Statistical Monitoring of the Covariance Matrix in Multivariate Processes: A Literature Review

Abstract

Monitoring several correlated quality characteristics of a process is common in modern manufacturing and service processes. For this purpose, control charts have been developed to detect assignable causes before producing nonconforming products. Although a lot of attention has been paid to monitoring the multivariate process mean, not many control charts are available for monitoring the covariance matrix. This paper presents a comprehensive overview of the literature on control charts for monitoring covariance matrix in multivariate statistical process monitoring (MSPM) framework. It classifies the research that have previously appeared in the literature. We highlight the challenging areas for research and provide some directions for future research.