Dual-Tendon Routing: Tendon Routing for Under-Actuated Tendon-Driven Soft Hand-Wearable Robot

Abstract

The under-actuated tendon-driven mechanism enables the development of light and compact hand-wearable robots by allowing the robots to assist in adaptive motions. However, tendon friction and elongation accumulate as the tendon passes through many joints, causing hysteresis and detrimental effects on tension distribution, reliability, and efficiency. To mitigate these issues, we present a Dual-Tendon routing (DTR) method and a novel approach to generate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$2^{n+1}-1$</tex-math></inline-formula> DTRs for robots that actuate <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$n$</tex-math></inline-formula> fingers. This letter also introduces five performance factors—adaptability, torsional balance, reliability, efficiency, and transmission ratio—that can be used to find the optimal routings among derived DTRs. The effectiveness of our proposed framework is demonstrated through its application to the Exo-Glove, a soft hand-wearable robot. The reduced friction at the flexion tendon improves under-actuation performance, reduces hysteresis at the flexor, and allows the active extensor to be replaced with a passive tendon. The changed tendon routing also enables the tension sensor to be located at the wearing part in a compact size.