The Residual T2 Control Chart of the Multivariate Heteroskedasticity Process withTrend Patterns

摘要

Statistical process control(SPC) is widely used toimprove the product quality. The quality of a product can beattributed to several correlated quality characteristics, all ofwhich need to be controlled and monitored simultaneously.Linear trends in processes are usually due to some type ofprocess decay, such as the wearing out of a tool, where there isoften heteroskedasticity. In this paper, the models of theresiduals of the process with heteroskedasticity are fitted usingGlejser test method which can test the increasing or decreasingheteroskedasticity of the process, which can distinguish threekinds of variables in the processes. Then, the identicallyindependent random residuals after eliminating the lineartrend and heteroskedasticity can be controlled by themultivariate T2 control chart. At the end, the axis diameterand surface roughness in the tool wear process are analyzedwith the residual T2 control chart proposed.