Low-Cost Underwater In-Pipe Centering and Inspection Using a Minimal-Sensing Robot

TL;DR

This paper introduces a minimal-sensing, computationally efficient underwater robot system that autonomously centers and inspects submerged pipes using only basic sensors, demonstrating successful navigation in challenging conditions.

Contribution

The work presents a novel minimal-sensing approach combining simple sensors and geometric modeling for autonomous in-pipe underwater inspection, eliminating the need for complex multi-sensor setups.

Findings

Successful pipe centering and traversal in experiments

Reliable wall detection in noisy, reverberant conditions

No reliance on external tracking or Doppler sensors

Abstract

Autonomous underwater inspection of submerged pipelines is challenging due to confined geometries, turbidity, and the scarcity of reliable localization cues. This paper presents a minimal-sensing strategy that enables a free-swimming underwater robot to center itself and traverse a flooded pipe of known radius using only an IMU, a pressure sensor, and two sonars: a downward-facing single-beam sonar and a rotating 360 degree sonar. We introduce a computationally efficient method for extracting range estimates from single-beam sonar intensity data, enabling reliable wall detection in noisy and reverberant conditions. A closed-form geometric model leverages the two sonar ranges to estimate the pipe center, and an adaptive, confidence-weighted proportional-derivative (PD) controller maintains alignment during traversal. The system requires no Doppler velocity log, external tracking, or complex multi-sensor arrays. Experiments in a submerged 46 cm-diameter pipe using a Blue Robotics BlueROV2 heavy remotely operated vehicle demonstrate stable centering and successful full-pipe traversal despite ambient flow and structural deformations. These results show that reliable in-pipe navigation and inspection can be achieved with a lightweight, computationally efficient sensing and processing architecture, advancing the practicality of autonomous underwater inspection in confined environments.