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SimTK OpenSim models (.osim) and related example files that are distributed with OpenSim.
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right-hand rule for Rajagopal knee #127

Closed mrrezaie closed 4 years ago

mrrezaie commented 4 years ago

Hi, I posted on the simTK forum but nobody answered. https://simtk.org/plugins/phpBB/viewtopicPhpbb.php?f=773&t=11781&p=33097&start=0&view=

So I ask it here:

Why don't the knees of the Rajagopal model follow the right-hand rule?

Unlike the gait_2392 or Hamner models, the knee flexion values of the Rajagopal model are positive but based on the right-hand rule it should be negative (the same as the above-mentioned models).

Your response would be greatly appreciated. Regards

tkuchida commented 4 years ago

What "right-hand rule" are you referring to? The one I know requires reference frames to be defined such that

All reference frames in OpenSim are right-handed frames.

mrrezaie commented 4 years ago

Hi Tom, https://c-motion.com/v3dwiki/index.php/Right_Hand_Rule Gait_2392 and Hamner models follow this rule but not Rajagopal. This is Hamner: image

And this is Rajagopal: image

tkuchida commented 4 years ago

The knees are defined differently, but this is not a violation of the right-hand rule. Please look at the reference frames in the GUI:

gait2392 Rajagopal
gait2392 Rajagopal

This is not a bug.

mrrezaie commented 4 years ago

Thanks for your reply,

Is that right image the Rajagopal? Because in the latest version of Rajagopal, the knee axes are exactly the same as gait_2392 (X forward, Y upward and Z lateral). Although the axes of both models are the same, but the knee sagittal plane kinematic graphs become vice versa.