Multimode Process Monitoring Based on Switching Autoregressive Dynamic Latent Variable Model

In most industrials, the dynamic characteristics are very common and should be paid enough attention for process control and monitoring purposes. As a high-order Bayesian network model, autoregressive dynamic latent variable (ARDLV) is able to effectively extract both autocorrelations and cross-correlations in data for a dynamic process. However, the operating conditions will be frequently changed in a real production line, which indicates that the measurements cannot be described using a single steady-state model. In this paper, a set of switching ARDLV models are proposed in the probabilistic framework, which extends the original single model to its multimode form. Based on it, a hierarchical fault detection method is developed for process monitoring in the multimode processes. Finally, the proposed method is demonstrated by a numerical example and a real predecarburization unit in an ammonia synthesis process.