Linear optimal control on a multi-PTO wave energy converter M4 with performance analysis

It has been shown in many studies that control can improve the power capture of Wave Energy Converters (WECs). However, the majority has focused on simple point absorber WECs with one Power Take Off (PTO). As WEC design evolves, multi-PTO WECs have shown improved power capture. This raises the challenge of designing a controller to control multiple PTOs simultaneously. In this paper, we demonstrate that the previous proposed linear optimal controller can be re-designed to tackle multi-PTO WEC control problem. The 8-float 1-3-4 format M4 WEC with four parallel PTOs is chosen as a case study. The M4 design has been shown by experiments to be predominantly linear thus ideal for control design. The hydrodynamic couplings between different floats of the WEC are fully considered in the control-oriented state-space model. Numerical results show that the linear optimal control enables improvement of power capture of all PTOs. Application to different device headings is ongoing.