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Autonomous docking based on optical positioning system for remotely operated vehicle
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Vågkraft)ORCID iD: 0000-0002-9840-2926
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Underwater docking is of high interest as it could be used to chargeunderwater robots while on a mission, thus extending their range of ac-tion, or to upload data without retrieving the vehicle, thus increasing itsmemory capacity. In this paper, the purpose of the docking system is toperform cable connections using remotely operated vehicles. The modelof an autopilot for autonomous docking is presented and the performancesof its components are analysed. This autopilot is based on measurementsfrom an optical positioning system which localizes the vehicle based onfeature detection from image processing. It shows that this positioning system could be integrated to the modelled autopilot and used in closed-loop for autonomous docking.

Keywords [en]
Optical positioning; closed-loop; Image processing; Remotely operated vehicle; Autonomous docking.
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:uu:diva-356562OAI: oai:DiVA.org:uu-356562DiVA, id: diva2:1236199
Available from: 2018-08-01 Created: 2018-08-01 Last updated: 2018-08-01
In thesis
1. Automation of underwater operations on wave energy converters using remotely operated vehicles
Open this publication in new window or tab >>Automation of underwater operations on wave energy converters using remotely operated vehicles
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the last fifteen years, the Division of Electricity at Uppsala University has been developing a wave energy converter (WEC) concept. The concept is based on a point-absorbing buoy with a directly driven linear generator placed on the seabed. Several units are connected to a marine substation, whose role is to collect and smooth the power absorbed from the waves and then bring it to the shore through one single cable.

A big challenge in the project is to reduce the costs related to the deployment and maintenance of the WECs and substation. Currently, those operations are performed by divers, which is costly and entail considerable risks. A possibility is to replace divers with automated solutions using small robots called remotely operated vehicles (ROVs). This PhD thesis proposes and analyses a method for deployment and maintenance of underwater devices with no use of diving operations.

Existing ROVs need additional modules and equipment in order to carry out operations with the required force and precision. Typical missions are inspection, shackles or slings removal, valve closing, and cable connection. The latter demands especially high precision in the positioning: 5 mm in distance and 5◦ in heading angle. In addition, this operation involves forces up to 200 N. This combination power-precision is not reached by existing ROVs. This PhD thesis presents a positioning system for underwater robot to enable autonomous positioning of the vehicle before cable connection.

The positioning system is composed of two green lasers and a monocular camera, and is based on image processing. Experimental results from laboratory testing show that the mean absolute error in distance measurement is as low as 6 mm at 0.7 m from the target, whereas the heading is minimized to 2◦. The computational time for the image processing is 13.6 ms per image, meaning the possibility of a 30 Hz measurement system. Used together with a closed-loop path-following unit, this positioning system can support autonomous docking. This PhD thesis presents the model of an autopilot and results from docking simulations, showing the performance of the positioning system used in closed-loop.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 74
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1695
Keywords
Remotely Operated Vehicles, wave energy, WEC deployment, cable connection, optical positioning system, autonomous underwater docking
National Category
Electrical Engineering, Electronic Engineering, Information Engineering Marine Engineering Ocean and River Engineering Energy Systems
Identifiers
urn:nbn:se:uu:diva-356565 (URN)978-91-513-0388-8 (ISBN)
Public defence
2018-09-21, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-08-22 Created: 2018-08-01 Last updated: 2018-08-28

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