Force Plate Data

[Cindy Rom]

Hi,

I'm trying to figure out how to convert a C3D file into a file type supported by OpenSim. I tried using a set of sample data provided by the Vicon Nexus software. I receive the following error while extracting events for the dynamic file:

??? Error using ==> calcFPData at 62
Force Plate 2 == TYPE 0
TOOLBOX CURRENTLY ONLY SUPPORTS TYPE 2 FORCE PLATES
(3 Force & 3 Moment analog channel outputs). i.e.
AMTI, BERTEC


Error in ==> getEvents at 232
FP = calcFPData(itf, C3Dkey, 1);

Error in ==> testWalk at 27
keyDyn = getEvents(c3dFileDynamic, 2, [1 2 3]);

1. Does this toolbox only work for certain type(s) of force plates? If so, which are they? What are "type 2" force plates?

2. Can the MATLAB file(s) be easily modified to specify force plate type?

3. OpenSim does not need the ground reaction forces to create a motion that corresponds with the marker data, correct? Is it possible to somehow zero the force plate data so the marker data can still be extracted, converted, and used in OpenSim?

Still new to OpenSim and the toolbox; I'd appreciate any help or assistance.

Thanks in advance.

[Tim Dorn]

Hi Cindy,

Information on the different types of force plates can be found in the manual (section 4.2). If you don't have a type 2 force plate, you can't use the toolbox to extract GRFs. You can still however get the marker positions from the c3d file - simply use getMarkers.m to get the marker trajectories (note that you have to set up your loadlabels.m file first with the marker labels of your experiment). Try the example provided with the toolbox and that should help you see how the toolbox works.

Cheers,
Tim