Hi all,
I am a beginner with open sim and trying to do an Inverse Dynamic analysis. I used gait 2354 model. I have some questions:
1) It is usual that in biomechanic studies that the moments are expressed in joint coordinate system, which doesn't have perpendicular axis. In which coordinate system the results (moments and forces) are expressed?
2) How are the body coordinate system defined? and how can we change any coordinate system? (based on which landmarks?)
3) I do not exactly understand how we can define external forces for Inverse Dynamics. Usually GRF has three nonzero force components; also, three nonzero moment components which are dependent on the position of the foot. However, we have only a real free vector moment in vertical direction (which can be easily find by a set of equations) and none in the horizontal plane. My question is that which one do we have to put into grf.mot file? the raw output moments of the force plate or the second set that I said?
4) I checked the example tutorial for Inverse dynamics provided in open sim documentation. The GRF is shown to be applied to calcn only, however, we know that the force is applied to toes also (at toe off, for example). Why is this?
5) In the create/Edit external forces in inverse dynamics tool, what are applies torque, applies force, and point columns? I read the documentation again, but I didn't understand it.
Thanks in advance.