Hybrid ROV/AUV underwater robotic system for safe and robust remote operations

Abstract

Over the past years, the class of Hybrid Remotely Operated Vehicles (HROVs) has emerged as a groundbreaking innovation in marine robotics, by combining the advantages of Autonomous Underwater Vehicle (AUV) and Remotely Operated Vehicle (ROV) technologies. These vehicles are designed for deep-sea exploration and intervention, capable of transitioning between different operational modes to perform a variety of underwater tasks within a single cruise deployment. This work focuses on the development of a highly versatile HROV with four distinct operational modes, determined by the level of autonomy and the presence or absence of the cable. A virtual tether was established through the use of acoustic modems for communication, along with the implementation of a wireless communication protocol. Given the bandwidth constraints, image compression techniques were applied to Forward-Looking Sonar (FLS) and camera images. To enhance safety, an intelligent on-board system was devised by triggering emergency systems due to potential collisions with obstacles or substantial tether cable forces, offering mode transitions as a responsive solution. This dissertation also presents an innovative obstacle avoidance method, which combines BK-Product of fuzzy relations and potential field techniques. Additionally, a cable model has been implemented to simulate the forces exerted on the vehicle, with emergency system activating when cable forces exceed the predefined threshold. The simulation results underscore the practicality of mode transitions across various scenarios and their substantial contribution to enhancing vehicle safety.