Date of Award

2024

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering-Engineering Mechanics (PhD)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Gordon G. Parker

Committee Member 1

Wayne W. Weaver

Committee Member 2

Hassan Masoud

Committee Member 3

Guy Meadows

Committee Member 4

Frederick Driscoll

Abstract

The growing urgency to transition towards carbon-neutral energy sources has sparked significant interest in diversifying energy portfolios by incorporating renewable energies, including the untapped potential of wave energy. This dissertation sets its objectives in advancing wave energy converter (WEC) technologies by focusing on developing and validating a nonlinear modeling technique and designing control strategies to maximize energy extraction and enhance WEC efficiency. At the heart of this research is the derivation and validation of an algebraic nonlinear Froude-Krylov forces model. Building on this foundational model, a robust nonlinear sliding mode controller and a nonlinear model predictive controller are designed to optimize the performance of the WEC. These contributions address critical challenges in the wave energy community, such as the high levelized cost of energy (LCOE), the inefficiency of traditional control systems, and the operational constraints under several sea conditions. The derived nonlinear model significantly improves the accuracy of WEC modeling, promising enhanced predictive capabilities over traditional linear models, especially under large wave amplitudes and frequencies. The sliding mode and nonlinear predictive controllers demonstrated superior performance in robustness and energy optimization, respectively, suggesting significant reductions in LCOE and operational costs. These significant performance improvements demonstrate the potential of advancing WEC controllers, by driving wave energy closer to commercial viability.

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