When working with the Multi-body libraries you might sometimes create a so called algebraic loop. These have to be broken using Modelica.Mechanics.MultiBody.Joints.RevolutePlanarLoopConstraint. This is a suggested solution using it:

Here are some notes that might help in the future:

• Note that I re-arranged the model a bit to make it easier for my-self to see how the model is actually connected. At least for me this makes it a bit easier. (As you can see I have diagonal connection lines, I can accomplish this by first making a connection, then hovering over the green corner points and clicking "-" to remove them)
• My first step was actually to connect this: I.e. I did not connect the entire loop. Instead I added a couple of point masses (btw, in general it is a good idea to have masses in the model to make it numerically easier to handle). That way I can see if I got the coordinates right to begin with: Of course when I simulate it I will not have the correct behavior yet though:
• I then connected the last revolute, and as I realized tat it was an algebraic loop I used the RevolutePlanarLoopConstraint for this.

Hope this helps. I have attached the code.

Attachments:

Test.mo