Linear filter model representations for integrated process control with repeated adjustments and monitoring

Abstract

a b s t r a c tAn integrated process control (IPC) procedure is a scheme which combines the engineering process control (EPC) and the statistical process control (SPC) procedures for the process where the noise and a special cause are present. The most efficient way of reducing the effect of the noise is to adjust the process by its forecast, which is done by the EPC procedure. The special cause, which produces significant deviations of the process level from the target, can be detected by the monitoring scheme, which is done by the SPC procedure. The effects of special causes can be eliminated by a rectifying action. The performance of the IPC procedure is evaluated in terms of the average run length (ARL) or the expected cost per unit time (ECU). In designing the IPC procedure for practical use, it is essential to derive its properties constituting the ARL or ECU based on the proposed process model. The process is usually assumed as it starts only with noise, and special causes occur at random times afterwards. The special cause is assumed to change the mean as well as all the parameters of the in-control model. The linear filter models for the process level as well as the controller and the observed deviations for the IPC procedure are developed here.

Economic cost models of integrated APC controlled SPC charts

“…The APC is more useful for short-term adjustments and in compensating for process disturbances (Elsayed et al 1995, Tsung and Tsui 2003. The integration of SPC and APC has been known to be better than either of them alone to control the processes (Tsung et al 1998, Jiang and Tsui 2000, Schippers 2001, Duffuaa et al 2004, Tsung et al 2006, Kandananond 2007, Yang and Sheu 2007, Park and Reynolds Jr 2008, Park 2010. In this paper, we develop an economic cost model for the integration of SPC and APC and investigate the effect of the process parameters on the long term expected cost.…”

Estudio de la integración de procedimientos multivariantes para la regulación óptima y monitorización estadística de procesos.

“…Por su parte, Ferrer et al (2000) discuten los beneficios del enfoque integrado APC-SPC en el control de la homogeneidad del calibre de azulejos mediante ajustes en los perfiles de temperaturas del horno de cocción de una empresa azulejera. Más recientemente, Park (2010) sugiere que cuando las causas de variación comunes y especiales que provocan que el proceso se aleje de su nominal, se puedan presentar simultáneamente es necesario que actúe un sistema integrado que el autor también denomina IPC (Integrated Process Control) para controlar el proceso. En su trabajo, divide el proceso en dos partes: el IC (in-control) y OC (outcontrol) que corresponden al proceso en el que no han ocurrido causas especiales y al proceso en el que ha ocurrido alguna causa especial, respectivamente.…”