Seven-part mechanism in Modelica

Question

I need to model the "seven-part mechanism" in Modelica:

Starting angles are given: Starting from the left side (K5 and K7):

Modellica Model:

• Is it possible to simulate, for example, K5 as one body shape and simply indicate the center of mass?
• Where can I set the starting angles for K5 and K7? In the "revolute2" model, you can set one "phi_start"
• What models should be used for "fixed" B and O? There is this parameter: a position vector from the world frame to frame_b, allowed in the world frame.

edit: I think I can fix the problem with two different angles - I just added another revolver:

My next problem: how to simulate a revolution where K5 and K4 meet? I'm not sure if I should use 2 revolutions? How to model corrections B and O? A is fixed at the origin, but I'm not sure which position vector for B and O.

I always get the error "all connot forces must be unambiguously calculated"

Many thanks for your help.

Answer 1

See an example of Modelica.Mechanics.MultiBody.Examples.Loops.PlanarLoops_analytic, which gives an example of the K4, K5, K6, and K7 mechanism. In this mechanism, set the initial value of the Revolution.

Answer 2

Well, the decisive role in the mechanism is the connection between O and B (a flat four-connected line), which can be solved using, for example, Modelica.Mechanics.MultiBody.Joints.Assemblies.JointRRR, as shown in Modelica.Mechanics.MultiBody.Examples .Loops.PlanarLoops_analytic.

The binary members K5-K4 and K7-K6 are basically the same, and they do not change the degrees of freedom of the aforementioned planar four-channel. Thus, they must be simulated the same way (this means that revolute2 and revolute6 must be created twice in your model) and be connected in the same way as the four four channels after the correct parameterization and initiation.

Optionally, you can model the mechanism using the PlanarMechanics library.