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    Adaptive control of a wave energy converter simulated in a numerical wave tank


    Davidson, Josh and Genest, Romain and Ringwood, John (2017) Adaptive control of a wave energy converter simulated in a numerical wave tank. Proceedings of the 12th European Wave and Tidal Energy Conference 27th Aug -1st Sept 2017 (747). pp. 1-10. ISSN 2309-1983

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    Abstract

    Energy maximising controllers (EMCs), for wave energy converters (WECs), based on linear models are attractive in terms of simplicity and computation. However, such (Cummins equation) models are normally built around the still water level as an equilibrium point and assume small movement, leading topo or model validity for realistic WEC motions, especially for the large amplitude motions obtained by a well controlled WEC. The method proposed here is to use an adaptive algorithm to estimate the control model in real time, whereby system identification techniques are employed to identify a linear model that is most representative of the actual controlled WEC behaviour. Using exponential forgetting, the linear model can be continuously adapted to remain representative in changing operational conditions. To that end, this paper presents a novel adaptive controller based on a receding horizon pseudo spectral formulation. The paper also demonstrates the implementation of the adaptive controller inside a computational fluid dynamics (CFD)based numerical wave tank (NWT) simulation. The adaptive controller will create the best linear model, representative of the conditions encountered in the fully nonlinear hydrodynamic CFD simulation. Using CFD presents a method to evaluate the adaptive controller within a realistic simulation environment, allowing the convergence and adaptive properties of the present control scheme to be tested. A test case, considering a heaving point absorber, is presented and the adaptive controller is shown to perform well in irregular sea states, absorbing more power than its non-adaptive counterpart. The optimal trajectory calculated by the adaptive model is seen to have a smaller motion and power take-off (PTO)forces, compared to those calculated by the non-adaptive linear control model, due to the increased amount of hydrodynamic resistance estimated by the adaptive model, as identified from the nonlinear viscous CFD simulation.

    Item Type: Article
    Keywords: Adaptive Control; Hydrodynamic Modelling; Wave Energy Conversion; Numerical Wave Tank; OpenFOAMR©;
    Academic Unit: Faculty of Science and Engineering > Electronic Engineering
    Faculty of Science and Engineering > Research Institutes > Centre for Ocean Energy Research
    Item ID: 12465
    Depositing User: Professor John Ringwood
    Date Deposited: 20 Feb 2020 15:28
    Journal or Publication Title: Proceedings of the 12th European Wave and Tidal Energy Conference 27th Aug -1st Sept 2017
    Publisher: European Wave and Tidal Energy Conference 2017
    Refereed: Yes
    URI:

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