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Leijon, Mats
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Publications (10 of 255) Show all publications
Hultman, E. & Leijon, M. (2018). An updated cable feeder tool design for robotized stator cable winding. Mechatronics (Oxford), 49, 197-210
Open this publication in new window or tab >>An updated cable feeder tool design for robotized stator cable winding
2018 (English)In: Mechatronics (Oxford), ISSN 0957-4158, E-ISSN 1873-4006, Vol. 49, p. 197-210Article in journal (Refereed) Published
Abstract [en]

We have previously suggested a method for robotized stator winding of cable wound electric machines and demonstrated the method successfully in full-scale experiments. The cable feeder tool used to handle the cable during the complete winding process is an essential component of this robot cell. To take the robot winding method to the next level, into an industrial product, require further developments regarding durability, independency, flexibility and implementability. In this paper, we present an updated cable feeder tool design. This tool is designed to be used in a robot cell for cable winding of the third-generation design of the Uppsala University Wave Energy Converter generator stator. In this work, three cable feeder tool prototypes have been constructed, experimentally evaluated and validated for the intended application. Key performance parameters are presented and discussed, including suggestions for further developments. We completed a durable, compact, high performance tool design, with fully integrated control into industrial robot controllers. The experimental results presented in this article are very promising and hence, the updated cable feeder tool design represents another important step towards an industrial solution for robotized stator cable winding.

National Category
Robotics Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-334553 (URN)10.1016/j.mechatronics.2018.01.006 (DOI)
Available from: 2017-11-23 Created: 2017-11-23 Last updated: 2018-04-26Bibliographically approved
Leijon, J., Sjölund, J., Ekergard, B., Boström, C., Eriksson, S., Temiz, I. & Leijon, M. (2018). Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power. Energies, 11(1), Article ID 84.
Open this publication in new window or tab >>Study of an Altered Magnetic Circuit of a Permanent Magnet Linear Generator for Wave Power
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2018 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 11, no 1, article id 84Article in journal (Refereed) Published
Abstract [en]

The wave energy converter (WEC) studied and developed at Uppsala University in Sweden is a point absorbing buoy connected to a linear generator (LG) on the seabed. Previous studies have improved the sustainability of the generator, changing its magnets from Nd2Fe14B-magnets to ferrites. In this paper, the magnetic circuit of the linear generator is further studied. Ferrite magnets of two different types (Y30 and Y40) are studied along with different shapes of pole shoes for the system. The finite element method (FEM) simulations in a program called Ace are performed. The results show that a linear generator including both Y30 and Y40 magnets and shortened T-shaped pole shoes can generate a similar magnetic energy in the airgap as a linear generator only containing Y40 magnets and rectangular pole shoes. This shows that the magnetic circuit can be altered, opening up sizes and strengths of magnets for different retailers, and thereby possibly lowering magnet cost and transportation. This work was previously presented as a conference at the European Wave and Tidal Energy Conference (EWTEC) 2017 in Cork, Ireland; this manuscript has been carefully revised and some discussions, on magnet costs for example, have been added to this paper.

Keywords
wave energy converter (WEC), linear generator (LG), ferrite permanent magnets (PMs), renewable energy sources
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-348930 (URN)10.3390/en11010084 (DOI)000424397600084 ()
Funder
Swedish Research Council, 2015-03126Swedish Energy Agency, P42243-1
Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-04-26Bibliographically approved
Hultman, E. & Leijon, M. (2017). Automated Cable Preparation for Robotized Stator Cable Winding. MACHINES, 5(2), Article ID 14.
Open this publication in new window or tab >>Automated Cable Preparation for Robotized Stator Cable Winding
2017 (English)In: MACHINES, ISSN 2075-1702, Vol. 5, no 2, article id 14Article in journal (Refereed) Published
Abstract [en]

A method for robotized cable winding of the Uppsala UniversityWave Energy Converter generator stator has previously been presented and validated. The purpose of this study is to present and validate further developments to the method: automated stand-alone equipment for the preparation of the winding cables. The cable preparation consists of three parts: feeding the cable from a drum, forming the cable end and cutting the cable. Forming and cutting the cable was previously done manually and only small cable drums could be handled. Therefore the robot cell needed to be stopped frequently. The new equipment was tested in an experimental robot stator cable winding setup. Through the experiments, the equipment was validated to be able to perform fully automated and robust cable preparation. Suggestions are also given on how to further develop the equipment with regards to performance, robustness and quality. Hence, this work represents another important step towards demonstrating completely automated robotized stator cable winding.

Keywords
cable winding, industrial automation, industrial robot, electric machine assembly, wave energy converter
National Category
Robotics
Identifiers
urn:nbn:se:uu:diva-324239 (URN)10.3390/machines5020014 (DOI)000401525400004 ()
Available from: 2017-06-15 Created: 2017-06-15 Last updated: 2017-12-07Bibliographically approved
Kamf, T. & Leijon, M. (2017). Automated Mounting of Pole-Shoe Wedges in Linear Wave Power Generators-Using Industrial Robotics and Proximity Sensors. MACHINES, 5(1), Article ID 10.
Open this publication in new window or tab >>Automated Mounting of Pole-Shoe Wedges in Linear Wave Power Generators-Using Industrial Robotics and Proximity Sensors
2017 (English)In: MACHINES, ISSN 2075-1702, Vol. 5, no 1, article id 10Article in journal (Refereed) Published
Abstract [en]

A system for automatic mounting of high tolerance wedges inside a wave power linear generator is proposed. As for any renewable energy concept utilising numerous smaller generation units, minimising the production cost per unit is vital for commercialization. The linear generator in question uses self-locking wedges, which are challenging to mount using industrial robots due to the high tolerances used, and because of the fact that any angular error remaining after calibration risks damaging the equipment. Using two types of probes, mechanical touch probes and inductive proximity sensors, combined with a flexible robot tool and iterative calibration routines, an automatic mounting system that overcomes the challenges of high tolerance wedge mounting is presented. The system is experimentally verified to work at mounting speeds of up to 50mms(-1), and calibration accuracies of 0.25mm and 0.1 degrees are achieved. The use of a flexible robot tool, able to move freely in one Cartesian plane, was found to be essential for making the system work.

Place, publisher, year, edition, pages
MDPI AG, 2017
Keywords
automated production, wave power, robotics, calibration, sensors, wedges, linear-generator, touch probe
National Category
Environmental Engineering
Identifiers
urn:nbn:se:uu:diva-324353 (URN)10.3390/machines5010010 (DOI)000401524900009 ()
Funder
VINNOVA
Available from: 2017-06-14 Created: 2017-06-14 Last updated: 2017-10-08Bibliographically approved
Sjökvist, L., Göteman, M., Rahm, M., Waters, R., Svensson, O., Strömstedt, E. & Leijon, M. (2017). Calculating Buoy Response for a Wave Energy Converter - a Comparsion Between Two Computational Methods and Experimental Results [Letter to the editor]. Theoretical and Applied Mechanics Letters, 7(3), 164-168
Open this publication in new window or tab >>Calculating Buoy Response for a Wave Energy Converter - a Comparsion Between Two Computational Methods and Experimental Results
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2017 (English)In: Theoretical and Applied Mechanics Letters, ISSN 2095-0349, Vol. 7, no 3, p. 164-168Article in journal, Letter (Refereed) Published
Abstract [en]

When designing a wave power plant, reliable and fast simulation tools are required. Computational fluid dynamics (CFD) software provides high accuracy but with a very high computational cost, and in operational, moderate sea states, linear potential flow theories may be sufficient to model the hydrodynamics. In this paper, a model is built in COMSOL Multiphysics to solve for the hydrodynamic parameters of a point-absorbing wave energy device. The results are compared with a linear model where the hydrodynamical parameters are computed using WAMIT, and to experimental results from the Lysekil research site. The agreement with experimental data is good for both numerical models.

National Category
Marine Engineering
Identifiers
urn:nbn:se:uu:diva-328498 (URN)10.1016/j.taml.2017.05.004 (DOI)000416966800008 ()
Funder
Natural‐Disaster ScienceSwedish Research Council, 2015-04657
Available from: 2017-08-24 Created: 2017-08-24 Last updated: 2018-03-07Bibliographically approved
Elamalayil Soman, D. & Leijon, M. (2017). Cross-Regulation Assessment of DIDO Buck-Boost Converter for Renewable Energy Application. Energies, 10(7), Article ID 846.
Open this publication in new window or tab >>Cross-Regulation Assessment of DIDO Buck-Boost Converter for Renewable Energy Application
2017 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 10, no 7, article id 846Article in journal (Refereed) Published
Abstract [en]

When medium- or high-voltage power conversion is preferred for renewable energy sources, multilevel power converters have received much of the interest in this area as methods for enhancing the conversion efficiency and cost effectiveness. In such cases, multilevel, multi-input multi-output (MIMO) configurations of DC-DC converters come to the scenario for integrating several sources together, especially considering the stringent regulatory needs and the requirement of multistage power conversion systems. Considering the above facts, a three-level dual input dual output (DIDO) buck-boost converter, as the simplest form of MIMO converter, is proposed in this paper for DC-link voltage regulation. The capability of this converter for cross regulating the DC-link voltage is analyzed in detail to support a three-level neutral point clamped inverter-based grid connection in the future. The cross-regulation capability is examined under a new type of pulse delay control (PDC) strategy and later compared with a three-level boost converter (TLBC). Compared to conventional boost converters, the high-voltage three-level buck boost converter (TLBBC) with PDC exhibits a wide controllability range and cross regulation capability. These enhanced features are extremely important for better regulating variable output renewable energy sources such as solar, wind, wave, marine current, etc. The simulation and experimental results are provided to validate the claim.

Keywords
dual input dual output (DIDO) converter; three-level buck boost converter (TLBBC); pulse delay control (PDC); neutral point clamped inverter; cross-regulation; renewable energy conversion
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-332725 (URN)10.3390/en10070846 (DOI)
Funder
SweGRIDS - Swedish Centre for Smart Grids and Energy Storage
Available from: 2017-11-01 Created: 2017-11-01 Last updated: 2017-12-06Bibliographically approved
Chen, W., Dolguntseva, I., Savin, A., Zhang, Y., Li, W., Svensson, O. & Leijon, M. (2017). Numerical modelling of a point-absorbing wave energy converter in irregular and extreme waves. Applied Ocean Research, 63, 90-105
Open this publication in new window or tab >>Numerical modelling of a point-absorbing wave energy converter in irregular and extreme waves
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2017 (English)In: Applied Ocean Research, ISSN 0141-1187, E-ISSN 1879-1549, Vol. 63, p. 90-105Article in journal (Refereed) Published
Abstract [en]

Based on the Navier-Stokes (RANS) equations, a three-dimensional (3-D) mathematical model for the hydrodynamics and structural dynamics of a floating point-absorbing wave energy converter (WEC) with a stroke control system in irregular and extreme waves is presented. The model is validated by a comparison of the numerical results with the wave tank experiment results of other researchers. The validated model is then utilized to examine the effect of wave height on structure displacements and connection rope tension. In the examined cases, the differences in WEC’s performance exhibited by an inviscid fluid and a viscous fluid can be neglected. Our results also reveal that the differences in behavior predicted by boundary element method (BEM) and the RANS-based method can be significant and vary considerably, depending on wave height.

Keywords
Point-absorbing WEC, CFD, Irregular waves, Extreme waves, Connection rope tension, Survivability
National Category
Marine Engineering
Identifiers
urn:nbn:se:uu:diva-313250 (URN)10.1016/j.apor.2017.01.004 (DOI)000397367100008 ()
Funder
Swedish Energy AgencyStandUp
Available from: 2017-01-18 Created: 2017-01-18 Last updated: 2017-04-21Bibliographically approved
Chatzigiannakou, M. A., Dolguntseva, I. & Leijon, M. (2017). Offshore Deployments of Wave Energy Converters by Seabased Industry AB. Journal of Marine Science and Engineering, 5(2), Article ID 15.
Open this publication in new window or tab >>Offshore Deployments of Wave Energy Converters by Seabased Industry AB
2017 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 5, no 2, article id 15Article in journal (Refereed) Published
Abstract [en]

Since 2008, Seabased Industry AB (SIAB) has manufactured and deployed several units of wave energy converters (WECs) of different design. The WECs are linear generators with point absorber buoy systems that are placed on the seabed, mounted on a gravitation concrete foundation. These deployments have taken place in different areas, using different deployment vessels. Offshore deployments of WECs and underwater substations have so far been complicated procedures, that were both expensive and time-consuming. The focus of this paper is to discuss these deployments in terms of economy and time efficiency, as well as safety. Because seven vessels have been used to facilitate the deployments, an evaluation on the above basis is carried out for them. The main conclusions and certain solutions are presented for the various problems encountered during these deployments and the vessel choice is discussed. It is found that the offshore deployment process can be optimized in terms of cost, time efficiency and safety with a careful vessel choice, use of the latest available technologies and detailed planning and organizing.

Keywords
offshore deployment; wave energy converter; specialized vessel; underwater substation
National Category
Marine Engineering
Identifiers
urn:nbn:se:uu:diva-318633 (URN)10.3390/jmse5020015 (DOI)000423689700001 ()
Available from: 2017-03-27 Created: 2017-03-27 Last updated: 2018-03-19Bibliographically approved
Frost, A. E., Ulvgård, L., Sjökvist, L., Eriksson, S. & Leijon, M. (2017). Partial Stator Overlap in a Linear Generator for Wave Power: An Experimental Study. Journal of Marine Science and Engineering, 5(4), Article ID 53.
Open this publication in new window or tab >>Partial Stator Overlap in a Linear Generator for Wave Power: An Experimental Study
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2017 (English)In: Journal of Marine Science and Engineering, E-ISSN 2077-1312, Vol. 5, no 4, article id 53Article in journal (Refereed) Published
Abstract [en]

This paper presents a study on how the power absorption and damping in a linear generator for wave energy conversion are affected by partial overlap between stator and translator. The theoretical study shows that the electrical power as well as the damping coefficient change quadratically with partial stator overlap, if inductance, friction and iron losses are assumed independent of partial stator overlap or can be neglected. Results from onshore experiments on a linear generator for wave energy conversion cannot reject the quadratic relationship. Measurements were done on the inductance of the linear generator and no dependence on partial stator overlap could be found. Simulations of the wave energy converter's operation in high waves show that entirely neglecting partial stator overlap will overestimate the energy yield and underestimate the peak forces in the line between the buoy and the generator. The difference between assuming a linear relationship instead of a quadratic relationship is visible but small in the energy yield in the simulation. Since the theoretical deduction suggests a quadratic relationship, this is advisable to use during modeling. However, a linear assumption could be seen as an acceptable simplification when modeling since other relationships can be computationally costly.

Place, publisher, year, edition, pages
MDPI AG, 2017
Keywords
Wave Power, linear generator, stator overlap, active area, end-stop forces
National Category
Energy Engineering Marine Engineering
Identifiers
urn:nbn:se:uu:diva-329833 (URN)10.3390/jmse5040053 (DOI)000423694200009 ()
Available from: 2017-09-21 Created: 2017-09-21 Last updated: 2018-03-19Bibliographically approved
Forslund, J., Thomas, K. & Leijon, M. (2017). Power And Energy Needed For Starting A Vertical Axis Marine Current Turbine. In: : . Paper presented at Proceedings of the 12th European Wave and Tidal Energy Conference 27th Aug -1st Sept 2017, Cork, Ireland.
Open this publication in new window or tab >>Power And Energy Needed For Starting A Vertical Axis Marine Current Turbine
2017 (English)Conference paper, Published paper (Refereed)
Abstract [en]

A marine current power station has been deployedin Söderfors, Sweden. It comprises a five bladed fixed pitchvertical axis H-rotor turbine directly connected to a permanentmagnet synchronous generator. The turbine is rated for 1.3m/s, but at lower water speeds the turbine is generally not selfstarting. This paper investigates the energy and power neededto at low speeds start the turbine electrically with a BrushLessDC (BLDC) motor until the turbines gives a net positive torqueto the generator. A range of startup BLDC powers have beeninvestigated. It is shown that for three water speeds (0.98 m/s, 1.04m/s and 1.16 m/s) the energy needed for start up is equivalent toless than 1.2 s of power production at maximum power captureof the turbine. The startup time is mostly dependent on BLDCpower setting, not on water speed. A BLDC power of 1/7th ofrated power of the machine is enough to start the machine within2 seconds. The results suggest that a higher BLDC power thanthat will not significantly reduce the startup time nor reduce theenergy needed (increase the efficiency of the startup process).The water speed has the highest impact on the time it takes torecover the energy needed for startup once the BLDC power iswell above the losses in the system.

Keywords
Marine current power, startup energy, Söderfors, vertical axis turbine
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-330188 (URN)
Conference
Proceedings of the 12th European Wave and Tidal Energy Conference 27th Aug -1st Sept 2017, Cork, Ireland
Projects
Marine Current Power
Funder
Vattenfall ABStandUpÅForsk (Ångpanneföreningen's Foundation for Research and Development)J. Gust. Richert stiftelse
Available from: 2017-09-27 Created: 2017-09-27 Last updated: 2018-04-10Bibliographically approved
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