Probabilistic active learning: An online framework for structural health monitoring

•A critical issue for data-based SHM is a lack of descriptive labels for measured data.•For many applications, these labels are costly and/or impractical to obtain.•As a result, conventional supervised learning is not feasible.•A probabilistic framework for investigation and classification of data is suggested.•The algorithm is applied to three datasets in the online setting.•Active learning significantly improves the online classification performance. A novel, probabilistic framework for the classification, investigation and labelling of data is suggested as an online strategy for Structural Health Monitoring (SHM). A critical issue for data-based SHM is a lack of descriptive labels (for measured data), which correspond to the condition of the monitored system. For many applications, these labels are costly and/or impractical to obtain, and as a result, conventional supervised learning is not feasible. This fact forces a dependence on outlier analysis, or one-class classifiers, in practical applications, as a means of damage detection. The model suggested in this work, however, allows for the definition of a multi-class classifier, to aid both damage detection and identification, while using a limited number of the most informative labelled data. The algorithm is applied to three datasets in the online setting; the Z24 bridge data, a machining (acoustic emission) dataset, and measurements from ground vibration aircraft tests. In the experiments, active learning is shown to improve the online classification performance for damage detection and classification.