Differential fusion of multi-latent-layer temporal features for industrial process fault classification

Industrial process data often possess characteristics such as time series correlation, high dimensionality, and noise. A fault classification method based on the Long Short-Term Memory (LSTM) combined with a Variational Autoencoder (VAE) model (LSTM-VAE) integrates the advantages of LSTM in handling long time series and the VAE in anomaly detection. However, when extracting features, the method mainly focuses on directly using the time series processed through sliding time steps to extract features via the LSTM network, which may lead to neglect or minor influence of abnormal signals during the generation of latent variables from long time series. To address these issues, this paper proposes a Difference Fusion Multi-Latent-Layer Temporal Feature (DFMLF) extraction method. The method calculates the latent variables by weighting the differences of input time series with the hidden states of the LSTM-VAE network to enhance the VAE’s ability to construct features. To further extract features from the generated latent variables that still have temporal characteristics, gated recurrent units are utilized. To prevent information loss, the latent variables before and after modeling are concatenated in dimensions and classified using a Convolutional Neural Networks. This method was evaluated on the Tennessee Eastman process and a real three-phase flow process, comparing it with other six different models. The results validate the effectiveness of the proposed model.