A New Decoupling Method for Cable-Driven Joints Based on an Anti-Parallelogram Mechanism
Seungcheol Oh, Seungbum Lim, Jungwook Suh
AI summary
Problem
Cable-driven manipulators suffer from kinematic coupling when routing cables through proximal links, while existing decoupling solutions rely on fragile rolling contacts or high-friction external cables that compromise precision and reliability.
Approach
The design routes drive cables directly through the joint interior using an anti-parallelogram mechanism and optimized internal idlers to maintain a nearly constant cable path length during rotation, mechanically isolating distal joints.
Key results
- Cable path length variation minimized to 2.14 μm via idler optimization
- Distal joint interference reduced to 0.0815° RMSE during actuation
- End-effector positional repeatability achieved with sub-millimeter error (max 0.2786 mm RMSE)
- Functional 2-DOF prototype successfully validated decoupling and tracking performance
Why it matters
Enables safe, agile, and lightweight cable-driven robots for human-robot interaction by providing a robust, high-precision decoupling solution free from backlash and high-friction external routing.
Abstract
This paper proposes a novel anti-parallelogram mechanism (APM)-based cable-driven joint that achieves both the kinematic decoupling characteristic of rolling joints and the surface-contact robustness of link structures. Through the optimization of internal idlers, the cable path length remains nearly constant without complex gears or ligaments. Experimental validation using a 2-DOF prototype demonstrated negligible distal joint interference (0.0815◦ RMSE) during actuation. Furthermore, the system exhibited sub-millimeter positional repeatability (maximum RMSE of 0.2786 mm), establishing the proposed design as a robust, high-precision decoupling solution.