conventional multi-axis motion measurements are achieved by using single-axis position sensors through serial or parallel kinematic chains, and therefore are susceptible to bearing error motion and structural deformation caused by thermal and mechanical loads. This paper presents a stereo camera-based position measurement system that can directly measure the relative position between two rigid bodies in 6 degrees-of-freedom. Experiments on a magnetically levitated motion stage have demonstrated sub-micron resolution, 16 μm uncertainty, and 8000 Hz sampling rate in a measurement volume of 400 mm × 400 mm × 15 mm.