Simulink does messes up step sizes (and doesn't do what I tell it)
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Hi all,
I want to simulate a variable-step size system. The model includes a coupler to a circuit simulator and hence transmits the current step size to the other simulator on each step.
When I run the simulation, I get errors like these on the other side:
ERROR (SIMLNK-57): [Internal] An invalid message was received from the AMS simulator: NextTimeHit must be in future, NextTimeHit=3.875e-07, lastTime=3.875e-07, now=3.875e-07
It seems that simulink makes too small time steps, probably below numerical precision so they arrive as identical numbers on the other side. Alright, so I set:
Min step size: 1000e-12
This should prevent Simulink from making too small steps. But the problem persists!
Now I just remove the coupler and observe the difference in time steps (I export "Clock" to workspace):
plot(diff(simout_time));
This is the result:
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/146153/image.png)
Clearly, there are steps which are below the numerical precision (3.388e-21) although I told Simulink that the minimum step should be 1e-9 !!
How can this be fixed?
PS: Taking a fixed-step solvers works as expected but this is not what I want.
1 comentario
Joachim Kahr
el 5 de Abr. de 2019
Editada: Joachim Kahr
el 5 de Abr. de 2019
Has anyone found a solution to this problem?
I face the same problem and are not sure if this problem is only simulink related or if the communication over the socket leads to this problems.
KR,
Joachim
edit: setting the sample time of the coupler to a fixed step size is kind of a workaround as the min step size of the simulator does not affect the step size inherited from the coupler. anyway, this is a tradeoff between simulation time and accuracy....
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