Download - 3P04 Tutorial 7 SingleLoop 2008
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
1/19
Chemical Engineering 3P04
Process Control
Tutorial # 7
Learning goals
1. Experience with a single-loop controller
2. Answering some questions from PC-Education
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
2/19
An Introductory Experience with Feedback Control
We use many feedback controllers for a typical process
Each controller has one measurement and onemanipulated variable
Feed
Methane
Ethane (LK)
Propane
ButanePentane
Vapor
product
Liquid
product
Process
fluid
Steam
FC-1
F2 F3
T1 T2
T3
T5
TC-6 PC-1
LC-1
AC-1
L. Key
PAH
LAL
LAH
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
3/19
control display
and computer
A
v1
v2
4-20 mA
4-20 mA3-15 psi
T
Heating medium
Product
composition
An Introductory Experience with Feedback Control
Lets look at one example feedback loop
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
4/19
A
v1
v23-15 psi
T
Heating medium
Product
composition
An Introductory Experience with Feedback Control
Our first task is to learn about the dynamics. Wecan apply the process reaction curve experiment.
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
5/19
0 10 20 30 40 50 60 70 80 90 100-0.5
0
0.5
1
1.5
2
DYNAMIC SIMULATION, Sloop plots deviation variables
Time
ControlledVariable
0 10 20 30 40 50 60 70 80 90 1000
0.5
1
1.5
Time
ManipulatedVariab
le
%open
Molefraction
minute
An Introductory Experience with Feedback Control
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
6/19
An Introductory Experience with Feedback Control
Observations from the experiment.
An increase in valve opening increases the
concentration. The process gain is positive. Time to steady-state is about 25 minutes.
Dead time is about 6 minutes and time constantis about 6 minutes.
The process is stable and overdamped.
The measurement has noise
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
7/19
A
v1
v23-15 psi
T
Heating medium
Product
composition
An Introductory Experience with Feedback Control
The computer has a defined algorithm using the feedback
measurement to determine the next value of themanipulated variable
Calculations are done every 1/3 second
The engineer enters the appropriate parameters
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
8/19
0 10 20 30 40 50 60 70 80 90 100-0.5
0
0.5
1
1.5
S-LOOP plots deviation variables (IAE = 108.3894)
Time
ControlledVariable
0 10 20 30 40 50 60 70 80 90 100
-1
-0.5
0
0.5
1
Time
ManipulatedVariab
le
%open
M
olefraction
minuteKC = 0(Controller off)
An Introductory Experience with Feedback Control
Parameter sets the
aggressiveness
of the controller.
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
9/19
0 10 20 30 40 50 60 70 80 90 100-0.2
0
0.2
0.4
0.6
0.8
1
1.2 S-LOOP plots deviation variables (IAE = 30.8484)
Time
C
ontrolledVariable
0 10 20 30 40 50 60 70 80 90 100
-1.5
-1
-0.5
0
0.5
Time
ManipulatedVariable
%open
M
olefraction
minuteKC = 0.3
Parameter sets the
aggressiveness
of the controller.
An Introductory Experience with Feedback Control
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
10/19
0 10 20 30 40 50 60 70 80 90 100-0.4
-0.2
0
0.2
0.4
0.6
0.8
1
S-LOOP plots deviation variables (IAE = 17.0748)
Time
ControlledVariable
0 10 20 30 40 50 60 70 80 90 100
-2
-1.5
-1
-0.5
0
0.5
Time
ManipulatedVariab
le
%open
M
olefraction
minuteKC = 0.8
Parameter sets the
aggressiveness
of the controller.
An Introductory Experience with Feedback Control
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
11/19
0 10 20 30 40 50 60 70 80 90 100-1
-0.5
0
0.5
1
S-LOOP plots deviation variables (IAE = 21.0976)
Time
ControlledVariable
0 10 20 30 40 50 60 70 80 90 100
-2.5
-2
-1.5
-1
-0.5
0
0.5
Time
ManipulatedVariable
%open
M
olefraction
minuteKC = 1.2
Parameter sets the
aggressiveness
of the controller.
An Introductory Experience with Feedback Control
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
12/19
0 10 20 30 40 50 60 70 80 90 100-2
-1
0
1
2
3
S-LOOP plots deviation variables (IAE = 74.5656)
Time
ControlledVariable
0 10 20 30 40 50 60 70 80 90 100-8
-6
-4
-2
0
2
4
Time
ManipulatedVariab
le
%open
M
olefraction
minuteKC = 1.8
Parameter sets the
aggressiveness
of the controller.
An Introductory Experience with Feedback Control
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
13/19
An Introductory Experience with Feedback Control
Observations from the samples of feedbackperformance.
Feedback that is too weak takes a long time tocompensate a disturbance
Feedback that is too strong gives poorbehavior and can result in instability
Feedback can result in underdamped behavior
for a process that is overdamped.
The process dynamics have the dominant effecton control performance.
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
14/19
An Introductory Experience with Feedback Control
Observations from the samples of feedbackperformance.
Even the best behavior is not perfect. Theprocess must be upset before feedback takesaction.
The valve must be moved to a different steady-
state to compensate for a disturbance. We movethe disturbance from the important controlledvariable to the less important manipulatedvariable.
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
15/19
******************************************************************
* S_LOOP: SINGLE LOOP CONTROL SYSTEM ANALYSIS ** MODIFY FEEDBACK PROCESS PARAMETERS, CV(s)/MV(s) = Gp(s) ** ** Kp (taulead(s)+1) exp (- theta(s)) ** Gp(s) = ------------------------------------------------- ** (tau1(s)+1) (tau2(s)+1) (tau3^2(s)+2(tau3)xi(s)+1) ** ** ** Measurement noise can be added to the dynamic simulation *
* (not the frequency response calculations) by setting kn ** greater than 0. ** ** noise standard deviation ~= 1.4 * kn *******************************************************************SELECT THE APPROPRIATE MENU ITEMMODIFY...
PRESENT VALUES1) Process Gain, Kp 1.0000
2) Dead time, theta 5.003) Time Constant, taulead (numerator) 0.004) Time Constant, tau1 (lag) 2.005) Time Constant, tau2 5.006) Time Constant, tau3 0.007) Damping Coef., xi 1.00
8) measurement noise magnitude, kn 0.059) Return to main menuEnter the desired selection:
S_LOOP parameters for this example
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
16/19
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
17/19
************************************************************** S_LOOP: SINGLE LOOP CONTROL SYSTEM ANALYSIS ** MODIFY PID CONTROLLER TUNING CONSTANTS ** /t ** MV(t) = Kc ( E(t) + (1/TI)| E(t) dt - Td (dCV(t)/dt) )** 0/ ** ** MV(s) = Kc ( E(s) + E(s)/(TI s) - (Td s) CV(s) ) *
* ** ** Hints: 1) Set Kc = 0 to turn controller off ** 2) Set TI = 0 to turn integral mode off ** 3) Units ** Kc has units of 1/Kp ** TI and Td have units of theta and tau **************************************************************SELECT THE APPROPRIATE MENU ITEM
MODIFY...PRESENT VALUES
1) Controller Gain, Kc 1.802) Integral Time, TI 7.003) Derivative Time, Td 0.004) Return to main menu
Enter the desired selection:
S_LOOP parameters for this example
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
18/19
*************************************************************
* S_LOOP: SINGLE LOOP CONTROL SYSTEM DYNAMIC SIMULATION ** ** Hints: 1) All inputs are steps at 5% of total time ** 2) If Entry 5 is non-zero, PID controller ** is turned off ** 3) Select Time step (delta t) to approximate ** a) for the smallest time constant, ** (delta t) / tau = 0.05 ** b) dead time/ (delta t) = integer *
* 4) Usually, (total time) / (time step) < 1000 ** 5) Digital controller exec time integer of ** simulation delta time **************************************************************SELECT THE APPROPRIATE MENU ITEM
PRESENT VALUES1) Total simulation time 99.502) Time step for simulation 0.200
3) Set point change 0.004) Disturbance change 1.305) Process reaction curve MV input 0.00
6) Select continuous/digital controller, currently continuous(Controller executed every simulation time step)
7) Execute dynamic simulation8) Return to main menu
Enter the desired selection:
S_LOOP parameters for this example
-
7/30/2019 3P04 Tutorial 7 SingleLoop 2008
19/19
Reinforcing PID Controller Concepts
Lets Perform the following exercises from PC-Education
Interactive Learning Modules
8.58.9 and 8.13
Tutorial
8.5
(Problems with solutionsit doesnt get any better than this!)