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Discontinuities detected within algebraic loop

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I have the following problem: "_Trouble solving algebraic loop containing 'ABT_ON2' at time 0.511. Stopping simulation. There may be a singularity in the solution. If the model is correct, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances)_" && in the command prompt appears "_Warning: Discontinuities detected within algebraic loop(s), may have trouble solving_"
The strange thing for me is that it starts to run until one signal is switched on. This model consists on a cosimulation with MSC.ADAMS. I have tried to reduce the communication interval but the same problem appears in the same algebraic loop. With the debugger I have seen the three algebraic loops, but no clue is found yet.
Please tell me usual or typical reasons for this problem or a method to look for the cause and fix it.
Thank yo in advance

Accepted Answer

Arnaud Miege
Arnaud Miege on 24 May 2011
Co-simulation can be a source of numerical problems. Here are a few tips for dealing with algebraic loops:
Since you have a discontinuity, you might also want to try to "smoothe", maybe using a low-pass filter, which a frequency set to something higher than the phenomenon you want to capture (e.g. tf(1000,[1 1000]).
HTH,
Arnaud
  1 Comment
Javier Guiterrez
Javier Guiterrez on 24 May 2011
Already solved with the addition of a unit delay block in a proper location.
Thank you

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