Small variation in ankle angle during CMC

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Xiao Hu
Posts: 21
Joined: Fri Jun 26, 2009 9:25 am

Small variation in ankle angle during CMC

Post by Xiao Hu » Mon Apr 14, 2014 6:59 am

Hi,

I am trying to use the Gait2392 model to run CMC. Both the model and the walking data come with the OpenSim 3.2 installation package. I got everything to run appropriately from scaling, IK to RRA. But, the CMC always generated small variation in the ankle angle during stance phase, which RRA does not have (please see the attached figure; the small variation is highlighted.). So, does anyone have any suggestions why this is happening and how to avoid these small variations?

Thank you!

Xiao
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CMC_AnkleVariationStance.png
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jimmy d
Posts: 1375
Joined: Thu Oct 04, 2007 11:51 pm

Re: Small variation in ankle angle during CMC

Post by jimmy d » Mon Apr 14, 2014 2:39 pm

Hi Xiao,

CMC takes time to correct the errors in kinematics and the combination of muscle dynamics taking along time and the foot being very light means that there is some resonance in the kinematics. RRA doesnt have this issue because the actuators don't have delay and the time intervals are much smaller. You can reduce the resonance by making the time windows smaller, but it will only reduce the resonance rather than get rid of it all together.

Hope that helps,
-james
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