| 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. |