Abstract

AbstractWe present a seabed profile estimation and following method for close proximity inspection of 3D underwater structures using autonomous underwater vehicles (AUVs). The presented method is used to determine a path allowing the AUV to pass its sensors over all points of the target structure, which is known as coverage path planning. Our profile following method goes beyond traditional seabed following at a safe altitude and exploits hovering capabilities of recent AUV developments. A range sonar is used to incrementally construct a local probabilistic map representation of the environment and estimates of the local profile are obtained via linear regression. Two behavior-based controllers use these estimates to perform horizontal and vertical profile following. We build upon these tools to address coverage path planning for 3D underwater structures using a (potentially inaccurate) prior map and following cross-section profiles of the target structure. The feasibility of the proposed method is demonstrated using the GIRONA 500 AUV both in simulation using synthetic and real-world bathymetric data and in pool trials.

Highlights

  • Thanks to technology breakthroughs in the last two decades, surveys conducted by autonomous underwater vehicles (AUVs) have become a standard tool supporting many marine robotics applications, such as marine geology [1], [2], underwater archaeology [3], habitat monitoring [4] and mine countermeasures (MCM) [5]

  • AUVs provide high resolution data thanks to near-bottom surveys and require little human supervision compared to their ship- or remotely operated vehicle (ROV)-assisted counterparts, and at a lower cost

  • An angle of incidence parallel to the bottom normal is desired in applications requiring imaging. These concerns can be addressed in the context of coverage path planning, which is the task of planning a path that allows a robot to pass its sensors over all points in a target area while avoiding obstacles

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Summary

INTRODUCTION

Thanks to technology breakthroughs in the last two decades, surveys conducted by autonomous underwater vehicles (AUVs) have become a standard tool supporting many marine robotics applications, such as marine geology [1], [2], underwater archaeology [3], habitat monitoring [4] and mine countermeasures (MCM) [5]. An angle of incidence parallel to the bottom normal is desired in applications requiring imaging These concerns can be addressed in the context of coverage path planning, which is the task of planning a path that allows a robot to pass its sensors over all points in a target area while avoiding obstacles. A simple range-sensing sonar can be used to perceive the target structure in situ and reactively follow its profiles to achieve coverage Toward this aim, we propose in this work a profile estimation and following method able to provide close proximity, fine-scale coverage of underwater structures using a rangesensing sonar. To perform profile following using these estimates, behavior-based horizontal and vertical profile following controllers are provided These controllers exploit hovering capabilities of recent AUV developments and are able to maneuver the vehicle surveying the target structure in close proximity while avoiding collision. The feasibility of the proposed methods is demonstrated both in simulation and in pool trials using GIRONA 500, a hovering-capable AUV

RELATED WORK
PROFILE ESTIMATION
Local Mapping
Profile Estimation on Regions of Interest
PROFILE FOLLOWING
Horizontal Profile Following
Vertical Profile Following
Off-line Coverage Planning Phase
THE GIRONA 500 AUV
On-line Profile Following Phase
COLA2: GIRONA 500’s Control Architecture
RESULTS
Simulated Vertical Profile Following
In-Water Profile Following Trials
VIII. CONCLUSION
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