Swimming Robot Manipulators for Subsea IMR

The needs for subsea inspection, maintenance, and repair (IMR) are increasing due to ageing infrastructure, new infrastructure being installed at greater depths, increasing focus on subsea processing, and extensive requirements from operators and governments.

Installation support and IMR operations have traditionally been carried out using remotely operated vehicles (ROVs). Conventional ROVs are expensive to operate and they have a rather long mobilization time, due to their need for a surface support vessel and a trained crew. Smaller, more specialized, and autonomous vehicles could efficiently handle a large part of the subsea IMR tasks.

The Underwater Swimming Manipulator (USM) is a novel bio-inspired autonomous underwater vehicle (AUV) with the ability to perform inspection and light intervention tasks in narrow spaces in subsea infrastructure; areas which are hard to reach with conventional underwater vehicles.

A USM is essentially an underwater snake robot (USR) equipped with thrusters and/or propellers. A USR is a slender, articulated structure consisting of serially connected joint modules, with ability to swim like a biological eel. In other words, a USM is a crossover between a typical ROV/AUV and a USR.

Operators often detect small incidents or abnormalities subsea, which need further investigation. Most of them are insignificant. The short mobilization time of the USM may contribute to significant cost savings by quickly responding to such demands, and may even help prevent unnecessary shutdowns.

This project focuses on how to control the USM, both when transporting itself from point A to B and when operating as a floating robotic arm. The main goal of the project is to achieve the required accuracy and stability to perform visual inspections and non-contact measurements. The USM is modular and can contain as many links and joints as you need. This flexibility is an important property of the USM. Another aspect of the project is thus to investigate how to properly exploit this advantage.

Publications:

J. Sverdrup-Thygeson, E. Kelasidi, K. Y. Pettersen, and J. T. Gravdahl, "Modeling of underwater swimming manipulators," 2016, accepted for presentation at the 10th IFAC Conference on Control Applications in Marine Systems (CAMS)

J. Sverdrup-Thygeson, E. Kelasidi, K. Y. Pettersen, and J. T. Gravdahl, "A control framework for biologically inspired underwater swimming manipulators equipped with thrusters," 2016, accepted for presentation at the 10th IFAC Conference on Control Applications in Marine Systems (CAMS)