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Title: Control of Three Degrees-of-Freedom Wave Energy Converters Using Pseudo-Spectral Methods

Abstract

This study presents a solution to the optimal control problem of a three degrees-of-freedom (3DOF) wave energy converter (WEC). The three modes are the heave, pitch, and surge. The dynamic model is characterized by a coupling between the pitch and surge modes, while the heave is decoupled. The heave, however, excites the pitch motion through nonlinear parametric excitation in the pitch mode. This paper uses Fourier series (FS) as basis functions to approximate the states and the control. A simplified model is first used where the parametric excitation term is neglected and a closed-form solution for the optimal control is developed. For the parametrically excited case, a sequential quadratic programming approach is implemented to solve for the optimal control numerically. Numerical results show that the harvested energy from three modes is greater than three times the harvested energy from the heave mode alone. Moreover, the harvested energy using a control that accounts for the parametric excitation is significantly higher than the energy harvested when neglecting this nonlinear parametric excitation term.

Authors:
 [1];  [1];  [1];  [2];  [2];  [2]
  1. Michigan Tech Univ., Houghton, MI (United States)
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Wind and Water Technologies Office (EE-4W)
OSTI Identifier:
1485469
Report Number(s):
SAND-2018-12263J
Journal ID: ISSN 0022-0434; 669160
Grant/Contract Number:  
AC04-94AL85000
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Dynamic Systems, Measurement, and Control
Additional Journal Information:
Journal Volume: 140; Journal Issue: 7; Journal ID: ISSN 0022-0434
Publisher:
ASME
Country of Publication:
United States
Language:
English
Subject:
16 TIDAL AND WAVE POWER; Waves; Degrees of freedom; Optimization; Surges; Wave energy converters; Excitation; Optimal control; Fourier series; Dynamic models

Citation Formats

Abdelkhalik, Ossama, Zou, Shangyan, Robinett, III, Rush D., Bacelli, Giorgio, Wilson, David G., and Coe, Ryan Geoffrey. Control of Three Degrees-of-Freedom Wave Energy Converters Using Pseudo-Spectral Methods. United States: N. p., 2018. Web. doi:10.1115/1.4038860.
Abdelkhalik, Ossama, Zou, Shangyan, Robinett, III, Rush D., Bacelli, Giorgio, Wilson, David G., & Coe, Ryan Geoffrey. Control of Three Degrees-of-Freedom Wave Energy Converters Using Pseudo-Spectral Methods. United States. doi:10.1115/1.4038860.
Abdelkhalik, Ossama, Zou, Shangyan, Robinett, III, Rush D., Bacelli, Giorgio, Wilson, David G., and Coe, Ryan Geoffrey. Fri . "Control of Three Degrees-of-Freedom Wave Energy Converters Using Pseudo-Spectral Methods". United States. doi:10.1115/1.4038860. https://www.osti.gov/servlets/purl/1485469.
@article{osti_1485469,
title = {Control of Three Degrees-of-Freedom Wave Energy Converters Using Pseudo-Spectral Methods},
author = {Abdelkhalik, Ossama and Zou, Shangyan and Robinett, III, Rush D. and Bacelli, Giorgio and Wilson, David G. and Coe, Ryan Geoffrey},
abstractNote = {This study presents a solution to the optimal control problem of a three degrees-of-freedom (3DOF) wave energy converter (WEC). The three modes are the heave, pitch, and surge. The dynamic model is characterized by a coupling between the pitch and surge modes, while the heave is decoupled. The heave, however, excites the pitch motion through nonlinear parametric excitation in the pitch mode. This paper uses Fourier series (FS) as basis functions to approximate the states and the control. A simplified model is first used where the parametric excitation term is neglected and a closed-form solution for the optimal control is developed. For the parametrically excited case, a sequential quadratic programming approach is implemented to solve for the optimal control numerically. Numerical results show that the harvested energy from three modes is greater than three times the harvested energy from the heave mode alone. Moreover, the harvested energy using a control that accounts for the parametric excitation is significantly higher than the energy harvested when neglecting this nonlinear parametric excitation term.},
doi = {10.1115/1.4038860},
journal = {Journal of Dynamic Systems, Measurement, and Control},
number = 7,
volume = 140,
place = {United States},
year = {2018},
month = {1}
}

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