how to have an optional bus signal inside a subsystem?

Hello,

I want to create a subsystem that I can reuse in different scenarios (maybe as subsystem reference, not really important).

I would like to pass the signal to this subsystem as a virtual bus.

Inside the subsystem I use the in bus element to get the signals I need from the bus.

Now, since I use this subsystem in different models/configurations there are signals that sometimes are present and sometimes are not present inside the virtual bus, like in the example image below: signal3 is not present inside the bus and so simulink throws the error:

Selected signal 'signal3' in the Bus Element Inport block 'untitledeee/Subsystem1/In Bus Element1' cannot be found in the input bus signal.

I would like to use a default value when I recognize that the input is missing. In matlab functions you can easily do this with optional arguments (link: arguments - defaultValue).

My question is: there is a way to replicate the optional arguments of matlab functions inside a subsystem/reference subsystem/model reference?

There is some suggested workaround?

Answer 1

[Ashutosh Thakur]

Hi Michele,

Simulink does not have a feature for handling optional arguments for the virtual bus in the way MATLAB code can. However, a strategy can be implemented to support this functionality. The following approach can be followed:

• Place a Bus Selector block before the subsystem to identify the signals that could be present in the bus. https://www.mathworks.com/help/simulink/slref/busselector.html.
• Create a custom MATLAB Function block that will check for the missing signals and assign default values to those signals. The output of the Bus Selector block would be the input to this custom block. https://www.mathworks.com/help/simulink/slref/matlabfunction.html.
• Now, after initialising with the default values, leverage a Bus Creator block to reconstruct the bus signals with the new updated values. https://www.mathworks.com/help/simulink/slref/buscreator.html.

The combination of the above-mentioned blocks could help you in reusing your subsystem with optional signal values.

[Michele Oro]

Hi Ashutosh,

thank you for your suggestion. Unfortunately this solution at the core is manual solution while I am looking for something that could handle the situation with some automation.

But you are also right saying that simulink does not have this feature so I will probably have to accept some level of manual action.

Mic