This document discusses advanced functionality for process control systems, including measuring and monitoring process variability, configuring PID loops, and detecting abnormal conditions. It proposes calculating standard deviation and other statistical measures at the fieldbus device level to improve monitoring. Methods are presented for distributed control that move tuning and auto-tuning capabilities into field devices in order to overcome limitations of centralized control architectures.

1. Advanced Functionality

2. Agenda
 Process Variability
 Commissioning PID
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27-Jun-01, Slide 2

3. Impact of Reduced
Process Variability
Hard Spec. Operating Operating Average Shift
Limit Average
Feedstock and Scrap Cost
Productivity
Product Quality
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27-Jun-01, Slide 3

4. Statistical Process Monitoring
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27-Jun-01, Slide 4

5. Statistical Process Monitoring
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27-Jun-01, Slide 5

6. Measurement of Process Variability *
Process
Value
Time
“Capability” “Total”: All Data
Only Random Including Short
or Short Term and Long Term
Variability Variability
Reference: ‘Achieving Workd Class Manufacturing through
Process Control’ by Joseph Shunta, Dupont, 1995*
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27-Jun-01, Slide 6

7. Variability Indicators May be Added To
Fieldbus Devices
(X -X) (Xi - Xi -1 )
n n
2 2
i
Stot = i =1
Scap = i =2
n -1 2 (n -1)
Total and Capability
Standard Deviation is
Calculated by I/O and
Control Blocks
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27-Jun-01, Slide 7

8. Calculation Should be Done at The
Fieldbus Device
2.5
Stot
2
1.5
1
0.5 SPI
SPID
SLQ
0
0 1 2 3 4 5
Ratio of process time constant to sample
time
 /T S
Source: World Class Manufacturing Through Process Control
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27-Jun-01, Slide 8

9. Block Parameters for Total and Capability Standard
Deviation
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27-Jun-01, Slide 9

10. Detecting Abnormal
Conditions in Input Blocks
Status Indicates: Quality (Good, Uncertain, Bad)
Reason (Device Failure, Sensor Failure, etc.)
Limit (not limited, high limited, Low Limited)
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Emerson Confidential
27-Jun-01, Slide 10

11. Detecting Abnormal Conditions in
Output Blocks
Status Indicates: Quality (Good, Uncertain, Bad)
Reason (Device Failure, Sensor Failure, etc.)
Limit (not limited, high limited, Low Limited)
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Emerson Confidential
27-Jun-01, Slide 11

12. Detecting That Control is Limited by
Downstream Conditions
Status Indicates: Quality (Good, Uncertain, Bad)
Reason (Device Failure, Sensor Failure, etc.)
Limit (not limited, high limited, Low Limited)
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27-Jun-01, Slide 12

13. Detecting Incorrect Mode of
Operation
Mode Attribute: Target (Operator Requested Mode)
Actual (Mode of operation)
Normal (The designed Mode)
Permitted( Modes that may be selected)
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27-Jun-01, Slide 13

14. Host May Utilize Mode, Status and
Statistics
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27-Jun-01, Slide 14

15. Agenda
 Process Variability
 Commissioning PID
[File Name or Event]
Emerson Confidential
27-Jun-01, Slide 15

16. Structuring Control For A
Distributed Environment
Traditional,
Centralized Distributed
Approach Approach
Control &
Autotunin
g
Limited Sample Rate,
Delay/Variation
introduced by
Communications /control &
Autotuning
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27-Jun-01, Slide 16

17. Application Used For Tuning in
Field Device
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27-Jun-01, Slide 17