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Reactive control of a two-body point absorber using reinforcement learning


Citation Anderlini, E., Forehand, D.I.M., Bannon, E., Xiao, Q. and Abusara, M. Reactive control of a two-body point absorber using reinforcement learning, Ocean Engineering, 148: 650-658, 2018. https://doi.org/10.1016/j.oceaneng.2017.08.017.
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Author(s) Anderlini, E., Forehand, D.I.M., Bannon, E., Xiao, Q. and Abusara, M.
Project partner(s) University of Edinburgh, Wave Energy Scotland, University of Strathclyde, University of Exeter
Publisher Ocean Engineering, 148: 650-658
DOI https://doi.org/10.1016/j.oceaneng.2017.08.017
Abstract In this article, reinforcement learning is used to obtain optimal reactive control of a two-body point absorber. In particular, the Q-learning algorithm is adopted for the maximization of the energy extraction in each sea state. The controller damping and stiffness coefficients are varied in steps, observing the associated reward, which corresponds to an increase in the absorbed power, or penalty, owing to large displacements. The generated power is averaged over a time horizon spanning several wave cycles due to the periodicity of ocean waves, discarding the transient effects at the start of each new episode. The model of a two-body point absorber is developed in order to validate the control strategy in both regular and irregular waves. In all analysed sea states, the controller learns the optimal damping and stiffness coefficients. Furthermore, the scheme is independent of internal models of the device response, which means that it can adapt to variations in the unit dynamics with time and does not suffer from modelling errors.

Highlights
  • Reinforcement learning is applied to the reactive control of a two-body WEC.
  • The algorithm finds the optimal damping and stiffness coefficients.
  • A time averaged approach is adopted.
  • The strategy is model-free and adaptive.
This work was partly funded via IDCORE, the Industrial Doctorate Centre for Offshore Renewable Energy, which trains research engineers whose work in conjunction with sponsoring companies aims to accelerate the deployment of offshore wind, wave and tidal-current technologies
Associated Project(s) ETI-MA2003: Industrial Doctorate Centre for Offshore Renewable Energy (IDCORE)
Associated Dataset(s) EDC0000134: Tidal Energy Site Environmental Conditions Measured During the ReDAPT Tidal Project 2011-2014
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