Concentric-Tube-Eccentric-Rod: a Continuum Actuator for Macro-/Micro-Scale Translational Actuation

This paper proposes a motion de-amplificationbased actuator design, which comprises coarse and fine-stages that respectively achieve macro and micro-scale linear actuation. The proposed de-amplification mechanism, which outputs micrometer-level translation from scaling down millimeter-level translation input, is a hybrid continuum mechanism formed by embedding a many-backbone continuum mechanism in a concentric tube mechanism. A simplified Cosserat-rod-based analytical model incorporating a lumped Coulomb friction model is derived to describe the micro-actuation input/output behavior. A prototype is fabricated and its micro-motion capabilities are characterized by experiments. The results demonstrate the actuator's micro-motion output possesses a travel stroke of 232.48 mu m, resolution of 0.216 mu m, repeatability of 1.92 mu m (standard deviation), and output compliance among 13.52 - 16.01 mu m/N. Besides, open-loop positioning tests show a steady state error of 1.67 mu m (mean). The actuator exhibits excellent performance and can be created from off-the-shelf components using conventional workshop tools.