change the simulation stop time from a block

I understand you may change the simulation stop time using set-param function. However, I'd like to do the same thing with a block. This way I can make it to a library so that people just take it from library and drop to his/her model. I need to be able to change the stop time which is calcuated by this block. Thanks.

Answer 1

[Ameer Hamza]

You can stop the simulation at any using stop block: https://www.mathworks.com/help/simulink/slref/stopsimulation.html. You can define a condition, and when the condition becomes true, the simulation stops. Note, this method will only allow decreasing the simulation time. If you want to run the simulation, longer than the stop-time, I am not sure whether it is possible.

[madhan ravi]

Golden comments:

Thanks for the reply. As you rightly pointed out, Stop block can only allow decreasing the simulation time. I tried it and simulation stops at the lesser of the two: model stop time and the stop block condition time. Thanks for trying though.

[Ameer Hamza]

I just tried and found that it is possible to change the simulation time (both increase and decrease) from inside the simulink_model using the MATLAB function block. See the attached model. You can try by pasting the following code in a MATLAB function block.

function fcn()

coder.extrinsic('set_param');
coder.extrinsic('gcs');
set_param(gcs, 'StopTime', '5');

This will change the simulation time to 5, despite whatever is set by the user.

[Golden]

Thank you for the reply. I'd like to try it, but I have 2017a version for now. Can you attach a 2017a version of the model. Thanks.

[Ameer Hamza]

The attached model is exported in R2017a.

[Golden]

I got an error running your model:

An error occurred while running the simulation and the simulation was terminated

Caused by:

SubSystem block does not have a parameter named 'StopTime'

Am I missing something?

[Ameer Hamza]

Golden, In the MATLAB function block, try to replace 'gcs' in the last line with the name of your simulink model

set_param('model_name', 'StopTime', '5')

[Golden]

Yes. With the model_name it works.

Is there any way to not need to manually change the model_name every time it is used in a different model? I intend this to be a drop and play block. I know I am asking a lot, but you are the expert. Thanks.

Also, you saw you used coder.extrinsic functions. Does it mean user has to have Simulink coder to be able to run this?

[Ameer Hamza]

No, simulink coder is not needed to use coder.extrinsic.

In my original code, I used gcs to pick up the model name automatically, but it turns out that it will fail in some cases. Replace the code inside the MATLAB function block to

coder.extrinsic('set_param');
coder.extrinsic('bdroot');
set_param(bdroot, 'StopTime', '5');

[Ameer Hamza]

Golden's comment moved here:

here is what I got:

Function 'bdroot' is not supported for code generation. Consider adding coder.extrinsic('bdroot') at the top of the function to bypass code generation.

Function 'MATLAB Function' (#46.87.93), line 5, column 11:

"bdroot"

Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

[Ameer Hamza]

Golden, have you added the line

coder.extrinsic('bdroot');

as I gave in my comment?

[Golden]

it turned out I somehow had extra white spaces in the strings. Now it is good.

A further question: instead of a constant of 5 seconds for example, I have to calculate the stop time in the initialize callback function with the user's inputs in the mask. How do you convert the stop time to a string? The Matlab function num2str definitely is not ok anymore.

Thanks alot.

[Ameer Hamza]

Since your block will just be limited to simulations and it will not be used for code generation, you can add the line

coder.extrinsic('num2str');

and then use num2str in your Simulink code.

[Golden]

Well, i still can't get it to work. Here is the problem: I have Tend initialized in the mask of this block. When running this MATLAB function I got this:

Undefined function or variable 'Tend'.

Function 'VenableBlock2/MATLAB Function' (#58.141.145), line 6, column 39:

"Tend"

Launch diagnostic report.

Component:MATLAB Function | Category:Coder error

[Ameer Hamza]

See the attached file. First, create a parameter in mask and then follow this: https://www.mathworks.com/help/simulink/ug/parameter-arguments-in-matlab-function-block-functions.html to make the parameter visible inside the MATLAB function block.

[Golden]

great. it works. thanks a lot.

[Ameer Hamza]

I am Glad to be of help.