REACT: Real-time Entanglement-Aware Coverage Path Planning for Tethered Underwater Vehicles

2025-07-14

AI Summary

Tethered underwater robots frequently suffer from tether entanglement during inspection of complex submerged structures, compromising mission safety and completeness. Method: This paper proposes a real-time obstacle-avoidance coverage path planning framework. It innovatively integrates a signed distance field (SDF)-based environmental map with a geometry-aware, tension-constrained tether dynamics model to enable efficient, real-time tether state simulation. An online replanning mechanism—driven by a maximum allowable tether length constraint—is introduced to proactively mitigate entanglement risk. Contribution/Results: In pipeline inspection tasks, the method achieves 100% spatial coverage with zero physical entanglements. Simulation throughput improves by 20% over conventional approaches. In physical experiments, it is the only method to complete the full inspection task without entanglement-related failure. This work establishes a verifiable theoretical framework and practical technical pathway for safe, efficient, and complete coverage inspection using tethered underwater robots.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Planning, Routing, and Scheduling: Replanning and Plan Repair
• Humans and AI: Planning and Decision Support for Human-Machine Teams

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Graph Algorithms and Modeling for the Web: Efficient manipulation of static and dynamic Web-related graphs
• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics

Abstract

Inspection of complex underwater structures with tethered underwater vehicles is often hindered by the risk of tether entanglement. We propose REACT (real-time entanglement-aware coverage path planning for tethered underwater vehicles), a framework designed to overcome this limitation. REACT comprises a fast geometry-based tether model using the signed distance field (SDF) map for accurate, real-time simulation of taut tether configurations around arbitrary structures in 3D. This model enables an efficient online replanning strategy by enforcing a maximum tether length constraint, thereby actively preventing entanglement. By integrating REACT into a coverage path planning framework, we achieve safe and optimal inspection paths, previously challenging due to tether constraints. The complete REACT framework's efficacy is validated in a pipe inspection scenario, demonstrating safe, entanglement-free navigation and full-coverage inspection. Simulation results show that REACT achieves complete coverage while maintaining tether constraints and completing the total mission 20% faster than conventional planners, despite a longer inspection time due to proactive avoidance of entanglement that eliminates extensive post-mission disentanglement. Real-world experiments confirm these benefits, where REACT completes the full mission, while the baseline planner fails due to physical tether entanglement.

Problem

• Prevent tether entanglement in underwater vehicle inspections
• Enable real-time path planning with tether length constraints
• Achieve safe and optimal coverage despite tether limitations

Innovation

• Geometry-based tether model using SDF
• Online replanning with length constraint
• Safe optimal paths via REACT framework