Eversible duoprism mechanism

Abstract

In this study, a novel duoprism mechanism that demonstrates a fascinating eversion motion is developed. The mechanism comprises three scalable platforms and nine retractable limbs and is constructed by inserting prismatic and revolute joints into the edges and vertices of the duoprism, respectively. According to mobility and kinematic analyses, the mechanism has five degrees of freedom. Six inputs, including a redundant one, are required to overcome singularity and achieve an eversion motion. In the eversion motion, three platforms expand/contract synchronously, and the mechanism continuously turns inside out. The detailed gaits of eversion motion along an ellipse and a circle after a cycle are illustrated with two examples. A kinematic simulation is conducted, and a manual prototype is fabricated to verify the feasibility of the eversible duoprism mechanism.

Key words： duoprism; eversion motion; singularity; over-constrained

Acknowledgements

The authors thank Prof. Jian S Dai (Centre for Robotics Research, King’s College London) for suggesting the term “eversible duoprism mechanism”. The authors are also grateful to Dr. Xianwen Kong of Heriot-Watt University for his valuable discussions. This study was supported by the National “Climbing” Program of China (Grant No. 2015BAK04B02).

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