Balshaw, RyanHeyns, P.S. (Philippus Stephanus)Wilke, Daniel NicolasSchmidt, Stephan2024-08-302024-08-302024-06Balshaw, R., Heyns, P. S., Wilke, D. N., & Schmidt, S. (2024). Temporally-preserving latent variable models: Offline and online training for reconstruction and interpretation of fault data for gearbox condition monitoring. Journal of Dynamics, Monitoring and Diagnostics, 3(2), 156–177. https://doi.org/10.37965/jdmd.2024.534.2833-650X (print)2831-5308 (online)10.37965/jdmd.2024.534http://hdl.handle.net/2263/97939Latent variable models can effectively determine the condition of essential rotating machinery without needing labelled data. These models analyse vibration data via an unsupervised learning strategy. Temporal preservation is necessary to obtain an informative latent manifold for the fault diagnosis task. In a temporal-preserving context, two approaches exist to develop a condition-monitoring methodology: offline and online. For latent variable models, the available training modes are no different. While many traditional methods use offline training, online training can dynamically adjust the latent manifold, possibly leading to better fault signature extraction from the vibration data. This study explores online training using temporal-preserving latent variable models. Within online training, there are two main methods: one focuses on reconstructing data and the other on interpreting the data components. Both are considered to evaluate how they diagnose faults over time. Using two experimental datasets, the study confirms that models from both training modes can detect changes in machinery health and identify faults even under varying conditions. Importantly, the complementarity of offline and online models is emphasised, reassuring their versatility in fault diagnostics. Understanding the implications of the training approach and the available model formulations is crucial for further research in latent variable model-based fault diagnostics.en© The Author(s) 2024. This is an open access article published under the CC BY license (https://creativecommons.org/licenses/by/4.0/).Condition monitoringUnsupervised learningLatent variable modelsTemporal preservationTraining approachesSDG-04: Quality educationSDG-09: Industry, innovation and infrastructureArticle