Multi-objective optimal control for energy extraction and lifetime maximisation in dielectric elastomer wave energy converters

In this paper, we model the multi-objective optimisation problem for maximising the energetic performance while minimising the damage accumulation in ocean wave energy converters based on dielectric elastomer generators (DEGs). DEGs are electrostatic smart-material-based transducers that are cheaper, lighter, and more adaptable to the marine environment than conventional power take-off systems. Because DEGs are prone to electrical breakdown upon cyclic loading, identifying trade-offs between achievable performance and lifetime is currently a crucial research question. Based on some assumptions on the system layout and material properties, and using the methods of Pareto optimisation, we prove that a suitably chosen control strategy can potentially achievez a dramatic reduction in the accumulated damage at the expense of a small reduction in the harvested energy. We further compare the Pareto optimal control solutions with commonly used control heuristics for DEGs, showing that optimal control can provide a reduction in the accumulated damage while preserving (or even improving) the energy performance.