Distal-Stable Beam for Continuum Robots

TL;DR

This paper introduces the Distal-Stable Beam, a geometric design for continuum robots that significantly enhances distal stiffness while maintaining compliance, enabling safer and more precise operation.

Contribution

The paper presents a novel geometric primitive that achieves high distal stiffness in continuum robots without active control, improving safety and precision.

Findings

Distal stiffness is 12 times higher than at the center.

Approximately 100-fold improvement over conventional beams.

Enables compliance and stability without active stiffness modulation.

Abstract

Continuum robots are well suited for constrained environments but suffer from low distal stiffness, resulting in large posture errors under external loads. In this paper, we propose a novel structural primitive, the Distal-Stable Beam, which achieves a strong stiffness gradient through purely geometric design, maintaining compliance in the intermediate section while ensuring high distal rigidity. The structure consists of two parallel rods and one convergent rod constrained by guide disks, introducing geometric coupling that suppresses deformation modes and preserves distal posture. Experiments show that the distal stiffness is 12 times higher than at the center, corresponding to an approximately 100-fold improvement over a conventional cantilever beam. The proposed mechanism enables simultaneous compliance and distal stability without active stiffness modulation, providing a new design approach for continuum robots requiring both safety and precision.