External Loads, direction, coordinate system

[Carina Spengler]

Hello,

I want to add an external force from the hand to the proximal row. I've been trying using the External Loads Tab in the Inverse Dynamics Tool for a while now. This worked fine, I also got some resulting moments. But I don't know if I do it properly, I would be glad about some examples or some verification.

1) If I choose point force in the external loads edit menu, I'm not sure in which coordinate system the force is applied. Probably it is the local frame of the hand?

2) When associating motion data to my ID results, I can display the green arrows accordingly. Here I don't know if the force gets calculated in the ID in the same direction and same point as it is displayed by the arrows or if it is just a visual representation?

3) In the .XML I chose to express the force from the hand to proximal row. I also changed the force points in x,y,z direction in the .mot file so that their force application point lies between hand and proximal row. To me it seems that I maybe doubled it. I also thought about the force point to be in dependence with the local hand frame. Eventually someone can explain to me, if changing the force points is the correct way to get the exact application point.

I would be very glad, if someone can help me understanding and applying the external forces correctly.

Best regards,
Carina Spengler