Enhanced Dynamic Dual-Latent Variable Model for Multirate Process Monitoring and Its Industrial Application

Quality-related process monitoring is an important tool to ensure process safety and product quality. However, the existence of process dynamics and multirate sampling makes it difficult to construct an efficient monitoring model. In order to handle process dynamics and multirate sampling, a multirate process monitoring method based on a dynamic dual-latent variable model is proposed. The model involves two sets of latent variables modeled as first-order Markov chains, which are used to capture both quality-related and quality-unrelated dynamic information. In addition, to deal with multiple sampling rates in the process data, the proposed model is combined with a multirate Kalman filtering technique. An expectation-maximization (EM) algorithm is used to estimate the unknown parameters, and a fault detection strategy is developed. The higher fault detection rate of the proposed method is verified by two application studies including a real industrial experiment and the Tennessee Eastman (TE) process.