Dear Modelica-Users!

We wanted to model a system consisting of a lot of point masses, which are connected among each others by only springs (no joints). Unfortunately we faced the problem, that the rotation of point masses cause errors. We now use bodies instead of point masses to avoid this problem. In turn this leads to a very poor performance (Because of unnecessary equations. We are not interested in the rotation of the particles).

Can anybody give us a hint how to constrain to rotation of point masses without using prismatic joints? Is it possible in Modelica to set the rotation of a point mass equal to the NullRotation? We haven't found further information on the internet :/

Thank you very much for your ideas!!!

Have a nice day!

Sincerely yours, Rene Nölle

Hallo Rene,
could you explain in more details what you are trying to model?
I am not surprise at all that point masses create problems if rotating: they have no inertia defined!
I think your main problem is that you are using incorrect/unrealistic values for the inertia tensor.
Give more info about what you want to achieve and probably I'll be able to help you.
Cheers