Insect-Tarsus-Inspired Legs: Toward Improvement of Gripping Ability of Small Tree-Climbing Robots

Abstract

This study proposes an insect-tarsus-inspired leg for a small tree-climbing robot. The expansion of the range of the grippable diameter is a concern for small tree-climbing robots; in this study, we focus on the leg structure of insects that can grip trees of various diameters and reproduce it. The shape memory alloy actuator and superelastic alloy sheet are used to reproduce the bending and extension of the insect tarsus, which is important for gripping. The developed robot with four insect-tarsus-inspired legs exhibits excellent gripping ability in a cylinder gripping experiment: the range of grippable diameter is 40–250 mm, and the gripping force is 1 N or more. This robot weighs 5.8 g with dimensions of W55 x L60 x H55 mm, and is compact and lightweight; it can exert a gripping force 17 times its own weight over a wide range of diameters. A similar gripping force is confirmed when the Kitayama cedar is gripped. This weight-to-payload ratio is significantly larger than that of conventional tree-climbing robots. This indicates that insect-tarsus-inspired legs can contribute to improving the gripping ability of small tree-climbing robots.