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View Full Version : Solution: Strange force plate data in Vicon



gstanczak19
12-23-2008, 03:44 AM
Thanks all for your input regarding strange force plate data in Vicon. I
failed to mention that the forces which would appear wild and outside of the
force platform graphic in workspace, only appeared when there was no
activity on the actual plates. Immediately once a substantial force was
applied, the force in workspace would revert to a normal looking vector,
within the bounds of the force plate graphic.

What I did not notice was that the force vectors in workspace were larger
than they were normally. I would have known that some force calibrations
were incorrect. While calibration constants were one of the first things I
checked, I did not know that there is also a "general scale" in
Workstation. The calibration values I had were for when the general scale
was set to 1. In my case, the general scaled somehow got changed larger.
Error in moment and center of pressure calculations, when only noise was
present on the channel (ie., no actual forces on the plates) were
exaggerated, allowing wildly varying, small forces (1 or 2 pixels long) to
appear anywhere in the reconstruction zone in the workspace.

Some of you mentioned a threshold value being too low, but I was only able
to find this setting in Polygon, not in Workstation. That is what lead me
to the fix though.

Thanks again for all of your input,

Greg