Determination of the principal components for the optimal detection performance of a combined index

In process monitoring, faults might be completely detected by T² or SPE or both of them. However, one index rather than two indices is preferred to monitor a process in practice. The number of principal components (PCs) in principal component analysis (PCA) impacts the fault detection performance obviously. In this paper, we focus on developing a selection criterion for the number of the PCs based on the best detection performance of the combined index and discussing the uncertainty of PCA model through cross validation. The simulation demonstrates that one index has a good detection performance and simplifies the detection system.