Error while reducing sample time

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Anuj
Anuj on 23 Jan 2014
Commented: Anuj on 27 Jan 2014
Hi, I have a simulink model containing some algebraic loops.Input to the system is sine wave. When Sample time of this sine wave is 0(by default), simulation runs but I don't get the desired result, So I tried reducing it to 0.001 and when I did that, I got following error-
Simulink cannot solve the algebraic loop containing 'model/Sum' at time 0.001 using the TrustRegion-based algorithm due to one of the following reasons: the model is ill-defined i.e., the system equations do not have a solution; or the nonlinear equation solver failed to converge due to numerical issues. To rule out solver convergence as the cause of this error, either a) switch to LineSearch-based algorithm using set_param('model','AlgebraicLoopSolver','LineSearch') b) reducing the ode45 solver RelTol parameter so that the solver takes smaller time steps. If the error persists in spite of the above changes, then the model is likely ill-defined and requires modification.
What does this mean? and how to get rid of this? Thanks
  9 Comments
Walter Roberson
Walter Roberson on 27 Jan 2014
If you are still getting the same error after giving the above command, then the command did not have any effect: if it had then it would be using LineSearch instead of TrustRegion. Or so I would tend to think.
Why would it happen? If the model has no solutions after the change in parameters. If the only change in parameters was to lower the step size, then the implication would be that the equations have no solutions until a larger time.
You should consider posting your model.
I myself will probably will not be able to find anything wrong with your model as I have never used Simulink and do not have the product to test with. But someone else might have ideas.
Anuj
Anuj on 27 Jan 2014
Thanks for your reply, I'll try to check my model again.

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