Pseudo-spectral method to control three-degree-of-freedom wave energy converters
| DWPI Title: Multi-resonant multiple degree-of-freedom wave energy converter, has predictor that is configured to predict excitation force of wave impacting buoy in surge and pitch directions in future time horizon |
| Abstract: 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. |
| Use: Multi-resonant multiple degree-of-freedom wave energy converter. |
| Advantage: The multi-resonant multiple degree-of-freedom wave energy converter selects the Fourier series to be the basis function and therefore derivative and integration of the approximation can be computed easier than the other orthogonal polynomials. The radiation forces are approximated using the Fourier series representation for the states, while eliminating the need for convolution integral evaluation. |
| Novelty: The converter (100) has a heave controller (114) that causes the power take-off (110) to apply a force to the buoy (102). A predictor (120) is configured to predict the excitation force of the wave impacting the buoy in the surge and pitch directions in a future time horizon in which the control forces in the surge and pitch directions are optimized using a pseudo-spectral control method to resonant the surge and pitch motions with the predicted excitation force and the velocity of the pitch motion is selected to maximize parametric excitation of the surge-pitch motion. |
| Filed: 12/11/2017 |
| Application Number: US15837853A |
| Tech ID: SD 14143.3 |
| This invention was made with Government support under Contract No. DE-NA0003525 awarded by the United States Department of Energy/National Nuclear Security Administration. The Government has certain rights in the invention. |
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