Unsupervised streaming anomaly detection for instrumented infrastructure

Abstract

SHM) often involves instrumenting structures with distributed sensor networks. These networks typically provide high frequency data describing the spatio-temporal behaviour of the assets. A main objective of SHM is to reason about changes in structures' behaviour using sensor data. We construct a streaming anomaly detection method for data from a railway bridge instrumented with a fibre-optic sensor network. The data exhibits trend over time, which may be partially attributable to environmental factors, calling for temporally adaptive estimation. Exploiting a latent structure present in the data motivates a quantity of interest for anomaly detection. This quantity is estimated sequentially and adaptively using a new formulation of streaming Principal Component Analysis. Anomaly detection for this quantity is then provided using Conformal Prediction. Like all streaming methods, the proposed method has free control parameters which are set using simulations based on bridge data. Experiments demonstrate that this method can operate at the sampling frequency of the data while providing accurate tracking of the target quantity. Further, the anomaly detection is able to detect train passage events. Finally the method reveals a previously unreported cyclic structure present in the data.