The document discusses advancements in industrial process control, focusing on PID control technology over the last decade, including performance monitoring, on-demand tuning, and adaptive control. It addresses challenges in the process industry, such as staffing reductions and the need for improved control performance. The conclusion suggests future developments will enhance PID control, especially with wireless devices and better recovery from process saturation.

1. PID Advances in Industrial Control
Terry Blevins
Principal Technologist
DeltaV Future Architecture Team
Austin, TX
Slide 1

2. Agenda
 State of Industrial Process Control as seen by
one manufacturer of distributed control systems
 Advances over the last 10 years
– Performance Monitoring
– On-Demand and Adaptive Tuning
 Current Areas of Research and Development
– PID Recovery From Process Saturation
– PID Control Using Wireless Devices
 Conclusion, Future
2
Slide 2

3. Advances in Control System Design
 Technology has allowed the cost and footprint of
the control system to be reduced while allowing
control functionality to be increased.
3
Slide 3

4. Fieldbus Impact
A variety of fieldbuses and field device have been introduced that
simplify field wiring and allow control to be distributed to the device level
Intranet
Access
Electronic
Marshalling
Wireless
4
Slide 4

5. Electronic Marshalling
Electronic marshalling has simplified field wiring
5
Slide 5

6. The impact of standards
 IEC61804 defines function
blocks for process control
 Supports distribution of control
to field devices.
 Defines the use of measurement
status indicate measure quality
and mode to determine the
source of setpoint and block
output.
 Electronic Device Description
Language(EDDL) enables a
control system to work with any
manufacturer’s device.
 HART, Foundation Fieldbus, and
Profibus devices are consistent
with this standard.
6
Slide 6

7. PID is the Basis For Continuous Process Control
PID is the dominant technology
for feedback control
Single loop and multi-loop PID Advanced control e.g. MPC, Fuzzy
7
Slide 7
>95% of control application Logic < 5% of control application

8. Example of Operator Interface to Control
 The latest UI
technology allows
the plant operator
to do more.
 Graphic displays
and historic trends
allow the operator
to view and
interact with
discrete and
continuous control
 Web technology
allows remote
access to
measurement,
control, and
calculations
8
Slide 8

9. Issues Confronting The Process Industry
 In many cases the staffing at the plant level has been
reduced. Plant support at the corporate level may have been
severely downsized or eliminated.
 Process engineers and instrumentation technicians may not
have sufficient training to fully understand control setup and
tune PID loops for best performance.
 Resources at the plant level may only be sufficient to
address issues that disrupt production.
 The impact of control utilization/performance may not be
monitored, documented and/or effectively communicated to
plant management.
 This is a global issue – Not specific to the control system
manufacturer, commonly encountered in many major plants
located in the US, Europe, Asia Pacific, Middle East.
9
Slide 9

10. Example – Pulp and Paper
 After plant
management saw the
results of this survey,
a team was formed to
address control issues
in a timely fashion.
 The reduction in
variability led to
significant
improvements in plant
throughput and
product quality.
 Two years later the
plant set a new
production record.
10
Slide 10

11. Example - Petrochemical Complex
 Once plant
management became
aware of the low
control utilization,
manpower and
funding were provided
to investigate and
correct the
measurement and
control issues
 Work to improve
control performance
should begin with an
assessment of control
utilization.
11
Slide 11

12. Control System Manufacturer’s Focus
Customer Issues
e.g. Performance
Monitoring
New Technology Control System Product
e.g. Wireless Research and Changes
Device Development
Standards
e.g. IEC61804,
S88
12
Slide 12

13. PERFORMANCE MONITORING
Measurement status and control mode as defined by IEC61804 are key
to performance monitoring
13
Slide 13

14. Performance Monitoring - Example
 Explorer tree allows easy
navigation of control hierarchy
 Overview display summarizes
performance for System, Area,
Units and Modules
 Abnormal Control Conditions
indicated for Problem Loops:
– Control Service Status:
• Incorrect mode
• Limited control output
• Bad/Uncertain input
– Control Performance Status:
• Standard Deviation
• Variability Index
• Oscillation Index
• Tuning Index
 Device and Valve Diagnostics
14
Slide 14

15. Performance Reports - Example
Communication of
Results to Plant
Management
Standard Reports
 Quickly identify
control problems
 Track
performance,
Schedule for
automatic
generation
Customized Reports
 Add production
KPI‟s
15
Slide 15

16. On-Demand Tuning - Example
 One of the most
effective on-demand
tuning technologies is
relay oscillation as
originally developed by
Åstrӧm and Hägglund.
 Allows tuning to be
quickly established
when commissioning
control.
 Tuning rules such as
modified Ziegler
Nichols tuning may be
used to determine the
PID tuning.
16
Slide 16

17. Adaptive Tuning
Allows tuning the process
model to be automatically
established based on:
 Normal setpoint
changes made by the
operator when the PID
is in an automatic
 PID output changes
when the PID is in a
manual mode.
Model switching with re-
centering and interpolation
may be used for process
model identification – see
Intelligent PID Product
Design
17
Slide 17

18. Adaptive Control - Implementation
 To allow the data
used in adaptive
control to be
collected without
communication
skew or jitter,
adaptive control is
implemented
directly in the PID
 Enables adaptive
control to be
utilized even in
high speed control
applications.
18
Slide 18

19. Recovery From Process Saturation
 The recovery of the PID
from process saturation is
critical in many
continuous and batch
applications.
 By utilizing a variable
preload when the PID
PI Control output is limited for an
extended period of time
(process saturation), it is
possible to minimize
setpoint overshoot on
recovery from saturation.
 See conference paper
Improving PID Recovery
from Limit Conditions.
PI Control with Variable Pre-load
19
Slide 19

20. Example - Boiler Outlet Steam Temperature
 If steam generation
exceeds the
attemperator
capacity the boiler
outlet steam
temperature will
exceed the outlet
Standard PID PID w/Variable Pre-load setpoint with the
spray valve fully
open.
 When boiler firing
rate is reduced, the
spray value should
be cut back as the
50% Drop in outlet temperature
steam generation
SP Overshoot drops.
20
Slide 20

21. PID Modifications for Wireless Control
The Challenge – Control Using Wireless
 Transmitter power consumption is minimized by reducing the number
of times the measurement value is communicated.
 Conventional PID execution synchronizes the measurement value
with control action, by over-sampling the measurement by a factor of
2-10X.
 The rule of thumb to minimize control variation is to have feedback
control executed 4X to 10X times faster than the process response
time (process time constant plus process delay).
 The conventional PID design (i.e., difference equation and z-
transform) assumes that a new measurement value is available at
each execution and that control is executed on a periodic basis.
21
Slide 21

22. Conventional Approach – Over
Sampling of Measurement
Process Output
63% of Change O
Time Constant ( )
Deadtime (TD )
Process Input
I
Control Execution
New Measurement Available
22
Slide 22

23. Conventional PID - Impact of Wireless
 The underlying assumption in traditional control design is that the PID
is executed on a periodic basis.
 When the measurement is not updated on a periodic basis, the
calculated reset action may not be appropriate.
 If control action is only executed when a new measurement is
communicated, this could result in a delayed control response to
setpoint changes and feedforward action on measured disturbances.
Conventional PID Design
23
Slide 23

24. *WirelessHART Solution
Window communication is the preferred method of communications
for control applications. A new value will be communicated only if:
 the magnitude of the difference between the new measurement
value and the last communicated measurement value is greater
that a specified trigger value
 or if the time since the last communication exceeds a maximum
update period.
Thus, the measurement is communicated only as often as required
to allow control action to correct for unmeasured disturbances or
response to setpoint changes.
For Windowed mode you must specify an update period, a
maximum update period, and a trigger value.
*HART 7 specification that has been adopted as an international standard,
IEC 62591Ed. 1.0.
24
Slide 24

25. PID Modification for Wireless Control
 To provide the best control for a non-periodic measurement, the PID
must be modified to reflect the reset contribution for the expected
process response since the last measurement update.
 Control execution is set faster than measurement update. This
permits immediate action on setpoint change and update in faceplate.
25
Slide 25

26. PIDPlus Using Wireless Transmitter vs.
Conventional PID and Wired Transmitter
Lambda Tuning ʎ = 1.0
Communication Resolution = 1%
Communication Refresh = 10sec
Control
Setpoint PIDPlus Measurement
PID
PIDPlus
Control Output
PID
Unmeasured
Disturbance
26
Slide 26

27. CONTROL PERFORMANCE DIFFERENCE
 Communications transmissions are reduced by over 96 %
when window communication is utilized.
 The impact of non-periodic measurement updates on
control performance as measured by Integral of Absolute
Error (IAE) is minimized through the PID modifications for
wireless communication.
27
Slide 27

28. PIDPlus - Modified Derivative Action
28
Slide 28

29. PID Performance for Lost Communications
 The Conventional PID provides poor
dynamic response when wireless
communications are lost.
 The PID modified for wireless control
provides improved dynamic response under
these conditions
29
Slide 29

30. Wireless Communication Loss –
During Setpoint Change
Setpoint PIDPlus
Control
Measurement
PID
PIDPlus
Control Output
PID
Communication Loss
30
Slide 30

31. Wireless Communication Loss –
During Process Disturbance
PIDPlus
Setpoint Control
Measurement
PID
PIDPlus
Control Output
PID
Communication Loss
31
Slide 31

32. Installation at Broadley James
 Portable
Hyclone 100
liter disposable
bioreactor
 Rosemount
WirelessHART
gateway and
transmitters for
measurement
and control of
pH and
temperature.
Pressure
monitored
 BioNet is based
on the DeltaV
Control system.
32
Slide 32

33. Broadley James Bioreactor Setup
VSD
VSD Media
37 oC VSD
Inoculums TC TT
41-7 41-7
VSD Glutamine
VSD VSD
Bicarbonate Glucose
Heater
7.0 pH
AY AC AT AT
Splitter AC
41-1 41-1 41-1 41-4s1 41-4s1
0.002 g/L pH Glucose 2.0 g/L
AC AT AT AC
41-2 41-2 41-4s2 41-4s2
DO Glutamine
2.0 g/L
AT AT AT
41-5x1 41-5x2
Bioreactor
41-6
Viable Dead Product
Cells Cells
CO2 MFC LT
41-14
AY Level
Splitter VSD
41-2
O2 MFC
Drain
33
Slide 33 Air MFC

34. Wireless Temperature Loop Test Results
34
Slide 34

35. Wireless pH Loop Test Results
35
Slide 35

36. Separations Research Program, University
of Texas at Austin
 The Separations Research
Program was established at
the J.J. Pickle Research
Campus in 1984
 This cooperative
industry/university program
performs fundamental
research of interest to
chemical, biotechnological,
petroleum refining, gas
processing, pharmaceutical,
and food companies.
 CO2 removal from stack gas
is a focus project for which
WirelessHART transmitters
were installed for pressure
and steam flow control
36
Slide 36

37. Steam Flow To Stripper Heater
37
Slide 37

38. Column Pressure Control
38
Slide 38

39. PC215 On-line Column Pressure Control
 The same
Wired Measurement dynamic control
Used in Control response was
observed for
SP changes
 Original plant
PID tuning
was used for
both wired
and wireless
control
GAIN=2.5
RESET=4
Wireless Measurement RATE=1
Used in Control
Answers Questions
2a & 2b
39
Slide 39

40. Control Performance – Wired vs Wireless
 Comparable control
as measured by IAE
was achieved using
WirelessHART
Measurements and
PIDPlus vs. control
with wired
measurements and
PID.
 The number of
measurement
samples with
WirelessHART vs
Wired transmitter was
reduced by a factor of
10X for flow control
and 6X for pressure
control – accounting
for differences in test
duration.
Test #1 Test #2
40
Slide 40

41. Conclusion
 Control system manufacturers’ research and development
focuses on the need to address customer control issues,
incorporate standards, and adopt new technology.
 A method for improving the recovery of the PID from process
saturation is of interest to the process industry.
 The use of non-periodic measurement updates is a requirement
when PID control is done utilizing wireless transmitters.
 Recent development of PID modifications have been
demonstrated that improve recovery from process saturation and
to allow non-periodic measurement updates from wireless
devices to be used in control. Further research into the
performance provided by these modifications would be of
interest.
 Based on the achieved results it seems very probable that in the
next few years PID control will get smarter and continue to be
the main workhorse of the process industry control.
41
Slide 41