Superelastic Tendon-Like Bowden Cables: Advancing Assistive Exoskeletons
Gregorio Pisaneschi, José M. Catalán, Andrea Blanco, Nicola Sancisi, Nicolas Garcia-Aracil, Andrea Zucchelli
AI summary
Problem
Conventional tendon-driven Bowden cables in assistive exoskeletons suffer from high friction, inefficient force transmission, mechanical wear, and safety risks due to rigidity, limiting their effectiveness for users with severe disabilities.
Approach
The authors developed and tested a Bowden cable system using a single superelastic Nitinol wire inside a PTFE sheath, evaluating its mechanical efficiency, durability, and electrical resistance-based self-sensing capabilities under simulated exoskeleton operating conditions.
Key results
- 75% lower friction and nearly double the transmission efficiency compared to stainless steel cables
- Accurate overload detection via electrical resistance monitoring with less than 1% force error
- Inherent passive force self-limiting behavior mimics biological tendon protection during collisions
- Successful integration into a hand-assistive exoskeleton prototype enabling improved gripping performance
Why it matters
This biomimetic transmission design significantly enhances the safety, efficiency, and wearability of assistive exoskeletons, advancing human-robot interaction for rehabilitation and daily living support.
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 effi- ciency 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 ef- ficiencyofSEwires,with1/4thefrictionofconventionalsteelcables. In addition, a validated force-sensing capability, achieved by mon- itoring 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.