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Thruster model for Observation Class Remotely Operated Vehicle
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity. (Vågkraft)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
(English)In: Ocean Engineering, ISSN 0029-8018, E-ISSN 1873-5258Article in journal (Refereed) Submitted
Abstract [en]

For any small company or research group in offshore renewable energy, the costs to invest into Remotely Operate Vehicles (ROVs) for offshore operations are highly significant. There is however a potential to adapt and equip Observation Class ROVs (OCROVs) in order to make them perform light tasks, such as cable connection. OpenROV is a small and light OCROV with open source software, making it easy to implement tools, such as an autopilot. In this paper a model of the autopilot is presented. To be tested, it needs a model of the thrusters of the OpenROV. Those thrusters are hence tested, modelled in Simulink, and the experimental results are compared to the Matlab model.

Keyword [en]
ROV; wave energy; thrusters; OpenROV; autopilot
National Category
Robotics Control Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering with specialization in Automatic Control
Identifiers
URN: urn:nbn:se:uu:diva-302640OAI: oai:DiVA.org:uu-302640DiVA: diva2:962996
Projects
Lysekil project
Available from: 2016-09-07 Created: 2016-09-07 Last updated: 2016-09-07
In thesis
1. Underwater Electrical Connections and Remotely Operated Vehicles
Open this publication in new window or tab >>Underwater Electrical Connections and Remotely Operated Vehicles
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Remotely Operated Vehicles (ROVs) are underwater robots that perform different kind of operations, from observation to heavier tasks like drilling, carrying and pulling cables, etc. Those ROVs are costly and require skilled personal to operate it as well as equipment for transportation and deployment (boats, cranes, etc.).

The division for electricity at Uppsala University, is 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 that is located on the seabed, whose role is to collect and smooth the power absorbed from the waves and then bring it to the shore through one single cable.

Cable connection is a big challenge in the project because the WEC concept is small and many units are necessary to create a rentable farm. Nowadays this operation is performed by divers but using Observation Class ROV (OCROV) could be an interesting alternative since they are affordable at lower costs and easier to operate. Cable connection is however a heavy task and requires force that an OCROV does not have. It will need a docking system from which the vehicle will take its force. It would then go to the station, dock itself to this support plate, grab the cables and connect them together. This procedure cannot be done by the ROV operator because it requires accurate displacement and quick adjustment of the robot’s behavior.

An autopilot was created in Matlab Simulink that consists of three units: the path following, the ROV, and the positioning unit. The first one uses the vehicle’s position and computes the speed and heading to be applied on the ROV in order to guide it on the desired path. The second one contains a controller that will adapt the thrust of each propeller to the force needed to reach the desired heading and speed from the path following unit. It also contains the model of the ROV that computes its position and speed. The last unit consists of a Kalman filter that estimates the ROV position and will be used in case of delay or failure in the communication with the positioning sensors.

The autopilot model is used with a positioning system that utilizes green lasers and image processing. Two green lasers are used as fixed points in each camera picture and from their distance on the image, the actual distance between the ROV and the docking platform can be computed. In addition, optical odometry is used. The idea behind is to estimate how the ROV is behaving by evaluating the changes between two pictures of the camera. Those two systems, laser and odometry, work together in order to get more accurate results.

The laser system has so far been tested in air. The distance measurements gave interesting results with an error inferior to 3%, and angle measurements gave less than 10% error for a distance of one meter. One advantage with the system is that it gets more accurate as the vehicle gets closer to the docking point.

In addition to the ROV project, a review study was conducted on the variability of wave energy compared with other resources such as tidal, solar, and wind power. An analysis of the different tools and models that are used to forecast the power generation of those sources was done. There is a need for collaboration between the different areas because the future will aggregate those different sources to the grid and requires a unification of the models and methods.

Place, publisher, year, edition, pages
Uppsala: Department of Engineering Sciences, 2016. 66 p.
Series
UURIE / Uppsala University, Department of Engineering Sciences, ISSN 0349-8352 ; 349-16L
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-302644 (URN)
Presentation
2016-09-30, 16:08 (English)
Opponent
Supervisors
Projects
Lysekil project
Available from: 2016-10-18 Created: 2016-09-07 Last updated: 2016-10-18Bibliographically approved

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