The Quadruped Soft Tail: Compliant Grasping and Swabbing for Contamination Surveys in Harsh Environments

2026-06-29

AI Summary

This work addresses the challenge of safely and efficiently performing beryllium contamination sampling in highly radioactive, cable-cluttered environments where conventional robots struggle. The authors propose a novel quadrupedal robotic system that integrates, for the first time, a lightweight, compliant tendon-driven soft tail combined with a hollow flexible backbone and soft grippers to automate the entire sampling workflow—including tissue extraction, surface swabbing, and sample deposition. By replacing rigid manipulators with a soft tail, the design synergistically combines legged locomotion with compliant manipulation, enabling operation in confined and hazardous spaces. The system employs a closed-chain kinematic model and a singularity-robust task-space controller to support intuitive teleoperation. Experiments demonstrate negligible influence of gripper actuation on body deformation, effective stiffness and pretension modulation via common-mode tendon actuation, and successful completion of a fully autonomous contamination sampling sequence without human intervention.

Abstract

Beryllium contamination surveys in radioactive areas are challenging for robots in environments cluttered with cables and electronics. To address this problem, we have developed a novel quadruped system augmentation: A lightweight, soft, and compliant tendon-actuated robotic tail mounted on a quadruped robot. The tail features a hollow, flexible backbone and a tendon-actuated soft gripper that enables the robot to pick up sampling tissues, swab contaminated surfaces, and release the tissues at designated collection locations for subsequent beryllium analysis. To enable intuitive teleoperation, a closed-form kinematic model and a singularity-robust task-space controller are developed. Experimental results demonstrate that gripper actuation has a negligible effect on robot shape, while common-mode tendon actuation provides an effective mechanism for stiffness modulation and preload control. Furthermore, experimental validation indicates that the proposed kinematic model provides a suitable basis for real-time task-space control. The proposed system combines the agility of legged locomotion with the compliance of soft robotic manipulation, enabling the complete contamination-survey procedure to be performed without human exposure. While motivated by beryllium contamination surveys at CERN, the proposed quadruped soft-tail concept is broadly applicable to legged robots operating in cluttered, confined, or hazardous environments where conventional rigid-link manipulators are undesirable.

Problem

• beryllium contamination
• quadruped robot
• soft robotic manipulation
• hazardous environments
• compliant grasping

Innovation

• soft robotic tail
• tendon-actuated gripper
• compliant manipulation
• quadruped robot
• task-space control