How to change simulink variable from matlab script?

This is a simplified example of the problem I am facing.

What I have:

I have a simulink model (PT1.slx):

And I have a matlab script (control.m):

% clean up

clear

close all

clc

% use simulink

set_param('PT1/K','Value','3');

out=sim('PT1');

% plot results

plot(out.output);

hold on

plot(out.input);

The script, can set the value of a constant, start the model and plot the output, neat!

What I want:

I want to be able to control the value inside my transfer function from my matlab script, for instance this:

What I have tried:

I have found out, that you can't control values like the one circled in red from datalines, for numeric reasons. But I can create a 'variable' for this value and control it from the 'model explorer', but how I can control my variables from a matlab script I do not know.

I have read through the 'set_param' help to see if it could be used for my purposes, but it seems I need a different tool.

I have searched around and found forum entries like

this: https://de.mathworks.com/matlabcentral/answers/426069-setting-simulink-parameter-values-from-script

It talks about how someone can control 'simulink parameters', I don't think that is the same as a 'variable'.

Answer 1

[Benjamin Thompson]

Here is a link to documentation on working with model workspace variables:

https://www.mathworks.com/help/simulink/ug/change-model-workspace-data.html?s_tid=srchtitle_change%20model%20workspace%20data_1

[David Boelke]

Thank you, that was the information I needed.

Answer 2

[Fangjun Jiang]

You can use set_param().

block='PT1/Transfer Fcn';
a=get_param(block,'Denominator')
b=eval(a)
b(2)=1.5
c=mat2str(b)
set_param(block,'Denominator',c);

a =
    '[1 1 0]'
b =
     1     1     0
b =
    1.0000    1.5000         0
c =
    '[1 1.5 0]'

[David Boelke]

That is also a good solution, I used the model workspace, but yours is a good answer, as it is closer to what I used before, thank you.

Answer 3

[David Boelke]

What I used is this:

a=get_param(bdroot,'modelworkspace');
T=1;
a.assignin('T',T);

Then I just replace the number in my simulink with the variable T. It is amazing, I can place variables either in the model workspace or in the base workspace, very cool.