Issue with sending GRF data to the external function


I am trying to send Ground Reaction Force data to my external Python code for a separate calculation. I am using the code as shown in the attached image. However, I am getting an error which I also attached here as an image.

If I replace the GRFR in the code with a number, then the model loads successfully. It seems like GRFR is not ready when it is required for the first time. Is there a work around for this issue?

Any advice to overcome this problem is highly appreciate.

Best regards


Hi Jeevan,

What you are trying to do will not be possible. You want to define F in AnyForce using Assistance function that should use the predicted GRF value (which is also an output of the simulation). That is, F = f(GRF). Since, GRF is a simulation output, it won't be available until the current step of the inverse dynamics analysis is completed. Whereas, the external force, F must be ready before the computation of the current step.

What you can do is use the value of GRF from the previous step. I suppose you are writing the GRF values in some file? You should be able to take the value from the previous time step from that file.

I hope this helps.

Best regards,

Hi Dave,

I tried the way you mentioned above, and it worked.


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