A Self-Assembling Extendable Tendon-Driven Continuum Robot With Variable Length

Abstract

Tendon-driven continuum robots offer enhanced dexterity for intricate tasks within confined spaces. Nevertheless, when exclusively relying on remote access points, the entire fixed-length robotic system must be precisely repositioned to insert the robotic structure. Conversely, existing methods incorporating extendability tend to introduce complex design requirements, often resulting in a larger spatial footprint. Here, we present a novel design featuring a self-assembling continuum robotic structure during extension process with variable section- and segment lengths. We investigate a compact actuator unit ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{240} \,\text{mm}\times \text{140} \, \text{mm} \times \text{145} \,\text{mm}$</tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{1.5} \,\text{kg}$</tex-math></inline-formula> ) assembling a robotic structure smaller than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$15.4 \,\text{mm}$</tex-math></inline-formula> in diameter, with a three-tendon configuration and two omnidirectional bendable segments, able to extend up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$240 \,\text{mm}$</tex-math></inline-formula> . A reliable assembly performance was found with repeatability errors below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2 \,\text{mm}$</tex-math></inline-formula> during extension, while workspace and dexterity of the continuum robot achieved a median error of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2.39 \,\text{mm}$</tex-math></inline-formula> for bending. Our scalable approach reaches state-of-the-art dexterity and workspace range, showing great potential to be used for existing and future tendon-driven robotic systems.