Design and Modeling of Tetrahedral Soft-Legged Robot for Multigait Locomotion

Abstract

This article presents a novel tetrahedral soft-legged robot for multigait locomotion, including steering, crawling, and rolling along three different directions. The proposed robot has a compact structure with four active soft legs plugged together onto a rigid pivot. Each active soft leg is made of a novel pneumatic omnidirectional bending soft actuator. Locomotion is achieved by the sequential bending actuation of soft legs. Different inflation sequences are used to drive the soft legs to bend and realize multigait locomotion. Multiple gaits are analyzed with dynamic simulation methods. By discretizing the continuous soft leg into rigid links hinged end-to-end, a multibody dynamics model is built to simulate the robot dynamics and verify the feasibility of multigait locomotion. The crawling speed can reach 3.7 mm· <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{s}^{-1}$</tex-math></inline-formula> , the steering speed can reach 1.1 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ \text{s}^{-1}$</tex-math></inline-formula> , and the rolling speed can reach 5.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ \text{s}^{-1}$</tex-math></inline-formula> and 20.6 mm· <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{s}^{-1}$</tex-math></inline-formula> . Experimental and simulation results show the capability of multigait locomotion of the proposed robot. The proposed robot has potential applications in search and rescue.