Passive Joint Torque

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Sina Porsa
Posts: 99
Joined: Thu Feb 03, 2011 7:21 pm

Passive Joint Torque

Post by Sina Porsa » Wed Mar 30, 2011 9:23 pm

Hi all,
I would like to add passive joint torques to my model to prevent unusual joint angles during forward dynamics.
I can add the passive torque in older versions (like 2.0.2) but version 2.2 does not recognize the passive torque!! Is it deleted in new versions? If yes, why?
Cheers

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Ayman Habib
Posts: 2251
Joined: Fri Apr 01, 2005 12:24 pm

RE: Passive Joint Torque

Post by Ayman Habib » Mon Apr 04, 2011 10:47 am

Hi Sina,

Version 2.2 comes with an alternative (CoordinateLimitForce) that allows you to apply a force when a coordinate gets close to the end of the Range-of-motion. Please check the documentation on Doxygen. The XML snippet for it is included below, you'd include an instance of these under the <ForceSet> tag in the osim file.

Hope this helps,
-Ayman

<CoordinateLimitForce> <isDisabled>False</isDisabled> <coordinate>Unassigned</coordinate>
<!--Stiffness of the passive limit force when coordinate exceeds upper limit. Note, rotational stiffness expected in N*m/degree.--> <upper_stiffness>1</upper_stiffness>
<!--The upper limit of the coordinate range of motion (rotations in degrees).--> <upper_limit>0</upper_limit>
<!--Stiffness of the passive limit force when coordinate exceeds lower limit. Note, rotational stiffness expected in N*m/degree.--> <lower_stiffness>1</lower_stiffness>
<!--The lower limit of the coordinate range of motion (rotations in degrees).--> <lower_limit>0</lower_limit>
<!--Damping factor on the coordinate's speed applied only when limit is exceeded--> <damping>0.001</damping>
<!--Transition region width in the units of the coordinate (rotations in degrees).Dictates the transition from zero to constant stiffness as coordinate exceeds its limit.--> <transition>0.1</transition> </CoordinateLimitForce>

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Sina Porsa
Posts: 99
Joined: Thu Feb 03, 2011 7:21 pm

RE: Passive Joint Torque

Post by Sina Porsa » Mon Apr 11, 2011 10:21 pm

Thanks Ayman

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