A Long-Stroke Nanopositioning Stage With Annular Flexure Guides

This article presents a long-stroke nanopositioning stage supported with annular flexure guides to be used in high-precision optical instruments. First, the structure of the novel annular flexure guide and the positioning stage is proposed. Because of the symmetric configuration of the flexure guide, large motion range, high linearity, and high stiffness ratio of the positioning stage are achieved. Second, the stiffness of the flexure guide is modeled by applying the two-port mechanical network method combining with the Castigliano's theorem and the static equilibrium equation of the structure. Afterwards, the dimension parameters of the flexure guide are optimized by applying the stiffness model to maximize the motion stiffness and the stiffness ratio of the positioning stage. Model validation and performance evaluation are conducted via finite element analysis. Finally, a prototype of the nanopositioning stage is fabricated, and the classical feedforward proportional integral derivative (PID) controller is employed to improve its motion accuracy. Experimental results show that the proposed positioning stage can achieve $\pm$ 5 mm motion range, 20 nm motion resolution, 20 nm positioning accuracy at the maximum output position, and micron tracking accuracy for both sinusoidal trajectory and triangular trajectory under the closed-loop controller.