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PID Control for the future
Haruo TAKATSU
Yokogawa Electric Corporation
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Agenda
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Discussion Items
1. Will PID control continue to be used in the future ?
– Market Survey in Japan
2. When and why is derivative action used ?
– Flexibility of PID Control block in DCS
3. What are alternatives ?
– Self-Tuning / Adaptive Control, Internal Model Control
4. What is your favorite tuning method ?
– PID Tuning in our system
5. Do we know everything about PID or are there any
research needs ?
– Introduce Monitoring & Diagnosis
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Needs of PID Control
- SICE Report -
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1400
Applications
Control Technology Survey
90
Ｏ（Others）
80
1200
ＰＷ（Power plant）
70
Ｅ（Engineering）
1000
ＣＲ（Cement and ceramic）
60
ＰＰ（Pulp and paper）
800
Applications
50
ＣＦ（Chemical, fiber,film）
ＰＣ（Petrochemical）
40
600
Ｒ（Refinery）
S(Steel and metal）
30
400
20
200
10
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Control Technologies
Sliding mo de control
Takatsu, H., Itou, T. : Future Needs for Control Theory in Industry
– Report of the Control Technology Survey in Japanese Industry,
IEEE Transaction on Control Systems Technology, 07, 03 pp.298-305 (1999)
Repetitive control
Exact line arizarion
Adaptive c ontrol
Ｈ infinity co ntrol
Observer
Optimal re gulator
Neural net work
Kalman fil ter
Optimizati on
Rule based control
Decoupling PID
Dead time compensation
Fuzzy cont rol
Model pred ictive control
PID auto t uning
I-PD and 2 degrees of
freedom PI D
Gain sched uling
0
0
PID Control Structure
- Derivative Action -
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Control Block in DCS
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PID Control
DV
SV
PID
＋
-
1
100
1
 Td s
Tis
PB
＋
MV
＋
Process
PV
DV
SV ＋
PI-D
-
1
1
＋
Tis -
α
100 MV ＋
PB ＋
Process
PV
Td s
DV
I-PD
1  Tds
1 αTd s
SV＋
-
1
T is
100 MV ＋
PB ＋
＋
-
Process
1  Td s
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PV
PID Alternatives
- Adaptive / Self-Tuning Control
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Self-Tuning Control
Estimated Model
Model Estimation
PID Tuning
PID
parameters
SV
PID Control
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Response Monitoring
MV
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Process
PV
Self-Tuning Control
- Nonlinear Programming Xmax
Xmid
Xbar
Xref
Xmin
In case oscillating and small overshoot,
Xexp
Reflection: Xref = (1+a)Xbar aXmaxIn case No oscillation, slow convergence,
Increase/Decrease P and decrease I.
Decrease
&I.
Expansion:
Xexp=PbXref+(1-b)Xbar
Xmid
Xmid
Xmax
Xcon
Xred
Xmax
Reduction
Contraction:
Xred
In case large overshoot andXcon=
fast convergence,
cXmax+(1-c)Xbar
Xmin
Increase/decrease P & I.
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In case slow oscillation and convergence,
Decrease P and increase I.
PID Alternatives
- IMC Control -
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Internal Model Control
DV
Q(s)
SV +
+
－
-
C(s)
MV
PM(s)
P(s)
-
PV
+
+
PM(s)
－
DV
C(s)
SV +
+
MV
Q(s)
P(s)
PM(s)
+
PV
+
+
－
Controller：C(s)， Internal Model： PM(s)， Process：P(s)
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Internal Model Control
SV +
-
+
Kc(1+TPs)
+
1+λTPs
MV
P(s)
PV
KPe-Lps
1+TPs
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2012.1.6 - 20
PID Tuning Method
- IMC Method -
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PID Tuning
Stable Process
Gain
PI
2τ t d
K (2ε t d )
PID
2τ t d
K (2ε t d )
Reset
td
2
t
τ d
2
Integral Process
Derivative
Reset
Derivative
-
P
1
Kε
-
-
τt d
2τ t d
PI
2
Kε
2ε
-
τ
K=Process Gain,
Gain
PID
td=Dead time
τ=Time Constant
ε=Desired Closed Loop Response
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td
 2ε
2
t
K ( d ε) 2
2
2ε
td
2
td
2
PID Tuning
•
The Advanced Tuning window is for user to perform detail analysis
of each step test data and confirm the final suitable P, I, D
parameters.
most of the important
parameters in loop
configuration
Loop Details Pane
Step Pane
the list of steps captured under the
selected tag and the preview of the
step data
Loops Pane
displays loops grouped
by the “Location”
defined in Loop
Configuration
the main window that user does the
analysis for model and loop
simulation
Advanced Tuning Pane
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PID Tuning is always correct ?
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Research & Development in the Future
- Plant Life Cycle Monitoring & Diagnosis -
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Loop Oscillation & Valve Stiction Dianosis
Valve Stiction Results:
Oscillating Only
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Loop Oscillation & Valve Stiction Diagnosis
Valve Stiction Results:
Oscillating & Sticking
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What is problem after installation ?
•
•
•
•
•
•
Industry has implemented many projects
Shift from project work towards maintenance
Staff is less appealed by maintenance work
Shortage of skilled staff in process control and optimisation
Maintenance can be tedious and time consuming
Too much focus towards Uptime (Online factor)
 Applications do not deliver optimum performance
Reference :
- Recent survey of 20,000 loops performance
Excellent
16%
Acceptable
12%
Fair
28%
Poor
11%
Manual mode
33%
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Thank you for your attention
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