Co-simulation with NLFE Beam

Hi,

 

I am trying to simulate a flexible inverted pendulum on a cart. I have a Matlab simulation that I am trying to verify and compare with the MotionSolve simulation. I am so far attempting to do this in three ways:

 

1. Using a flexible approximation of the pendulum with FEM. For this I made a FEM mesh of the type of beam that I am using (cylindrical beam). However, this method makes the center of mass differ from the rigid center of mass, which gives unwanted vibrations, affecting the accuraccy of the simulation.
2. Using a 1D beam approximation in HyperMesh to create the FEM. This also has some problems, as the response differs a lot from expectations, since the beam does not contain the slope at the beginning and end of the beam elements as a degree of freedom.
3. Finally, I am trying to use an NLFE beam. This one seems to really be an exact match for my model. However, I am trying to verify it by running a co-simulation. But this co-simulation keeps generating the following error:
   ERROR: Failure obtaining VARVAL in user sub SYSFNC!
   ERROR: Error from initialization of user subroutine!
   This error does not occur if I use co-simulation with the same in- and output definitions, but with a Flexbody. I am therefore wondering if it is possible to use co-simulation together with NLFE beam elements.

 

Thanks in advance! If you need more information, or require any of the files I am using, let me know.

 

Kind regards,

Luuk Zwaans