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The invention provides optimal control of a three-degree-of-freedom wave energy converter using a pseudo-spectral control method. The three modes are the heave, pitch and surge. A 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. The invention can use a Fourier series as basis functions to approximate the states and the control. For the parametric excited case, a sequential quadratic programming approach can be implemented to numerically solve for the optimal control. The 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.
US 10,344,736 B2
National Technology & Engineering Solution of Sandia, LLC
Michigan Technological University
Certificate of Correction
Engineering Mechanics | Mechanical Engineering
Abdelkhalik, Ossama; Bacelli, Giorgio; Zou, Shangyan; Robinett, Rush D. III; Wilson, David G.; and Coe, Ryan G., "Pseudo-spectral method to control three-degree-of-freedom wave energy converters" (2019). Michigan Tech Patents. 142.