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.

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.


If the model is simulated with OpenModelica 1.7.0, both inertias start with the same angular velocity:


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