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This paper introduces a simulation framework and a corresponding Robust Optimal Control (ROC) for docking Unmanned Underwater Vehicles (UUVs) that leverages Marine Renewable Energy (MRE) for improved autonomy in docking and charging operations. The proposed simulation framework integrates the dynamics of the Wave Energy Converter (WEC), docking station, and UUV within a unified system. Utilizing the WEC-Sim for the hydrodynamic modeling and MoorDyn for mooring dynamics, and in-house UUV dynamics in Simulink, the simulation effectively accounts for complex interactions under dynamic ocean conditions. The ROC docking controller, consisting of a Linear Quadratic Regulator (LQR) and a Sliding Mode Control (SMC), is designed to enhance robustness against environmental disturbances and system uncertainties. This controller utilizes input-output linearization to transform the nonlinear dynamics into a manageable linear form, optimizing docking performance while compensating for disturbances and uncertainties. The combined simulation and control approach is validated under various ocean conditions, demonstrating effective docking precision and energy efficiency. This work lays a foundational platform for future advancements in autonomous marine operations for UUV docking systems integrated with WEC. In addition, this work also demonstrates the feasibility of using MRE to significantly extend the operational duration of UUVs; such a platform will be leveraged for further development of structural health monitoring and fault diagnosis techniques for offshore structures such as WECs and Floating Offshore Wind Turbines.
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Time-Varying Linear Quadratic Gaussian Optimal Control for Three-Degree-of-Freedom Wave Energy Converters
The model of a three-degree-of-freedom Wave Energy Converter can be simplified as a linear time-varying system. In this model, the heave mode parametrically excites the pitch mode, which in turn excites the surge mode. The heave mode, however, is independent to the other two modes when the motion is small. The purpose of this paper is to design a controller to maximize the energy harvested over a receding time horizon. We also want to demonstrate that, with proper design of the control, it is possible to exploit this nonlinear coupling between the modes so as to harvest more energy. The controller selected is the linear quadratic Gaussian optimal control. The prediction of excitation forces is constructed based on the estimation where the estimations are obtained by using extended Kalman Filter. The prediction of excitation force is fed into the controller to compute the time-varying linear quadratic optimal control. Constraints on the WEC motion are accounted for in computing the control. The results show that the energy captured by three-degree-of-freedom Wave Energy Converter is 3:56 times the energy extracted in heave mode only. Higher energy harvesting is demonstrated when the linear time-varying model is used in control design.
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- Award ID(s):
- 1635362
- PAR ID:
- 10059763
- Date Published:
- Journal Name:
- European Wave and Tidal Energy Conference 2017
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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