Design Optimization of Three-Dimensional Wire Arrangement Considering Wire Crossings for Tendon-driven Robots

TL;DR

This paper presents a novel 3D wire arrangement optimization method for tendon-driven robots that considers wire crossings, improving design efficiency for complex structures beyond traditional 2D or simplified approaches.

Contribution

It introduces a multi-objective black-box optimization framework for 3D wire arrangements that prevents crossings and ensures torque requirements, addressing limitations of prior simplified models.

Findings

Optimized wire arrangements successfully prevent crossings in 3D structures.

The method ensures sufficient joint torque along target trajectories.

Demonstrated effectiveness on various 3D link structures.

Abstract

Tendon-driven mechanisms are useful from the perspectives of variable stiffness, redundant actuation, and lightweight design, and they are widely used, particularly in hands, wrists, and waists of robots. The design of these wire arrangements has traditionally been done empirically, but it becomes extremely challenging when dealing with complex structures. Various studies have attempted to optimize wire arrangement, but many of them have oversimplified the problem by imposing conditions such as restricting movements to a 2D plane, keeping the moment arm constant, or neglecting wire crossings. Therefore, this study proposes a three-dimensional wire arrangement optimization that takes wire crossings into account. We explore wire arrangements through a multi-objective black-box optimization method that ensures wires do not cross while providing sufficient joint torque along a defined target trajectory. For a 3D link structure, we optimize the wire arrangement under various conditions, demonstrate its effectiveness, and discuss the obtained design solutions.