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Industrial robot as main equipment for testing and production of Wave Energy Converters
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Electricity. (dana.salar@angstrom.uu.se)ORCID iD: 0000-0003-3028-4887
2025 (English)Doctoral thesis, comprehensive summary (Other academic)
Description
Abstract [en]

Since 2001, research and development on the conversion of ocean wave energy into electricity has been conducted at the Division of Electricity at Uppsala University. Different Wave Energy Converter (WEC) technologies has been developed, such as the point-absorber linear Uppsala University WEC (UU-WEC) and the Low-RPM Torque Converter WEC (LRTC-WEC). 

This thesis focuses primarily on the development of a robotized dry test rig, to facilitate assessment of different WEC technologies in house. An existing industrial six degrees of freedom robot system is used to emulate buoy movement on the sea surface, with regard to the impact of hydrodynamic forces in real time. Two different methods for integrating a hydrodynamic model to the robot controller are presented: the force control and the position control methods. Both methods are evaluated and validated across various regular and irregular wave climates, as well as for different theoretical buoy shapes.  

The secondary focus in this thesis is the development of robotized production methods for the UU-WEC. The surface mounting of Neodymium Iron Boron (Nd2Fe14B) magnets and the cutting of rubber discs are investigated, resulting in viable solutions that include development and validation of robot tooling and robot cell proposals. 

A smaller segment of the thesis examines the use of robotics in teaching a course for bachelor engineering students. At the outbreak of the COVID-19 pandemic a challenging task was imposed: a swift shift to online distant education. A major task was to replace physical lab exercises with video recordings, detailed instructions and simulated laboratory environments. The results indicated that the upgraded online education successfully meet the course objectives.

The final part of the thesis investigates the use of WECs for powering a desalination plant. Desalination presents a viable solution for islands or coastal regions deficient in freshwater resources, but is also an energy intensive process. Practical experiment evaluated the possibility of utilizing the UU-WEC as power source for desalination plants.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2025. , p. 78
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2485
Keywords [en]
Dry test rig, Industrial robotics, Manufacturing automation, Large-scale production, Linear generator, Wave energy converter, Engineering education, Desalination
National Category
Robotics and automation Other Electrical Engineering, Electronic Engineering, Information Engineering Communication Systems Control Engineering
Research subject
Engineering Science with specialization in Science of Electricity; Engineering Science with specialization in Electronics; Engineering science with specialization in Applied Mechanics; Engineering Science with specialization in industrial engineering and management; Electrical Engineering with specialization in Automatic Control; Engineering Science with specialization in industrial engineering and management
Identifiers
URN: urn:nbn:se:uu:diva-544285ISBN: 978-91-513-2337-4 (print)OAI: oai:DiVA.org:uu-544285DiVA, id: diva2:1920225
Public defence
2025-02-10, Polhem, Lägerhyddsvägen 1, 75237 Uppsala, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2025-01-17 Created: 2024-12-10 Last updated: 2025-02-05
List of papers
1. Preparing the Uppsala University wave energy converter generator for large-scale production
Open this publication in new window or tab >>Preparing the Uppsala University wave energy converter generator for large-scale production
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2014 (English)Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Halifax, Canada: , 2014
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-237554 (URN)
Conference
5th International Conference on Ocean Energy
Available from: 2014-12-03 Created: 2014-12-03 Last updated: 2024-12-10
2. Learnings from the rapid online transition of a real-world project task-based engineering course
Open this publication in new window or tab >>Learnings from the rapid online transition of a real-world project task-based engineering course
2022 (English)In: 2022 IEEE Frontiers in Education Conference (FIE), Institute of Electrical and Electronics Engineers (IEEE), 2022Conference paper, Published paper (Refereed)
Abstract [en]

This Innovative Practice Full Paper presents the results and learnings from a rapid and forced transition to online teaching of a campus-based and practical lab exercise intense course in robot engineering. Founded in previous pedagogical development work, we continued with activating and varied teaching methods connected through integrated project tasks. The online transition is evaluated from student course evaluations, examination results and the teachers’ experiences from ten campus course occasions and four online course occasions during ten years. The paper focuses specifically on the combination of an innovative online lecturing format and fully virtual robot lab exercises. Our aim is to present learnings of interest for the engineering education community. The results highlight a successful and appreciated online course transition, with possibly improved student learning. In particular the prerecorded video lectures were praised, the virtual labs was similarly appreciated as campus labs and it was demonstrated that online robot programming can be performed virtually, while practical lab exercises and study visits were still missed.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2022
Series
IEEE Frontiers in Education Conference, ISSN 1539-4565, E-ISSN 2377-634X
Keywords
engineering education, project organized learning, online teaching, virtual lab exercises, video lectures
National Category
Didactics Robotics and automation
Identifiers
urn:nbn:se:uu:diva-489940 (URN)10.1109/FIE56618.2022.9962454 (DOI)001204427600080 ()2-s2.0-85143810738 (Scopus ID)978-1-6654-6245-7 (ISBN)978-1-6654-6244-0 (ISBN)
Conference
IEEE Frontiers in Education Conference, FIE 2022, Uppsala, Sweden, October 8-11, 2022
Funder
Uppsala University
Available from: 2022-12-06 Created: 2022-12-06 Last updated: 2025-02-05Bibliographically approved
3. A robotized 6-DOF dry test rig for wave power
Open this publication in new window or tab >>A robotized 6-DOF dry test rig for wave power
2023 (English)In: Sustainable Energy Technologies and Assessments, ISSN 2213-1388, E-ISSN 2213-1396, Vol. 59, article id 103393Article in journal (Refereed) Published
Abstract [en]

Wave power has the potential to contribute significantly to sustainability by reducing our global dependence on fossil fuels. Due to harsh conditions and high costs associated with offshore testing, lab experiments are favourable for resource-efficient validation and optimization in developing Wave Energy Converter (WEC) technologies. The limited scale and availability of existing wave tanks, and the limited flexibility of existing dry test rigs does however put significant restraints on such experiments. In this paper we introduce an alternative novel robotized dry test rig concept for wave power, evaluate its performance and discuss its potential. A full-scale robotized dry test rig demonstrator is constructed and used for experiments with a WEC prototype device. High motion flexibility and accuracy is thereby validated, also for repeating recorded wave and buoy motions. Compared to other dry test rigs, no special components were used and the motion trajectories were defined in full 6-Degrees-Of-Freedom. Two real-time hydrodynamic motion response methods are also demonstrated in the test rig, enabling emulation of actual offshore operation as well as development of advanced WEC control strategies. With a larger industrial robot manipulator, the introduced test rig concept could achieve realistic scaled force and power experiments with most point absorber WECs.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Dry test rig, Wave emulator, Industrial robot, Wave energy converter, Renewable energy
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-509121 (URN)10.1016/j.seta.2023.103393 (DOI)001124250700001 ()
Available from: 2023-08-15 Created: 2023-08-15 Last updated: 2024-12-10Bibliographically approved
4. Robotized manufacturing of rubber components for commercialization of the Uppsala University wave energy converter concept
Open this publication in new window or tab >>Robotized manufacturing of rubber components for commercialization of the Uppsala University wave energy converter concept
2016 (English)Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Glasgow, UK: , 2016
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-334547 (URN)
Conference
2nd International Conference on Offshore Renewable Energy
Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2024-12-10
5. Robotized Surface Mounting of Permanent Magnets
Open this publication in new window or tab >>Robotized Surface Mounting of Permanent Magnets
2014 (English)In: Machines, Vol. 2, no 4, p. 219-232Article in journal (Refereed) Published
Abstract [en]

Using permanent magnets on a rotor can both simplify the design and increase the efficiency of electric machines compared to using electromagnets. A drawback, however, is the lack of existing automated assembly methods for large machines. This paper presents and motivates a method for robotized surface mounting of permanent magnets on electric machine rotors. The translator of the Uppsala University Wave Energy Converter generator is used as an example of a rotor. The robot cell layout, equipment design and assembly process are presented and validated through computer simulations and experiments with prototype equipment. A comparison with manual assembly indicates substantial cost savings and an improved work environment. By using the flexibility of industrial robots and a scalable equipment design, it is possible for this assembly method to be adjusted for other rotor geometries and sizes. Finally, there is a discussion on the work that remains to be done on improving and integrating the robot cell into a production line.

National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-237449 (URN)10.3390/machines2040219 (DOI)
Available from: 2014-12-02 Created: 2014-12-02 Last updated: 2024-12-10
6. Variable renewable energy sources for powering reverse osmosis desalination, with a case study of wave powered desalination for Kilifi, Kenya
Open this publication in new window or tab >>Variable renewable energy sources for powering reverse osmosis desalination, with a case study of wave powered desalination for Kilifi, Kenya
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2020 (English)In: Desalination, ISSN 0011-9164, E-ISSN 1873-4464, Vol. 494, no 114669Article in journal (Refereed) Published
Abstract [en]

An analysis of reverse osmosis powered by ocean wave power is provided. A commercially available desalination system is connected via a DC/AC converter to a variable DC source and the input voltage is altered to emulate the response of a renewable energy system. Specifically, wave data from Kilifi in Kenya during 2015 is used. The wave resource variations provide variations in estimated power output from a wave energy converter, as well as in estimated freshwater production from a wave powered desalination system. Up to three wave energy converters for desalination are investigated for Kilifi. Also, a hybrid system including solar and wave power is proposed. The experiments show that reverse osmosis desalination systems can function at power levels below the rated values, but with lower freshwater flowrates. It is concluded that wave power, or wave power combined with PV systems, may be considered as power sources for desalination, with or without battery storage.

Place, publisher, year, edition, pages
Elsevier BV, 2020
Keywords
Reverse osmosis desalination, Ocean wave power, Renewable energy sources, Freshwater, Vågkraft, avsaltning
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-417909 (URN)10.1016/j.desal.2020.114669 (DOI)000571849600003 ()
Funder
Swedish Research CouncilStandUp
Available from: 2020-08-27 Created: 2020-08-27 Last updated: 2024-12-10Bibliographically approved
7. Emulating Wave Energy Converter operation in irregular waves using a robotized dry test rig
Open this publication in new window or tab >>Emulating Wave Energy Converter operation in irregular waves using a robotized dry test rig
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Wave Energy Converter (WEC) technology has for a long time captured the interest of researchers, in the strive to increase and diversify the share of renewables in our global energy system. The development of WECs is however challenging due to the time-consuming and expensive open sea experiments required. Controlled wave tank testing is therefore often used, but suffer from the limited availability, scale and wave conditions that can be achieved. Another option is dry test rigs, utilizing a mechanical actuator to emulate WEC operation in ocean waves. Achieving realistic tests is however a challenge.

This work focuses on a robotized dry test rig, providing a cost-effective, industrial and flexible test concept for one-body and two-body emulation of point-absorber WECs in in all six degree of freedom. A numerical linear potential flow hydrodynamic force model for simulating the motions in irregular waves is presented and evaluated against wave tank experiments, before being implemented on the robot controller. Test rig experiments based on a simulated WEC damping force and assuming a one-body system acting purely in heave are presented.

We successfully demonstrated WEC operation emulation in irregular waves with the robot test rig, and were also able to evaluate its accuracy. It can be concluded that the robot performs well in relation to the numerical model, while the numerical model performs satisfying mainly for smaller and non-steep waves. Further work is therefore suggested on expanding the emulation to several degrees of freedom and also to include a physical WEC power take-off unit.

Keywords
Dry test rig, Industrial robot, Wave Energy Converter, Hydrodynamic modelling, Irregular waves
National Category
Robotics
Research subject
Engineering science with specialization in Applied Mechanics; Engineering Science with specialization in industrial engineering and management
Identifiers
urn:nbn:se:uu:diva-544284 (URN)
Note

Artikeln har inlämnats/submitted

Available from: 2024-12-03 Created: 2024-12-03 Last updated: 2025-02-05
8. Demonstrating real-time hydrodynamic motion response in force control for regular waves in a robotized dry test rig with a point-absorber WEC
Open this publication in new window or tab >>Demonstrating real-time hydrodynamic motion response in force control for regular waves in a robotized dry test rig with a point-absorber WEC
2023 (English)In: Proceedings of the 15th European Wave and Tidal Energy Conference, Bilbao, 3-7 September 2023. / [ed] Jesús María Blanco Ilzarbe, Bilbao: European Wave and Tidal Energy Conference , 2023, Vol. 15Conference paper, Published paper (Refereed)
Abstract [en]

A 6-Degrees-Of-Freedom robotized dry test rig has been developed at Uppsala University to test point absorbing WECs (Wave Energy Converters). Using a six joint industrial robot as a buoy movement emulator, the robot's outermost point (joint 6) is connected to the wire from the generator concept WEC PTO (Power Take-Off). The robot's movement in joint 6 thus corresponds to the buoy movement on the sea surface. The test rig can be used for various point absorbing WEC PTO units. In this project, the test rig has been used with a WEC-PTO prototype. The point absorbing WEC-LRTC concept is being developed at Uppsala University. The generator concept is made up of two identical rotating generators. A wire is used as a connection between the generator concept at the seabed and a buoy on the sea surface.  The goal of this article is to demonstrate and evaluate how the test rig interacts with the LRTC-WEC PTO in regular waves. In the presented experiments, a hydrodynamic model with force control method has been used.  The results show a clear difference in the use of the hydrodynamic model with different sizes of the buoy. The test rig with the force control model can be used easily to test different theoretical buoys and different load settings for WEC PTOs. Effective experiments can be performed with real PTO forces instead of simplified simulations.  Future work is to experiment with the position control method and also experiments with irregular waves.

Place, publisher, year, edition, pages
Bilbao: European Wave and Tidal Energy Conference, 2023
Keywords
LRTC, point-absorber, dry test rig, wave emulator, industrial robot, wave energy converter
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-518384 (URN)10.36688/ewtec-2023-643 (DOI)
Conference
15th European Wave and Tidal Energy Conference (EWTEC)
Available from: 2023-12-18 Created: 2023-12-18 Last updated: 2024-12-10Bibliographically approved
9. Evaluating position control for real-time hydrodynamic motion response in a robotized dry test rig with a point-absorber wave energy converter
Open this publication in new window or tab >>Evaluating position control for real-time hydrodynamic motion response in a robotized dry test rig with a point-absorber wave energy converter
2024 (English)In: Proceedings of the ASME 2024 43rd International Conference on Ocean, Offshore and Arctic Engineering: Volume 1: Offshore Technology, Singapore, 2024, Vol. 1Conference paper, Published paper (Refereed)
Abstract [en]

A robotized dry test rig in six degrees of freedom, for emulating the influence of hydrodynamic forces on and the resulting motion response of different types of point absorbing wave energy converters has been developed at Uppsala University. In the past we have investigated and shown that the dry test rig works with both force and position control methods.In this article we further examine the position control method, as we have not been able to use it for rougher wave movements. This is due to the fact that there has been a control lag in the system which contributed to the system becoming unbalanced in some emulation scenarios. A solution for an updated position control method, with significantly reduced control lag, is demonstrated in robot simulations and compared with both hydrodynamic model simulations and physical robot experiments for two buoy sizes in regular waves.

The results show a clear positive solution for avoiding control lag problems, making the position control method fully possible to use in the field. Future work is to implement the updated method on the physical robot test rig.

Place, publisher, year, edition, pages
Singapore: , 2024
Keywords
dry test rig, industrial robot, point-absorber, wave emulator, wave energy converter
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-540698 (URN)10.1115/OMAE2024-121981 (DOI)
Conference
ASME 2024 43rd International Conference on Ocean, Offshore and Arctic Engineering
Available from: 2024-10-18 Created: 2024-10-18 Last updated: 2024-12-10
10. Low-RPM torque converter (LRTC) with Integrated direct shaft flywheel
Open this publication in new window or tab >>Low-RPM torque converter (LRTC) with Integrated direct shaft flywheel
2023 (English)In: International Marine Energy Journal, E-ISSN 2631-5548, Vol. 6, no 1, p. 1-10Article in journal (Refereed) Published
Abstract [en]

The low-RPM Torque Converter (LRTC) is a rotating generator concept for use on the seabed with the driving force from sea waves motion on the sea surface. This concept is built up of two identical generators connected opposite each other via a spring drum with a built-in ball bearing clutch. The drum is connected to a buoy on the sea surface via a wire, the wire is rolled around the spring drum. With sea waves, the buoy moves either upwards or downwards and pulls the wire upwards or downwards. This movement causes the generators to spin.

This article presents an upgrade of the LRTC generator concept and upgraded measurement system, both hardware and software.

A flywheel system of the thin-disc type has been designed for direct connection to the generator's rotor shaft and an electronic measuring system has also been developed for more accurate measurements and minor disturbances.

More detailed tests have been performed both for the purpose of comparing the systems and to explore the performance of the generator concept in more detail.

Three different experiments have been done in this article. The first two experiments were performed to investigate the performance of the flywheel and to see the performance of the LRTC system with and without flywheel.

The third experiment investigated the optimization of the flywheel mass by increasing the mass of the flywheel with the addition of more thin discs.

All movements are simulated with a six-joint industrial robot. Several sinusoidal types of wave motions have been simulated with different time periods and also several real wave climate motions (data taken from fields) have been simulated with the robot. The experiments show that the addition of the flywheel in the LRTC system provides advantages in increasing both peak power, average output power and also softens the output power oscillation.

Keywords
LRTC; Flywheel; Robot; Generator; Wave energy; Renewable energy
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-501121 (URN)10.36688/imej.6.1-10 (DOI)
Available from: 2023-05-02 Created: 2023-05-02 Last updated: 2024-12-10
11. Low-RPM Torque Converter (LRTC)
Open this publication in new window or tab >>Low-RPM Torque Converter (LRTC)
2021 (English)In: Energies, E-ISSN 1996-1073, Vol. 14, no 16, article id 5071Article in journal (Refereed) Published
Abstract [en]

The concept concerned in this paper is based on energy conversion of the ocean waves via rotational generators. The objective of this research is to develop a new type of slow-motion converter. The LRTC device consists of a drum that is connected via wire to a floating buoy. The drum is connected to rotary generators. The generators are heavily braked when the direction of movement changes (up/down); this is because the generators have been charged the maximum load in order to obtain maximum output power. For upcoming improvement, the generators should have some power storage as flywheel. In the future experiments, the torque converter can even be tuned to rotate in resonance with the incoming waves, strongly increasing power absorption. Constant force springs are applied for this purpose. The focus of this project is, therefore, a new generation of wave power device for utility-scale energy conversion offering a cost of energy that can compete with established energy resources.

Place, publisher, year, edition, pages
MDPIMDPI AG, 2021
Keywords
wave energy conversion, torque converter, resonance frequency
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Energy Engineering
Identifiers
urn:nbn:se:uu:diva-455502 (URN)10.3390/en14165071 (DOI)000690643600001 ()
Funder
StandUp
Available from: 2021-10-07 Created: 2021-10-07 Last updated: 2024-12-10Bibliographically approved

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