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I tried to simulate a simple model consisting of two inertias and a clutch.
At the beginning the clutch is open and one of the inertias is rotating while the other one is not.
After the clutch is closed both inertias should rotate.

Code:


model SimpleClutchExample "one clutch example"
  Modelica.Mechanics.Rotational.Components.Clutch clutch1(peak=1, fn_max=50, locked(fixed=true, start=false));
  Modelica.Blocks.Sources.Ramp ramp(startTime=1, duration=1);
  Modelica.Mechanics.Rotational.Components.Inertia inertia1(J=1, phi(fixed=true, start=0), w(fixed=true, start=10));
  Modelica.Mechanics.Rotational.Components.Inertia inertia2(J=1, phi(fixed=true, start=0), w(fixed=true, start=0));
equation
  connect(inertia1.flange_b,clutch1.flange_a);
  connect(clutch1.flange_b,inertia2.flange_a);
  connect(ramp.y,clutch1.f_normalized);
end SimpleClutchExample;

I simulated the model with a Demo-Version of Dymola 7.4 FD01 and the results of the simulation are as expected.
http://nsa27.casimages.com/img/2011/07/20/110720121832370682.png

If the model is simulated with OpenModelica 1.7.0, both inertias start with the same angular velocity:
http://nsa28.casimages.com/img/2011/07/20/110720122024763284.png

Obviously there is a problem with the initial conditions of the model.

Do I have to specify any additional parameters or is it a problem of OpenModelica 1.7.0?


kind regards

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