بسم الله الرحمن الرحيم advanced control lecture three pid controllers 1- action...
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بسم الله الرحمن الرحيم
Advanced ControlLecture three
PID Controllers
1- Action and types (Smith & Corripio: Chapter 5)
2- Reset windup (Smith & Corripio: Chapter 5)
3- Modifications (Smith & Corripio: Chapter 5 and Astrom & Hagglund: Chapter 3)
1Lecturer: M. A. Fanaei Ferdowsi University of Mashhad
PID Control
1. Action of Controller: If the action is not correctly selected, the
controller will not control
• Reverse action (increase/decrease)
In feedback control loop, the
multiplication of Process gain
(Kp), Control valve gain (Kv),
Sensor gain (Km) and Controller
gain (Kc) must be positive.
Reverse action : If Kp Kv Km > 0 → Kc > 0 2
PID Control
• Direct action (increase/increase)
To determine the action of a controller, the engineer must know:
1. The process characteristics
2. The fail-safe action of the control valve
Direct action : If Kp Kv Km < 0 → Kc < 0
3
PID Control
2. Type of PID Controller
• Classic PID:
• Parallel PID:
• Series PID:
dt
tdeKdtte
KteKmtm Dc
I
cc
)()()()(
s
sK
sE
sMsG D
Icc
1
1)(
)()(
1
11
)(
)()(
s
s
sK
sE
sMsG
D
D
Icc
1
111
)(
)()(
s
s
sK
sE
sMsG
D
D
Icc
Range :0.05 to 0.2(0.1)
4
PID Control
5
PID Control
3. Reset Windup
dt
tdeKdtte
KteKmtm Dc
I
cc
)()()()(
6
PID Control
4. Reset Feedback (RFB)
Internal Reset Feedback
Mmin
Mmax
Mmax
Mmin
mM
mMmmM
100max
min
s
sK
s
K
sE
sM
I
Ic
I
c
1
11
1)(
)(
7
PID Control
4. Reset Feedback (RFB)
8
PID Control
4. Reset Feedback (RFB)
External Reset Feedback 9
PID Control
5. Back Calculation
Back-Calculation with internal tracking
Tracking Time ConstantTd < Tt < Ti
Internal tracking signal
sT
e
T
eK
t
s
i
1
10
PID Control
5. Back Calculation
Back-Calculation with external tracking
External tracking signal
11
PID Control
5. Proportional and Derivative Kick
dt
tdeKdtte
KteKmtm Dc
I
cc
)()()()(
yyeycyeybyeWheredt
tdeKdtte
KteKmtm
spspdspp
dDc
I
cpc
,,
)()()()(
Proportional Kick Derivative Kick
Range: 0-1 Range: 0-1, Commonly zero
Two Degrees of Freedom or ISA - PID
12
PID Control
13