How to integrate a triggered subsystem which contains a third party supplied block with a different fixed sample rate

I have been supplied a third party simulink block with a fixed sample time. It needs to go inside a triggered function block of a different sample time. Is there a way to do this?

Thanks

[Joe Holdsworth]

I should add, trying the above results in this error:

'IDDTest/Triggered Subsystem/Triggered Subsystem/VscIdd1/VscIdd_sfcn' has sample time 0.01. Only constant (inf) or inherited (-1) sample times are allowed in triggered subsystem 'IDDTest/Triggered Subsystem/Triggered Subsystem'.

Answer 1

[Birdman]

To overcome this problem, use Model Referencing. In model referencing, you can specify your model's sampling time separately, in your case 0.01, but please do not forget that its sample time has to be integer multiple of your parent model's sample time. For instance, if you specify your reference model's(in this example, your triggered subsystem) sampling time 0.01, your parent's model sampling time can be 0.001, 0.0001 etc.

Also, solver types have to be the same.

Hope this helps.

https://www.mathworks.com/help/simulink/model-reference.html

[Joe Holdsworth]

Thanks for your answer, I have done this but get the following error...

The Model block 'IDDTest/Triggered Subsystem/Model' referencing model 'IDD_Test' has been improperly placed in the triggered subsystem 'IDDTest/Triggered Subsystem'. The model being referenced must inherit a sample time. Set the Periodic sample time constraint parameter to 'Ensure sample time independent' on the Solver page of the Configuration Parameters for the model 'IDD_Test' and update the diagram to see why it does not inherit a sample time.

To which I then set the time constraint parameter to 'Ensure sample time independent' on the Solver page which results in the following error:

This model will not inherit a sample time because a sample time was explicitly set in block 'IDD_Test/VscIdd/VscIdd_sfcn'.

If this model does not need to inherit a sample time, change the "Sample time constraint" to something other than "Ensure sample time independent" on the Solver tab of the Configuration Parameters dialog.

What am I doinf wrong?

Many Thanks,

Joe.

[Birdman]

Do not place the Model Reference block inside a Triggered Subsystem. The main logic of using a Model Reference block is to execute at regular intervals which is decided by its own sampling time, which will actually do the same thing as Triggered Subsystem does. Therefore, extract it from Triggered Subsystem, place it alone and then retry.

[Joe Holdsworth]

OK thank you, because of the design of the outer model that the third party model is trying to integrate with (and its integration with the real time OS it sits within) it needs to sit in a triggered function block.

The vender of the block has now been able to send me a model with the same base sample time as the rest of model btw, so everything is running at 0.001 time steps, does this offer any other solutions?

[Birdman]

Why don't you simply multiply the output of Referenced Model with zero? For instance, use a Pulse Generator and set its period so that for the first 0.001 seconds, it outputs 1 and for the second 0.001 seconds, it outputs 0 and this pattern goes like that. It will be equivalent to a triggered subsystem numerically, will do the same job.

[Joe Holdsworth]

The Referenced third party model (which has been supplied with a fixed sample time) sits within our models triggered function block, at the moment I need to use it from within the trigged function block unfortunately.

[Birdman]

Then there are two possible solutions at the end:

1-Change your parent model's sampling time to 0.01 to make Triggered Subsystem compatible with your parent model, but this is less likely to happen I guess.

2-Your Triggered Subsystem has to inherit whatever sampling time is used in your parent model but make sure it is valid for it.

Nothing more can be advised at this stage.

[Joe Holdsworth]

Just in case I'm not explaining it very well...

Outer model

3rd party model within function call..

[Joe Holdsworth]

You might not have seen the previous message but the vender has now supplied the model with the same sample time as the base model, however the same error message is generated, it needs to be an inherited sample time...

[Birdman]

One thing to make sure: As long as you use Triggered Subsystem, it has to inherit the sample time of the parent model. Therefore these errors will not go away until you keep using Triggered Subsystem. Since I can not edit your model, that is all I can say.

Answer 2

[Joe Holdsworth]

The solution to this was to move the block outside of the triggered function, although this did require a change of our model to do this.

Thanks for your answers Birdman.

[Birdman]

You are welcome.

I told you to move the block out. :)