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joint location in parent frame
Posted: Sat Oct 14, 2023 4:22 am
by soroosh.b.k
Hello
Bing me a question when I read the model file, Why the knee_r and knee_l joint locations in the parent frame which is the femur frame, are zero in the models? I have been checked "gait2392" and "gait2354"
Please see the attached file.
Best regards
Soroosh
Re: joint location in parent frame
Posted: Sat Oct 14, 2023 9:30 am
by tkuchida
The motion of the knee is defined by a CustomJoint, where "the child body moves with respect to the parent as a function of the generalized coordinates." The SpatialTransform contains the functions that define how the joint moves. For the knee joint, the SimmSpline functions that define the location of the child (knee) frame's origin are defined relative to the femur frame. Note that the SimmSpline for "translation2" is the following:
Code: Select all
<x> -2.0944 -1.22173 -0.523599 -0.349066 -0.174533 0.159149 2.0944</x>
<y> -0.4226 -0.4082 -0.399 -0.3976 -0.3966 -0.395264 -0.396</y>
For example, when knee_angle_r = -2.0944 radians = -120 degrees, the origin of the child frame is located 42.26 cm away from the origin of the parent frame along the -Y axis. More information about these models can be found on the "Gait 2392 and 2354 Models" page in the documentation (
https://simtk-confluence.stanford.edu:8 ... 354+Models) and in the publications listed at the bottom of that page.
Re: joint location in parent frame
Posted: Sun Oct 15, 2023 1:23 am
by soroosh.b.k
Thank you for your clear explanation. I should have searched more before.
Thanks again.