Telemark University College
Department of Electrical Engineering, Information Technology and Cybernetics
Simulink Example – Bacteria Population
In this example we will simulate a simple model of a bacteria population in a jar.
The model is as follows:
birth rate=bx
death rate = px2
Then the total rate of change of bacteria population is:
Set b=1/hour and p=0.5 bacteria-hour
We will simulate the number of bacteria in the jar after 1 hour, assuming that initially there are 100 bacteria
present.
Procedure:
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Create the block diagram for the system using “pen & paper”
Start Simulink and create a New Model
Drag in the necessary blocks from the Simulink Library Browser
Configure the different blocks (double-click/right-click depending on what you need). Some blocks
need to be “flipped” (Right-click → Format → Flip Block), while in other blocks you need to set a value
(double-click)
Draw lines between the different blocks using the mouse
Set Simulation Settings (Simulation → Configuration Parameters). The simulation Time (Stop Time)
should be set to 1 (hour)
Use a Scope to see the Simulated Result
You will need the following blocks:
Integrator block
To solve the differential equation. Note! Initial value x0=100
Two Gain blocks
For p (=0.5) and b (=1)
Product block
Sum block
Scope block
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To compute x
Note! One plus (+) must be changed to minus (-)
To show the simulated result. Note! Set to Autoscale
Faculty of Technology, Postboks 203, Kjølnes ring 56, N-3901 Porsgrunn, Norway. Tel: +47 35 57 50 00 Fax: +47 35 57 54 01
Solution:
Block Diagram using “pen and paper”:
Block Diagram in Simulink:
Simulation Result: