Development of a levitated tip/tilt scanning platform

Abstract

Levitation platforms, mostly in the form of planar motor designs, are widely spread across different industry sectors and even used in public transport. Their simple mechanical design enables high system performance in terms of motion range and positioning bandwidth, without friction-losses or the use of lubricants. The absence of a mechanical linkage between stationary and moving parts, particularly enables the attenuation of surrounding environmental vibrations. A common property of most levitation stages used for positioning is the aim for large translational ranges, with the actuation of the rotational degrees of freedom (DoFs) being only a necessary side effect, needed for stabilization. This is the cause for mostly low rotational motion ranges implemented in levitation platforms. In order to bring the benefits of levitation to other application possibilities, the aim of this thesis is the development of a levitated platform tailored for dynamic and large range operation in the rotational DoFs. To obtain system specifications, a literature review is carried out and realized systems are investigated. After the mechatronic design, a magnetically levitated platform prototype with an integrated optical sensor system is built. The passive mover carries a special magnet configuration - called halbach-array - for generation of the involved forces together with eight stator coils. By implementation of a single-input single-output (SISO) feedback control structure, the system is stabilized in a desired operation point and system dynamics are identified. By in-depth analysis of specific levitation system properties, various experiments and following control parameter tuning, a rotational range of ±1° is achieved in both axes. Additionally, the opportunity for translational motion is established at a possible travel range of ±0.2mm lateral and 0.25-1mm vertical. The tracking performance of the system is investigated by the use of rasterand Lissajous-trajectories, whilst a closed-loop positioning bandwidth of 100 Hz is achieved.