00207 óe0c4ec555d6025ec9c052a8a070697
209
Strategies for Statistical Monitoring of Integral Control
Table 3. Performance Measures for EPC/SPC Rules for an Assignable Cause of a Trend in a Process at Observation 251 Based on 2000 Simulations for Control Actions
|
Prediction Error EWMA | |||||
|
PM PriorTo |
MacGregor |
PM With |
CUSUM PM for |
CUSUM PM for | |
|
Shift |
Shift |
PM |
Tracking Signal |
H = 5o and K = lcr H |
= 5 a and K = 2 a |
|
0.05 |
2.55254 |
2.98652 |
2.57546 |
2.71861 |
2.76200 |
|
(0.00513) |
(0.00591) |
(0.00471) |
(0.00471) |
(0.00409) | |
|
*70 Did not |
*1557 Did not |
*1946 Did not | |||
|
Signal |
Signal |
Signal | |||
|
0.10 |
2.54373 |
4.33509 |
2.59306 |
3.26601 |
3.42530 |
|
(0.00505) |
(0.00823) |
(0.00534) |
(0.0093) |
(0.00542) | |
|
6 Did not Signal |
*1614 Did not |
*1970 Did not | |||
|
Signal |
Signal | ||||
|
0.25 |
2.55370 |
13.59206 |
2.58952 |
7.06212 |
8.05101 |
|
(0.00500) |
(0.01644) |
(0.00492) |
(0.00483) |
(0.01154) | |
|
*1633 Did not |
*1992 Did not | ||||
|
Signal |
Signal | ||||
|
0.5 |
2.5551679 |
46.7668 |
2.589698 |
20.89525 |
24.53779 |
|
(0.00509) |
(0.03189) |
(0.00505) |
(0.18635) |
(0.03987) | |
|
*1660 Did not |
*1989 Did not | ||||
|
Signal |
Signal | ||||
|
1.0 |
2.555372 |
179.5869 |
2.60352 |
76.45376 |
90.36461 |
|
(0.004961) |
(0.06273) |
(0.00497) |
(0.73651) |
(0.17908) | |
|
*1669 Did not Signal |
*1984 Did not Signal |
the process, the combined prediction error EWMA and tracking signal scheme is very effective in quickly signaling that a trend of magnitude 0.5 or 1.0 has occurred in the process. For smali trends in the process the ARL is approximately 68 observations.
Strategies for Integration of SPC and EPC
In order to develop comprehensive strategies that control engineers can apply in practice, it is necessary to compare the simulation results presented here for control actions with those presented by the authors in the first paper for the deviation from target. The first observation that can be madÄ™ from both studies is that applying SPC to an existing EPC scheme will help the control engineer detect that an assignable cause has occurred in the process and help reduce overall process variability.
Should the control engineer apply SPC to the deviation from target,
Wyszukiwarka