Introduction
to Simulink
Prof. Dr. Y. Samim
Ünlüsoy
Prof. Dr. Y. Samim ÜNLÜSOY
Mech. Eng. Dept.,
Middle East Technical
ME 513 Vehicle Dynamics
1
University, Ankara
To start Simulink, one has to first
double click on the Matlab icon and
wait for the Matlab window to open.
SIMULINK
Then, click on the “Simulink” icon
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
2
“Simulink Library
Browser”
will open.
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
3
Click on the “File” menu item. Select
“New” and then click on “Model”
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
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A clean window is going to open. New
Simulink model is to be built on this
window.
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
5
Now, let us try to understand the logic behind
Simulink, using a familiar system.
x
Consider a one degree of freedom
mass-spring-damper system.
m
c
k
z
Prof. Dr. Y. Samim Ünlüsoy
+ cx + kx = cz + kz
mx
Introduction to Simulink
6
x
Reorganize the equation of motion
such that the highest derivative term
is expressed in terms of the rest :
m
c
k
z
Prof. Dr. Y. Samim Ünlüsoy
x=−
c
k
c
k
x − x + z + z
m
m
m
m
Introduction to Simulink
7
x=−
c
k
c
k
x − x + z + z
m
m
m
m
x
m
c
SIMULINK
Now start with the acceleration and
integrate to get velocity.
x
k
1
s
z
Simulink/
Continuous/
integrator
Prof. Dr. Y. Samim Ünlüsoy
x
Then integrate velocity to get
displacement.
x
1
s
x
Introduction to Simulink
1
s
x
8
Click on the “integrator”
icon inside “continuous”
selection of the “Simulink
Library Browser” and drag
it into the model window
and leave it there.
Then repeat it for the
second integrator.
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
9
Bring the cursor on the arrowhead of the first
“integrator” icon and drag it to the arrowtail on the
second “integrator” to create the signal line for velocity.
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
10
x=−
c
k
c
k
x − x + z + z
m
m
m
m
SIMULINK
x
It is possible to generate the first
two terms on the right hand side.
m
c
k
x
z
c
x
m
1
s
c
m
Simulink/
Math Operations/
Gain
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
x
x
1
s
k
x
m
k
m
11
x=−
c
k
c
k
x − x + z + z
m
m
m
m
SIMULINK
It is now time to generate the last
two terms on the right hand side.
Simulink/
Sources/
Sine wave
z
x
k
m
Sine wave
z
du/dt
Simulink/
Continuous/
differentiator
Prof. Dr. Y. Samim Ünlüsoy
k
z
m
x
1
s
c
m
c
m
x
1
s
k
m
c
z
m
Introduction to Simulink
12
x=−
c
k
c
k
x − x + z + z
m
m
m
m
SIMULINK
Finally sum all the terms and form
the acceleration signal.
x
Simulink/
Math Operations/
sum
z
Sine wave
+
+-
z
du/dt
Prof. Dr. Y. Samim Ünlüsoy
1
s
-
k
m
x
1
s
x
c
m
k
m
c
m
Introduction to Simulink
13
x=−
c
k
c
k
x − x + z + z
m
m
m
m
SIMULINK
Simulink/
Sources/
constant
A
It is possible to provide different
inputs using a switch.
Simulink/
Signal Routing/
Manual Switch
x
1
s
Constant
z
-
k
m
Manual
Switch
+
+-
z
du/dt
x
1
s
x
c
m
k
m
c
m
Sine wave
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
14
The resulting Simulink model looks like this !
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
15
You can enter parameter values
by clicking on each element.
x
A
1
s
Constant
z
-
k
m
Manual
Switch
+
+-
z
du/dt
x
1
s
x
c
m
k
m
c
m
Sine wave
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
16
A better choice is to write the symbol instead of the
value. The values can be written in an m-script file.
When the m-script file is run, data values will be saved in
the workspace.
x
A
1
s
Constant
z
-
k
m
Manual
Switch
+
+-
z
du/dt
x
1
s
x
c
m
k
m
c
m
Sine wave
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
17
% Data file for sdof.mdl
m=310; % [kg]
C=980; % [N/m/s]
K=15000; % [N/m]
A=0.005; % [m]
f=2; % [Hz]
This is the m-script file to
load data to workspace.
x
A
1
s
Constant
z
-
k
m
Manual
Switch
+
+-
z
du/dt
x
1
s
x
c
m
k
m
c
m
Sine wave
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
18
Now, you would like to
observe the variation of
some variable, say x,
with time. So add an
oscilloscope !
Simulink/
Sinks/
scope
Scope
x
A
1
s
Constant
z
-
k
m
Manual
Switch
+
+-
z
du/dt
x
1
s
x
c
m
k
m
c
m
Sine wave
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
19
So, the final form of the Simulink diagram is :
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
20
First run the m-file for data by writing its name on the
Matlab “Command Window” and pressing enter. Check
that the correct data has been stored in workspace.
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
21
Now to run Simulink for 10 seconds,
click on the arrow head.
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
22
To see the variation of x with time,
double click on the scope.
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
23
The scope window will appear
with the plot of x versus time.
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
24
Click on the binoculars
icon to fit graph to frame
Prof. Dr. Y. Samim Ünlüsoy
Introduction to Simulink
25