From augmentation to translation: Data generation by conditional hierarchical variational autoencoder, enhancing monitoring mooring systems in floating offshore wind turbines

The integrity of mooring systems in floating offshore wind turbines (FOWTs) is crucial, as their degradation alters the platform’s dynamic behavior. A robust machine learning-based health monitoring system that continuously monitors different mooring systems for FOWTs requires data under diverse health, operational, and metocean conditions. To this end, we propose a Conditional Hierarchical Variational Autoencoder (CHVAE) generative model designed for simultaneous data augmentation and domain translation to generate the required data. We train the model to learn the nonlinear relationships between healthy and minority-damaged fairlead tension records from the source mooring system across various sea states. CHVAE generates realistic damaged responses under diverse conditions by leveraging healthy data from the target mooring system. We first assess CHVAE’s ability to augment minority data based on majority distribution, validated on the Modified National Institute of Standards and Technology (MNIST) benchmark dataset. This experiment compares the performance of CHVAE variants with conventional and recent oversampling methods. Second, the open-source software OpenFast simulates the testing and training datasets for simultaneously data augmentation and domain translation on the Offshore Code Comparison Collaboration Continuation (OC4) semi-submersible platform (DeepCwind) FOWT benchmark. OpenFast and CHVAE records are compared through visual, statistical, and behavioral methodologies. Simulations utilize diverse wave seeds to represent excitation randomness and undetected damage severities, assessing CHVAE’s one-to-all capability. Generated records for unobserved sea states and damage severities closely mimic real behavior in downstream binary classification, illustrating the versatility of CHVAE for zero-shot, real-time damage identification.