muscle singularity problem
Posted: Mon Oct 11, 2010 2:32 am
Hi,
I am using the upper extremity model to calculate the muscle Jacobian (muscle moment arms) and kinematic Jacobian (hand velocity/joint velocity relationship) for given poses via the API. I have problems when I set the "shoulder_elv" coordinate to zero, since this puts the arm into a singular position (the elv_angle does not produce any model movement).
In this position, the muscle moment arms are returned as being tiny or zero. Interestingly, when calculating the kinematic Jacobian, the singularity does not appear to effect its values (although it should!). Is there a way around this? I am using the computeMomentArm() function to find moment arms.
FYI I am using the SimbodyEngine's getVelocity() and getAngularVelocity() functions to construct the kinematic Jacobian.
Thanks
Marc
I am using the upper extremity model to calculate the muscle Jacobian (muscle moment arms) and kinematic Jacobian (hand velocity/joint velocity relationship) for given poses via the API. I have problems when I set the "shoulder_elv" coordinate to zero, since this puts the arm into a singular position (the elv_angle does not produce any model movement).
In this position, the muscle moment arms are returned as being tiny or zero. Interestingly, when calculating the kinematic Jacobian, the singularity does not appear to effect its values (although it should!). Is there a way around this? I am using the computeMomentArm() function to find moment arms.
FYI I am using the SimbodyEngine's getVelocity() and getAngularVelocity() functions to construct the kinematic Jacobian.
Thanks
Marc