Superelastic Tendon-Like Bowden Cables: Advancing Assistive Exoskeletons

Abstract

This study introduces a novel Bowden cable (BC) system for hand-assistive exoskeletons employing superelastic (SE) shape memory alloy wires to address key limitations such as efficiency and safety limitations. The unique properties of SE wires enable a single-wire transmission, offering enhanced performance, plus inherent self-sensing and self-limiting capabilities that provide tendon-like overload protection. Experimental results obtained with a setup simulating use conditions demonstrate the superior efficiency of SE wires, with 1/4 the friction of conventional steel cables. In addition, a validated force-sensing capability, achieved by monitoring electrical resistance, proves to accurately detect overloads within 1% force error. This, along with the inherent passive force self-limiting behaviour during simulated collisions, demonstrates the ability of the SE BC to effectively mimic the protective function of biological tendons. Therefore, this biomimetic innovation in soft robotic transmission significantly improves safety and efficiency, presenting a promising advancement for human-robot interaction in assistive and rehabilitative robotics.