Modelling and Control Tank Testing Validation for Attenuator Type Wave Energy Converter – Part III: Model Predictive Control and Robustness Validation

Abstract

Following the tank testing results of linear passive damping control and linear non-causal optimal control (LNOC) in the Part I and Part II papers, this paper presents further tank testing results focusing on two aspects: Firstly, a model predictive controller (MPC) is designed based on the model developed by system identification in Part I to optimally handle actuator saturation limits. The MPC control is demonstrated to significantly improve the energy output by 9.86% up to 463.42% compared with a well-tuned passive damper and can also outperform the LNOC presented in Part II in a range of irregular unidirectional waves. Secondly, the robustness of the MPC controller and the LNOC controller is validated in more realistic sea conditions when directional spreading waves and side waves are superimposed onto the dominant directional waves. The test results show that both MPC and LNOC can still significantly outperform the passive damping controller in all the sea conditions. These tank testing results pave a solid way for future sea trial testing of these advanced non-causal optimal control strategies developed for wave energy converters in sea trials.