Load-measurement method for floating offshore wind turbines based on a long short-term memory (LSTM) neural network

Complicated loads encountered by floating offshore wind turbines (FOWTs) in real sea conditions are crucial for future optimization of design, but obtaining data on them directly poses a challenge. To address this issue, we applied machine learning techniques to obtain hydrodynamic and aerodynamic loads of FOWTs by measuring platform motion responses and wave-elevation sequences. First, a computational fluid dynamics (CFD) simulation model of the floating platform was established based on the dynamic fluid body interaction technique and overset grid technology. Then, a long short-term memory (LSTM) neural network model was constructed and trained to learn the nonlinear relationship between the waves, platform-motion inputs, and hydrodynamic-load outputs. The optimal model was determined after analyzing the sensitivity of parameters such as sample characteristics, network layers, and neuron numbers. Subsequently, the effectiveness of the hydrodynamic load model was validated under different simulation conditions, and the aerodynamic load calculation was completed based on the D’Alembert principle. Finally, we built a hybrid-scale FOWT model, based on the software in the loop strategy, in which the wind turbine was replaced by an actuation system. Model tests were carried out in a wave basin and the results demonstrated that the root mean square errors of the hydrodynamic and aerodynamic load measurements were 4.20% and 10.68%, respectively.