FOSWEC

Then Floating Oscillating Surge Wave Energy Converter (FOSWEC) is a tension leg moored dual flap device. The two flaps operate in close proximity and have significant cross coupling effects, both from hydrodynamics and rigid body motions (Forbush et al., 2020) – thus the making the FOSWEC an excellent platform to study multi-input, multi-output (MIMO) control with applicability for different types of wave energy converters and arrays of wave energy converters.

Floating Oscillating Surge Wave Energy Converter (FOSWEC) being tested at Oregon State University's O.H. Hinsdale Wave Research Laboratory.

The FOSWEC was first developed as part of the WEC-Sim project, and then adapted to perform tests more focused at fundamental dynamics and controls (Coe et al., 2020). In both cases, testing was performed at Oregon State University’s O.H. Hinsdale Wave Research Laboratory. To support real-time control development, a digital twin of the FOSWEC was developed. The FOSWEC currently resides at Oregon State University’s O.H. Hinsdale Wave Research Laboratory is openly available for researchers to access. The real-time control software for the FOSWEC is available on GitHub. The FOSWEC continues to provide an excellent platform for research on mutli-body WECs (Grasberger et al., 2026).

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The floating oscillating surge wave energy converter (FOSWEC) comprises two pitching flaps mounted to a central floating platform. The device has been tested in multiple experimental campaigns at the Oregon State University (OSU) O.H. Hinsdale Wave Research Laboratory (HWRL) Directional Wave Basin (DWB), and a WEC-Sim numerical model has been developed and validated against these data. This study presents a reduced-coordinate model using Multibody for Everybody (M4E) and WecOptTool, enabling accurate and efficient optimization for complex systems. Code-to-code verification against WEC-Sim shows normalized root-mean-square error of approximately 0.02% for the pitch response of both flaps in the small-amplitude wave case, supporting the model’s use in co-design and optimization studies. Using this framework, we demonstrate the capabilities of WecOptTool and M4E by optimizing control performance across a range of wave conditions, controller types, and mass properties.

With a wide variety of wave energy device archetypes currently under consideration, it is a major challenge to ensure that research findings and methods are broadly applicable. In particular, the design and testing of wave energy control systems, a process which includes experimental design, empirical modeling, control design, and performance evaluation, is of interest. This goal motivated the redesign and testing of a floating dual flap wave energy converter. As summarized in this paper, the steps taken in the design, testing, and analysis of the device mirrored those previously demonstrated on a three-degree of freedom point absorber device. The method proposed does not require locking WEC degrees of freedom to develop an excitation model, and presents a more attainable system identification procedure for at-sea deployments. The results show that the methods employed work well for this dual flap device, lending additional support for the broad applicability of the design and testing methods applied here. The aim of this paper is to demonstrate that these models are particularly useful for deducing areas of device design or controller implementation that can be reasonably improved to increase device power capture.

This report describes the testing of a model scale wave energy converter. This device, which uses two aps that pivot about a central platform when excited by waves, has a natural frequency within the range of the waves by which it is excited. The primary goal of this test was to assess the degree to which previously developed modeling, experimentation, and control design methods could be applied to a broad range of wave energy converter designs. Testing was conducted to identify a dynamic model for the impedance and excitation behavior of the device. Using these models, a series of closed loop tests were conducted using a causal impedance matching controller. This report provides a brief description of the results, as well as a summary of the device and ex- perimental design. The results show that the methods applied to this experimental device perform well and should be broadly applicable.

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References

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