Evaluate Simulink model at a given time vector

Hi all,

I have a Simulink model that I run from Matlab and I also use the block "from workspace" to load some data. As you know, I also have to load the time stamp alongside the data I want to use.

Now, I need to enforce Simulink to evaluate the model at the times stated in the block "from workspace". Ideally, this wouldn't require any interpolation in the block "from workspace".

Example:

I load this dummy DATA in my model

DATA = [0, 0;...

1, 10;...

1.3, 18;...

2.1; 21]

where [0, 1, 1.3, 2.1] is the time stamp and [0, 10, 18, 21] is the vector I need. I want Simulink to evaluate the model exactly at times [0, 1, 1.3, 2.1]. It's like a very special variable time step that I would like to enforce.

I hope I have explained clearly what I need.

Thank you everyone in advance!

Answer 1

[Salman Ahmed]

Hi Daniele,

Assuming you wish to produce the simulation outputs at specified times, navigate to the model configuration settings under Data Import/Export option, find "Output Options" in Additional Parameters. Set this parameter to "Produce specified output only". Then you can specify the "Output Times" array for which you want to produce the output.

[Daniele Venanzetti]

Hi Salman,

It's exactly what I was looking for! anyway, it seems that I can't fill in the tab with a variable from the workspace. I have an array "time_vec" in my workspace and if I type "time_vec" in "Output Times", it doesn't read it. It says "Invalid OutputTimes specified in the Configuration Parameters dialog for block diagram".

Maybe I could work it around by setting this parameter programmatically from Matlab. I tried running this line of code:

simOut = sim('SimExample', 'OutputOption', 'SpecifiedOutput', 'OutputTimes', 'time_vec');

Where SimExample is the simulink model.

where time_vec is my double array but when I run it, it says:

'Invalid OutputTimes specified in the Configuration Parameters dialog for block diagram SimExample'.

Do you have an idea of what I am doing wrong?

many thanks!

Answer 2

[Ahmed Mahfouz]

Hello Daniele,

I was having the exact same issue, and the following method worked for me, so you might as well wanna try it.

simOut = sim(model_name, 'OutputOption', 'SpecifiedOutputTimes', 'OutputTimes', sprintf('[%s]', num2str(required_time_vec(:)')));

The reason I used

required_time_vec(:)'

instead of simply

required_time_vec

is that I needed to make sure that the required time vector is passed to the num2str function as a raw vector.