Autonomous Underwater System for Targeted Assessment and Repair

The AQUASTAR project seeks to developed technology that enables localization and repair of holes in aquaculture net pens. This involves the use of unmanned underwater vehicles and R&D on systems for automatic hole detection, hole repair tools and control systems for the vehicle and a robot manipulator. This also includes a system that allows the vehicle and manipulator to collaborate, where the quick response and the precision of the manipulator motions will be used to compensate for the slow and unwanted behavior of the vehicle due to, e.g., disturbances such as currents or imprecise control. Moreover, the technology that the project aims to develop will be applicable for other marine operations as well. Examples include, e.g., grasping objects in the water column or on the seafloor, operations on subsea installations, maintenance operations on floating wind farms, and both damage detection and repair on ship hulls. The envisioned R&D in the project addresses five different but interconnected goals: a) structure and object relative navigation; b) optical object detection; c) vehicle-manipulator system control; d) repair tools for holes in aquaculture net pens; and e) validation of the fully integrated system through field trials. The project will make use of the interdisciplinary competence, industry expertise and experiences (Njord Aqua, SINTEF Ocean, Måsøval, NTNU) with the overarching goal of developing and demonstrating a tool that contributes to immediate repair of holes during net inspection operations. The results from the project includes new systems that facilitate less fish escapes in sea-based aquaculture and advance sustainability by reducing the environmental footprint in the aquaculture industry. These results will be applicable within other maritime industries, such as fisheries, subsea oil and gas, offshore wind and shipping.

In Norway, the main reason for fish escape in sea-based fish cages is due to holes in the net. Fish escape has a negative impact on the environment through mixed breeding and spreading of pathogens to wild fish and on production through loss of invested resources. It is common practice to employ remotely operated vehicles (ROVs) for net inspection, but it is challenging to accurately control the ROV while coping with environmental forces and avoid causing damage to the net. The task increases in complexity when the operator is also required to carefully look for holes and keep track of already inspected areas. Holes are typically repaired by divers who sew the net, but the duration between detection and repair can be long, and the repair operations involve both high personal risks and costs. Attempts have been made to repair holes using underwater vehicles and customized solutions but none of these are known to be widely applied. The AQUASTAR project will develop innovative technology for autonomous structure inspection, feature localization and structure repair, where aquaculture is chosen as a case study. The R&D challenges thus relate to net- and hole-relative positioning, hole localization, coupled vehicle-manipulator control for conducting repair operations, and hole repair tools. Solutions to these challenges may be considered enabling technologies for further research and innovations in other maritime industries where robotic systems are required to perform inspection, maintenance, and repair operations. The AQUASTAR project aims to reduce the number of fish escapes and at the same time improve the underwater robotic inspection, maintenance, and repair services in aquaculture.