Parameter identification for nanopositioning of a 6-axis maglev stage with moving Lorentz coils

摘要

This paper presents the design, parameter identification, and control of a 6-axis magnetically-levitated (maglev) nanopositioning stage with the xy travel ranges on the order of centimeters. The maglev stage has a moving frame with Lorentz coils and a stationary Halbach magnet matrix. A new method to identify the dynamic models is developed and verified experimentally. The dimension and the mass of the moving platen are 14.3 cm × 14.3 cm and 0.75 kg, respectively. With the multi-input-multi-output system decoupled into six single-input-single-output (SISO) systems, proportional-integral-derivative (PID) controllers are designed and tested on the 6-axis maglev stage. The achieved positioning resolutions are 10 nm in x, y, and z, 0.1 μrad in out-of-plane rotations, and 1 μrad in the rotation about the vertical axis. The achieved acceleration in the horizontal plane is 0.6 m/s2. With laser interferometers, the maximum travel range of the stage is 35 mm χ 56 mm, limited by the lengths of the precision mirrors.