Stereo Vision System for Vision-Based Control of Inspection-Class ROVs

Stanisław Hożyń,Bogdan Żak

doi:10.3390/rs13245075

Abstract

The inspection-class Remotely Operated Vehicles (ROVs) are crucial in underwater inspections. Their prime function is to allow the replacing of humans during risky subaquatic operations. These vehicles gather videos from underwater scenes that are sent online to a human operator who provides control. Furthermore, these videos are used for analysis. This demands an RGB camera operating at a close distance to the observed objects. Thus, to obtain a detailed depiction, the vehicle should move with a constant speed and a measured distance from the bottom. As very few inspection-class ROVs possess navigation systems that facilitate these requirements, this study had the objective of designing a vision-based control method to compensate for this limitation. To this end, a stereo vision system and image-feature matching and tracking techniques were employed. As these tasks are challenging in the underwater environment, we carried out analyses aimed at finding fast and reliable image-processing techniques. The analyses, through a sequence of experiments designed to test effectiveness, were carried out in a swimming pool using a VideoRay Pro 4 vehicle. The results indicate that the method under consideration enables automatic control of the vehicle, given that the image features are present in stereo-pair images as well as in consecutive frames captured by the left camera.

Highlights

Vision-based control of underwater vehicles enables autonomous operations
Missions, we decided that the control system would be tested in a swimming pool. This solution was convenient because it allowed for a precise measurement of the displacement of an Remotely Operated Vehicles (ROVs), which would be very challenging in the real environment
RGB cameras are a viable option for Visual Odometry, Visual Simultaneous

Summary

Introduction

Vision-based control of underwater vehicles enables autonomous operations. It facilitates complex missions, including surveillance of pipelines [1], inspection of cables [2], docking of vehicles [3], deep-sea exploration [4], and ship hull inspection [5]. These tasks require continuous visual feedback obtained from either monocular or stereo vision systems [6]. In order to improve performance, the vision system is often supported by acoustic and inertial sensors [7]. The most common collaborating devices for this purpose are [8]: the Doppler Velocity Log (DVL); the Inertial

Objectives

Methods

Results

Conclusion