Adaptive Output-Feedback Optimal Control for Integrated Wave Energy Converter Platform: Design, Control and Experiment

To obtain the high-efficiency power conversion of wave energy, this paper proposes a novel mechanical design of power take-off (PTO) and wave energy converter (WEC) control strategy. Firstly, an integrated WEC-PTO model considering a permanent magnet synchronous generator (PMSG) is designed. One salient feature of this model is that a mechanical motion rectification (MMR)-based PTO is incorporated, which can transfer the reciprocating motion of float to non-reciprocating rotation of PMSG. Secondly, an adaptive output- feedback optimal WEC control method is developed. In specific, an extended state observer (ESO) is employed to accommodate the unknown system nonlinear dynamics. Then, an output algebraic Riccati equation (OARE) is derived, whose optimal solution can be computed by the system output information, thereby facilitating its real-time application. Finally, a new adaptive learning algorithm is designed to guarantee the convergence of the optimal solution. Simulation and experiment based on a small-scale integrated WEC-PTO test-rig are carried out to illustrate the feasibility of the proposed WEC control method and the conceptual working principle of the designed integrated WEC-PTO model. The experimental results show that with the help of the proposed model and WEC control method, the energy output is increased by up to 48.53%.