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changing a parameter inside a continuous transfer function during simulation

Asked by Danilo NASCIMENTO on 16 Aug 2015
Latest activity Commented on by Sebastian Castro on 17 Aug 2015
Hey guys, I want to change a parameter of a continuous transfer function during a simulation. Is that possible?

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1 Answer

Answer by Sebastian Castro on 17 Aug 2015

Yes, it is possible.
You can go right into the block and change the parameters mid-simulation. When you hit "OK" in the block, the parameters update.
If you want to do this programmatically, you can do the following -- suppose you are changing a parameter K in a model called myModel:
>> K = 0.2;
>> set_param('myModel','SimulationCommand','update');
- Sebastian

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Well, it can be useful. But this is not what I mean. I don't want to change it manually. For instance, let's suppose I have a continuous transfer function called G(s)=1/(s^2+w0^2), I want to change the parameter w0 at time 0.4 s with a command. This is all in simulink.
I just tried this out by putting the above MATLAB commands inside a MATLAB Function block. Notice a few subtle changes like declaring some functions extrinsic (due to code generation), and also assigning values in the MATLAB base workspace with assignin (a necessary "evil" in this case).
coder.extrinsic('assignin');
coder.extrinsic('set_param');
assignin('base','w0',5);
set_param('untitled','SimulationCommand','update');
This is then placed inside a Triggered Subsystem that triggers when the simulation time exceeds a certain value. For example:
Notice that I am changing the frequency w0 from 1 to 5 at a time of 4 seconds. My results change as follows:
- Sebastian

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