I have been using the version 3.1 to model some gait data. I was previously using VICON workstation to export C3D and in particular the raw analog data for my force plates. I scripted the environment based on the UniMiami model, and all was working well. However now we have updated our lab to the latest VICON system and NEXUS software. This software package automatically converts the raw analog into forces, moments, and COP datum (extremely annoying). I have tried to re-write my environment file, loosely based on the GaitVaughan model. I have got to the point were inverse dynamic analysis runs, but the force plate data is not correct.
It would be greatly appreciated if you could point me in the right direction.
I have not had time to look at your model, but it should be pretty easy to import the data on this format. The steps are roughly the following:
If the force plate is not already there, create it as a dummy segment without any mass. The fix all its rotations so that it basically acts as a massless point.
Create an interpolation driver to drive the xyz positions of the dummy force plate to the CoP coming from Vicon.
Read the force vector into an interpolation function.
Create an AnyForce3D and set its value equal to the interpolation function and its target to be the force platform.
The force is now applied to a massless segment (the force plate) and this segment moves constantlyu to the CoP. The final step is to create an AnyReacForce between the force plate and the foot to make sure the forces are transmitted from the force plate to the foot.
Yes its working well now. If you keep it simple and stick to John’s suggestions then you’ll be fine. Just make sure you have the appropriate files fro COP, force and moment.