ORIGINAL RESEARCH article
Front. Robot. AI
Sec. Robot Design
Volume 12 - 2025 | doi: 10.3389/frobt.2025.1627116
This article is part of the Research TopicAdvances and Challenges in Mobile Robot Design and Control for Diverse EnvironmentsView all articles
A Pivot Joint Steering Mechanism for Tip-Everting Soft Growing Robots
Provisionally accepted
- The University of Sheffield, Sheffield, United Kingdom
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Soft growing robots (SGRs) navigate confined environments by everting material from the tip while keeping the rest of the body stationary, enabling frictionless navigation. This opens up huge potential for inspection, search, and rescue tasks. However, controlling the direction of tip growth is still a challenge because of the ever-changing tip of the robot during tip growth. This study presents a compact steering mechanism that integrates a tendon-driven pivot joint with a pressure-tunable internal bladder. By modulating friction between the pivot joint and the inner material, the mechanism switches between two states: decoupled (stationary for bending) and coupled (move forward together with robot's inner material). This enables the robot to bend locally and then continue growing in the new direction, without using complex full-body actuation or external mechanisms. A robotic platform was developed to implement this mechanism, and its performance was characterized and validated through modeling and experiments. Experimental results confirm that the mechanism achieves reliable tip steering, closely matches kinematics models, and interacts gently with the environment. The proposed design offers a scalable and structurally simple solution for long-range navigation in soft growing robots.
Keywords: Soft growing robot, Actuation mechanism design, Tendon actuated, confined space navigation, Soft robot
Received: 12 May 2025; Accepted: 04 Jul 2025.
Copyright: © 2025 Ji, Bi and Cao. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Lin Cao, The University of Sheffield, Sheffield, United Kingdom
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