Modified q–[formula omitted] rule for incipient fault detection in industrial processes on analysis of intermittent process variation

Abstract

Incipient faults usually have small impacts on systems. They are easily affected by noise and control effects. Thus, state variables will not deviate from their mean values in a sustained way, but in a fluctuating form. That is, fault samples will return to control limits in some time. I.e., the intermittent process variation occurs. Therefore, there will be lots of missed detection and high detection delay in traditional methods. It even causes the illusion that the system returns to normal. To address this issue, canonical variate residuals are firstly generated. The aim is to capture the system dynamic. Then the modified q–σ rule is proposed, it sets control limits for all variables. And it also monitors the intermittent process variation with fluctuating growth. When tested on a simulated process and a real industrial process, the proposed method is sensitive to the intermittent process variation in incipient faults and has a shorter detection delay.