LPV Estimation of Wave Excitation Forces in Wave Energy Converters via Zonotopic Kalman Filtering

Wave excitation force estimation for wave energy converters remains a significant challenge, since the vast majority of the state-of-the-art methods are not able to fully address all the requirements for a reliable estimate under nonlinear conditions, particularly when paired with optimal controllers. To address this issue, we leverage the features of zonotopic Kalman filters to deal with nonlinear effects in the system dynamics, while maintaining a reduced computational cost, demonstrating suitable optimality properties. For the optimal design of the filter, we introduce a novel quasi-LPV formulation of wave energy converters, which effectively takes into account nonlinear effects in the dynamics of the device. For estimation purposes, the wave excitation force is modelled according to the internal model principle, while the filter also provides an estimate of the system state, necessary for energy maximising optimal control. The proposed filter estimation quality is demonstrated extensively via a numerical case study, under realistic irregular wave conditions.