Different sample time in Simulink model (R2017b)

Hey guys,

I have an Simulink-Model where i simulate an BLDC Motor. In this Simulation i divided the subsystems in "Software" and "Hardware" parts. At the moment the simulation runs with a sample time of 5e-5. Now I would like to run the Software part with 5e-5 and the Hardware with 5e-6. In the solver settings should be the 5e-6 as the "overall" sample time. I tried to made the changed the subsystems to "atomic" so i can enter a different sample time. But this didn´t work for me. The Motor-Model is build in Laplace form. When i wanted to start the simulation Simulink didn´t liked the Transfer Fcns. So I changed them to Discrete Transfer Fcns. So I fixed this problem... but then other problems appeared. Alle of them are problems with algeabric loops.

So where is my mistake? The simulation works fine with the old sample time for the whole system.

Answer 1

[Sabin]

Using different sample times in different parts of the model should not be a problem, rate transitions can be used between different rates. Without a model is difficult to tell what the problem is. The way we break algebraic loops is important as that might change the dynamics of the system in a negative way. Check this page for some advice in breaking algebraic loops:

https://blogs.mathworks.com/simulink/2015/07/18/why-you-should-never-break-an-algebraic-loop-with-with-a-memory-block/