Flexure-Based Magnetically Levitated Dual-Stage System for High-Bandwidth Positioning

Bandwidth is a critical specification for motion positioning systems because fast response to reference and broad-band disturbance rejection is highly desirable in industrial applications, e.g., two-dimensional (2-D)/3-D scanning. This paper presents a parallel-actuation, dual-stage concept to enhance the bandwidth of magnetically levitated (maglev) positioning system, which is realized by utilizing compliant joints to construct a monolithic-cut flexure-based fine positioning stage within the primary maglev stage, hence turning such a dual-stage system into a fully cable-less maglev system. An integrated design approach is employed to design the flexure-based secondary stage by optimizing both the mechanical parameters and the controller parameters, where various specifications, e.g., stability, performance, and saturation, are considered under the proposed framework. Experimental results have shown that the prototype can achieve a rootmean- square error of 43 nm in the principal axis even though the accuracy of the primary maglev stage is limited in micron-level because of the noise of capacitive sensors. Results also show that the developed prototype can significantly improve the closed-loop bandwidth of the maglev system from 20 to around 200 Hz.