Robust control of heaving wave energy devices in irregular waves

The power absorbed by a wave energy device is depending on the implemented control strategy. Uncertainties in the physical description of the system as well as in the input from irregular waves provide challenges to the control algorithm. In this paper we present a hybrid robust-fuzzy logic controller that allows for addressing the uncertainty in the model as well as the short term tuning of the converter. The converter is comprised of a spherical heaving buoy with a fixed reference, which could be the bottom or a body at rest. The proposed robust controller uses the energy from the Power Take Off (PTO) as input while the Fuzzy Logic (FL) controller portion is used to tune for the short term wave variation. The FL controller action is based on a prediction of the future incoming irregular wave. Simulation results indicate that the proposed hybrid control yields improved energy production, while being robust to modeling errors.