Force and displacement measurements have been performed in situ on the piston rod mechanical lead-through transmission in the direct drive of the second experimental wave energy converter (WEC) 3 km offshore at the Lysekil research site (LRS) during a 130-day continuous full-scale experiment in 2009. The direct drive consists of a buoy line and a piston rod transmission with a double-hinged link (DHL) at the lower end connecting the point absorbing surface-floating buoy to the translator of an encapsulated permanent magnet linear generator on the seabed. The buoy line is guided by a funnel in the buoy line guiding system 3.2 m above the generator capsule. The 3 m long piston rod reciprocates through a mechanical lead-through in the capsule wall, sealing off seawater from entering the generator capsule. A setup of laser triangulation sensors measures the relative lateral displacement of the piston rod. This paper introduces a method and a system of equations for calculating piston rod relative tilt angle and piston rod azimuth direction of tilting from the relative lateral displacement measurements. Correlation with piston rod axial displacement and forces enables evaluation of the three-dimensional (3D) oscillation dynamics. Results are presented from 2 weeks after launch and from 3 months after launch in altogether four cases representing two different stages of wear in two different sea states. Piston rod tilting from accumulated wear in the buoy line guiding system is separated from tilting due to elastic displacement. Structural mechanical finite element method (FEM) simulations verify the magnitude of elastic displacement and indicate negligible stress and strain at the mounting point of the laser sensor setup. The proposed theory for piston rod 3D motion is validated by the experiment. As the experiment progressed, wear in the buoy line guiding system accelerated due to splitting of the buoy line jacketing compound, thereby increasing the piston rod tilt angles. Over 94 days into the experiment, 21.8 mm of accumulated wear in the buoy line guiding system had altered the characteristics of the piston rod oscillations and increased the maximum piston rod relative tilt angle by 0.39 deg in the predominant azimuth direction of wave propagation. Further accumulated wear in the buoy line guiding system led to buoy line rupture 130 days after launch. The results presented in this paper have been used in assessments for improving the mechanical subsystems in subsequent experimental WECs based on the Uppsala concept.
Skip Nav Destination
Article navigation
June 2016
Research-Article
Three-Dimensional Oscillation Dynamics of the In Situ Piston Rod Transmission Between Buoy Line and the Double Hinge-Connected Translator in an Offshore Linear Wave Energy Converter Available to Purchase
Erland Strömstedt,
Erland Strömstedt
Division of Electricity,
Department of Engineering Sciences,
Swedish Centre for Renewable
Electric Energy Conversion,
Uppsala University,
P.O. Box 534,
Uppsala SE-751 21, Sweden
e-mail: [email protected]
Department of Engineering Sciences,
Swedish Centre for Renewable
Electric Energy Conversion,
Uppsala University,
P.O. Box 534,
Uppsala SE-751 21, Sweden
e-mail: [email protected]
Search for other works by this author on:
Mats Leijon
Mats Leijon
Mem. ASME
Division of Electricity,
Department of Engineering Sciences,
Swedish Centre for Renewable
Electric Energy Conversion,
Uppsala University,
P.O. Box 534,
Uppsala SE-751 21, Sweden
e-mail: [email protected]
Division of Electricity,
Department of Engineering Sciences,
Swedish Centre for Renewable
Electric Energy Conversion,
Uppsala University,
P.O. Box 534,
Uppsala SE-751 21, Sweden
e-mail: [email protected]
Search for other works by this author on:
Erland Strömstedt
Division of Electricity,
Department of Engineering Sciences,
Swedish Centre for Renewable
Electric Energy Conversion,
Uppsala University,
P.O. Box 534,
Uppsala SE-751 21, Sweden
e-mail: [email protected]
Department of Engineering Sciences,
Swedish Centre for Renewable
Electric Energy Conversion,
Uppsala University,
P.O. Box 534,
Uppsala SE-751 21, Sweden
e-mail: [email protected]
Mats Leijon
Mem. ASME
Division of Electricity,
Department of Engineering Sciences,
Swedish Centre for Renewable
Electric Energy Conversion,
Uppsala University,
P.O. Box 534,
Uppsala SE-751 21, Sweden
e-mail: [email protected]
Division of Electricity,
Department of Engineering Sciences,
Swedish Centre for Renewable
Electric Energy Conversion,
Uppsala University,
P.O. Box 534,
Uppsala SE-751 21, Sweden
e-mail: [email protected]
1Corresponding author.
Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received August 19, 2012; final manuscript received October 29, 2015; published online March 18, 2016. Assoc. Editor: Hideyuki Suzuki.
J. Offshore Mech. Arct. Eng. Jun 2016, 138(3): 031901 (21 pages)
Published Online: March 18, 2016
Article history
Received:
August 19, 2012
Revised:
October 29, 2015
Citation
Strömstedt, E., and Leijon, M. (March 18, 2016). "Three-Dimensional Oscillation Dynamics of the In Situ Piston Rod Transmission Between Buoy Line and the Double Hinge-Connected Translator in an Offshore Linear Wave Energy Converter." ASME. J. Offshore Mech. Arct. Eng. June 2016; 138(3): 031901. https://doi.org/10.1115/1.4031972
Download citation file:
Get Email Alerts
Cited By
Hydrodynamic Responses of a Moored Semi-submersible Floating Offshore Wind Turbine in Steep Waves
J. Offshore Mech. Arct. Eng
Investigation into the hydrodynamic performance of Gate rudder maneuvering under wake conditions
J. Offshore Mech. Arct. Eng
A Shock-Absorbing Non-Hydrostatic Solver on σ-Grids for Wave Modeling Over Complex Bathymetry
J. Offshore Mech. Arct. Eng
Related Articles
Power Absorption Modeling and Optimization of a Point Absorbing Wave Energy Converter Using Numerical Method
J. Energy Resour. Technol (June,2014)
The Effect of Environmental Contour Selection on Expected Wave Energy Converter Response
J. Offshore Mech. Arct. Eng (February,2019)
Evaluating Constant DC-Link Operation of Wave Energy Converter
J. Dyn. Sys., Meas., Control (January,2014)
Latching Control of an Oscillating Water Column Spar-Buoy Wave Energy Converter in Regular Waves
J. Offshore Mech. Arct. Eng (May,2013)
Related Proceedings Papers
Related Chapters
Case Study 10: Data Reconciliation
Engineering Optimization: Applications, Methods, and Analysis
Self-Induced and Machine-Induced Specimen Vibrations in Fretting Testing
Effects of Mechanical Stiffness and Vibration on Wear
Performance Evaluation Through Laboratory and Field Tests
Computer Vision for Structural Dynamics and Health Monitoring