Make FMU parameters tunable when importing

[fajansen]

With the FMIKit FMU importer, parameters of the FMU can only be changed at the beginning of the simulation. With the Mathworks FMU importer (tested with 2019b), the FMU parameters are tunable and can be changed during runtime.

[fajansen]

Documentation about tunable parameters:
https://www.mathworks.com/help/simulink/ug/using-tunable-parameters.html
Documentation for dashboard (uses tunable parameters):
https://www.mathworks.com/help/simulink/ug/tune-and-visualize-your-model-with-dashboard-blocks.html
Support by Matlab FMU Import: https://www.mathworks.com/help/simulink/ug/work-with-fmi-in-simulink.html
Example with FMU import and GUI by mail, as I can't attach files.

[t-sommer]

Example with FMU import and GUI by mail, as I can't attach files.

You have to ZIP them or append .zip to the filename of an FMU.

[t-sommer]

It should be possible to expose tunable parameters as S-Function Run-Time Parameters.

[fajansen]

Any news on this topic? We really need this.

[fajansen]

Any update?

[t-sommer]

I've created a prototype (443d57f) based on fmikit_demo_BouncingBall that makes parameter e a tunable dialog parameter.

Pros:

• allows changing the parameters at runtime

Cons:

• would replace workspace variables as start values for tunable parameters

[t-sommer]

Another (and probably more robust) approach would be to simply add the tunable parameters as discrete inputs, leveraging the existing infrastructure.

[fajansen]

Would you expose all tunable parameters as discrete inputs or just a few selected by the user? The downside of this approach is that you have to create lots of "constant" blocks and connect them to the right inputs. This might also have a performance impact. Parameters are only written when changed, inputs every timestep.

[t-sommer]

Would you expose all tunable parameters as discrete inputs or just a few selected by the user?

No. These inputs would have to be added individually, like the output ports.

The downside of this approach is that you have to create lots of "constant" blocks and connect them to the right inputs. This might also have a performance impact.

We could keep track of the previous value and only set it, when it has changed.

[fajansen]

This would work nicely for my use case.
If it's only for a handful of variables, the performance impact should also be negligible, keeping track of the previous value is just an additional error source.

[sloghavi68]

@t-sommer I want to test the new tunable parameters with the 3.0 alpha. What do I need to do to make a parameter tunable? Do I have to select it as an input? I noticed that not all parameters have the input option available. Would you mind commenting on what is required for a parameter for it to be available to be defined as a tunable parameter?

[t-sommer]

I noticed that not all parameters have the input option available.

Only tunable parameters can be exposed as block inputs.