Nonlinear control design for a spherical Wave Energy Converter

This paper discusses the development of two nonlinear controls for a nonlinear spherical wave energy converter (WEC) to maximize the energy it harvests from the waves. The first control is a simple nonlinear damping control, which is designed based on the hydrodynamic damping coefficients. These control coefficients are then optimized using a Genetic Algorithm. The second is a nonlinear optimal control derived analytically using the Pontryagin minimum principle for comparison. The study found that the nonlinear optimal control improves the device's performance by effectively leveraging the hydrodynamic nonlinearity from the floater's shape. The nonlinear bang-singular-bang (BSB) control showed an average 20% performance improvement over the nonlinear damping control (NLDC).