Simulink SImulation Inputs and Model Variables

I want to run a model for different input parameters, using an arraySimulink.SimulaitonInput Objects.

In the StopFcn of the Model I want to read some of the model parameters and variables set by the simulink.SimulationInput objects.

To access the parameters I can call

get_param(gcs,'Parameter')

to get the value of the parameter as set by the Simulink.SimulationInput object.

However to access variables of the model I would need to do:

mdlWks = get_param(gcs,'ModelWorkspace');
Variable = getVariable(mdlWks,'Variable');

This however only gives me the default version of the value for Variable. I waat the current set value of Variable though. Is there an alternative get_var function or something that can do this?

Answer 1

[Paul]

Instead of using the StopFcn, maybe you can use setPostSimFcn functionality

[Florian Rössing]

Thanks for your answer. From I read the documentation, the post sim function only has access to the simulation output object. From where I think I cant access the variables.

[Paul]

The documentation, at least in 2022a, is ... less than clear. Anyway, here's an example.

I have a simulaion 'untitled' that uses one variable, "theConstant." Illusturate functionality to pass the simIn.Variables to the output of the sim command.

Create simIn

simIn = Simulink.SimulationInput('untitled');

Set theConstant in simIn. Use the model workspace

simIn = setVariable(simIn,'theConstant',5,'Workspace','untitled');
simIn.Variables

ans =

Variable with properties:

Name: 'theConstant'

Value: 5

Workspace: 'untitled'

Description: ""

Set the post sim function using an anonymous function. Use simIn.Variables as the input to simpostfunc

simIn = setPostSimFcn(simIn,@(simout) simpostfunc(simIn.Variables));

Run the simulation and verify that simIn variables are copied to the sim output via simpostfunc

y = sim(simIn);
y

y =

Simulink.SimulationOutput:

simvars: [1x1 Simulink.Simulation.Variable]

SimulationMetadata: [1x1 Simulink.SimulationMetadata]

ErrorMessage: [0x0 char]

y.simvars

ans =

Variable with properties:

Name: 'theConstant'

Value: 5

Workspace: 'untitled'

Description: ""

function newout = simpostfunc(simvariables)
% simple function to echo the simIn variables to the the simulation output

newout.simvars = simvariables;

end

[Florian Rössing]

I see what you are doing. But that does not solve the problem. You hand the data over directly at the beginning of the simulation. My case now is, i have an array of simIn objects with variable 'a' running 1 through 5, and i want to have the corresponding value of a available at the end of every of the five simulations.Your approach would make the array of sim in objects available in the PostSimFcn, without knowldege of which of them I need.

[Paul]

Each element of the simIn array has its own PostSimFcn. Here is code that binds a unique PostSimFcn to each element, storing the the variable used for each run:

for ii = 1:5
    simIn(ii) = Simulink.SimulationInput('untitled');
    simIn(ii) = setVariable(simIn(ii),'theConstant',ii,'Workspace','untitled');
    simIn(ii) = setPostSimFcn(simIn(ii),@(simout) simpostfunc(simIn(ii).Variables));
end

y = sim(simIn);

y

y.simvars

y =

1x5 Simulink.SimulationOutput array

ans =

Variable with properties:

Name: 'theConstant'

Value: 1

Workspace: 'untitled'

Description: ""

ans =

Variable with properties:

Name: 'theConstant'

Value: 2

Workspace: 'untitled'

Description: ""

ans =

Variable with properties:

Name: 'theConstant'

Value: 3

Workspace: 'untitled'

Description: ""

ans =

Variable with properties:

Name: 'theConstant'

Value: 4

Workspace: 'untitled'

Description: ""

ans =

Variable with properties:

Name: 'theConstant'

Value: 5

Workspace: 'untitled'

Description: ""

As expected, y is a 5-element array of Simulink.SimulationOutput objects, and each element of y contains the value of theConstant that was used in the simulation that generated that element of y.

[Florian Rössing]

Thanks. This would be a solution to the problem. But maybe the problem then was, that my requiremnt would have been to not build any loop or additional structrue around this. Instead of your approach I can just run all simulations and then pass the array of inputs and the array of outputs to a function that handles both.

[Paul]

Well, you could just as easily do that. But the original qeustion started with using using the StopFcn, so I thought you wanted to use automatic callback functionality. Either way, sounds like you have a path forward.

[Paul]

I just realized that the code I posted will overwrite output data in output of sim. The corrections would be pass the sim output into the post sim function, modify it, and return it.

simIn(ii) = setPostSimFcn(simIn(ii),@(simout) simpostfunc(out,simIn(ii).Variables));

function out = simpostfunc(out,simvariables)
% simple function to echo the simIn variables to the the simulation output
out.simvars = simvariables;
end