Is it through an inverse dynamics approach? How reliable/accurate are the joint moments? I want to determine if the plug-in-gait moments can be used as control parameters for a muscle force algorithm.
All joint torques are computed from inverse dynamics.
We don t really know the method use by vicon.
I have found similar results with matrix parametrization or quarternion
I think that the small difference provide from the anthropometric model
If you aim is muscle controlling, why do you not use opensim ?.
Hi Fabien,
Thank you. I am planning to use opensim, but I do not want to rely on only one method and its simplifications and assumptions. I am therefore looking at ways to benchmark the trend predictions of opensim for specific cases in our lab. Would you say it is a valid approach to also use vicon estimates as a benchmarking tool?
Have you also compared joint angles from the plug-in-gait to opensim predictions? I guess in this case it is not only a function of the anthropometric, but more a function of correspondence between the opensim marker and vicon marker set as well as scaling. to test the validity of our opensim model, we plan to use the vicon joint angles as the golden standard in an iterative process to optimise our marker placements. Is this warranted in your opinion?
Your reply is highly appreciated,
Cobus
Hi jacobus
sorry for the delay of my answer.
I never compare plugin gait and opensim model. I should do it.
You have to know that kinematic calculations of these models are different.
opensim considers a-priori definite joint axes and uses an inverse kinematic optimization (Lu, T., & O’connor, J. (1999). Bone position estimation from skin marker co-ordinates using global optimisation with joint constraints. Journal of Biomechanics, 32, 129–134.)
Plugin gait only considers ball joint at all articulation and extracts cardanic angles.
No model can be a golden approach !
regards
Fabien
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