Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
This lecture was delivered by Dr. Sakal Japendu for Process Control course at Ambedkar University, Delhi. It includes: Control, Multivariable, Process, Plants, Sensor, Manipulated, Variables, Single-loop, Independent
Typology: Slides
1 / 64
This page cannot be seen from the preview
Don't miss anything!
Process plants ( or complex experiments) have manyvariables that must be controlled. The engineer must1.
Provide the needed sensors
Provide adequate manipulated variables
Decide how the CVs and MVs are paired(linked via the control design)
Fortunately, most of what we learned about single-loopsystems applies, but we need to learn more!
Two control approaches are possible
We will concentrate on
MULTILOOP
L
F
T
A
Multiloop: many
independent PID controllers
Centralized
L
F
T
A
CentralizedController
Some key questions whose answers help us
design a multiloop control system.
All single-loop problems
available MVs?
Let’s start
here to build
understanding
T
A
What is different when we have multiple MVs and CVs?
INTERACTION!!
Definition: A multivariable process has interaction wheninput (manipulated) variables affect more than one output(controlled) variable.
Does this process have interaction?
How can we determine how much interaction exists?
Second way - Empirical modelling (process reaction curve)
0
20
40
60
80
100
120
0.9880.9860.9840.
Time (min)
XD (mol frac)
0
20
40
60
80
100
120
Time (min)
XB (mol frac)
0
20
40
60
80
100
120
x 10
4
Time (min)
R (mol/min)
0
20
40
60
80
100
120
1.56151.56151.56141.56141.56131.
x 10
4
Time (min)
V (mol/min)
Step change to reflux with constant reboiler
docsity.com
How can we determine how much interaction exists?
Second way - Empirical modelling (process reaction curve)
.
s
s
e
s
s
e
s
x
s
s
e
s
s
e
s
x
V
s
R
s
B
V
s
R
s
D
2
3
3
2
3
−
−
−
−
F
R
F
V
x
B
x
D
docsity.com
How can we determine how much interaction exists?
Use the model; if model can be arranged so that it has a
“diagonal” form, no interaction exists.
T
A
Does this CSTR reactorprocess have
interaction?
v
v
11
(s)
21
(s)
12
(s)
22
(s)
d
(s)
d
(s)
D(s)
1
(s)
2
(s)
2
(s)
1
(s)
We will use a block diagram to represent the dynamics of a2x2 process, which involves multivariable control.
G
11
(s)
G
21
(s)
G
12
(s)
G
22
(s)
G
d
(s)
G
d
(s)
Let’s relate the block diagram to a typical physical process.
What are the MVs, CVs, and a disturbance, D?
T
A
Reactor
v
v
Some key questions whose answers help us
design a multiloop control system.
All single-loop problems
Let’s learn how
to answer this
key question
A requirement for a successful design is:
The number of valves
number of CV to be controlled
v
Hot Oil
v
v
L
v
v
v
Hot Oil
F
T
T
T
F
T
T
F
T
T
F
L
v
T
P
F
F
T
OK, but this does not ensure that we can
control the CVs that we want to control!
A system is controllable if its CVs can be maintained at
their set points, in the steady-state, in spite of disturbances
entering the system.
A system is controllable when the matrix of process gains canbe inverted, i.e., when the determinant of K
D
K
K
MV
MV
K
K
K
K
CV
CV
d
d
=
=
1 2
1 2
22
21
12
11
1 2
0 0
Modelfor 2x2system
I am in desperate need of examples
For the autos in the figure
Are they independently controllable?
Does interaction exist?
Connected by spring
For the autos in the figure
Are they independently controllable?
Does interaction exist?
Connected by beam
