RRA simulation distortion

Provide easy-to-use, extensible software for modeling, simulating, controlling, and analyzing the neuromusculoskeletal system.
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ajinkya patil
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RRA simulation distortion

Post by ajinkya patil » Tue Mar 08, 2016 8:26 am

Please refer this video and let me know why my skeleton moves slightly up and down during simulation? I have done the mass and COM adjustments also.
https://youtu.be/HvTy0cGNiPk

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jimmy d
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Re: RRA simulation distortion

Post by jimmy d » Tue Mar 08, 2016 11:15 am

Do you have two separate ground reaction forces, applying one to each foot?

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ajinkya patil
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Re: RRA simulation distortion

Post by ajinkya patil » Wed Mar 09, 2016 12:44 am

yes sir, I have 2 seperate GRFS.

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Aaron Godfrey
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Re: RRA simulation distortion

Post by Aaron Godfrey » Wed Mar 09, 2016 9:17 am

I've had odd movements in the y axis myself, but I haven't had GRFs taken into account at any point - just a model (that has an associated motion) that is scaled with the original's motion applied to it. For me, the movement is more of a compression than a drifting as in OP's.

What other possibilities are there?

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ajinkya patil
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Re: RRA simulation distortion

Post by ajinkya patil » Tue Mar 15, 2016 1:09 am

James Dunne, Can you tell us the reason behind this?

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jimmy d
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Re: RRA simulation distortion

Post by jimmy d » Wed Mar 16, 2016 10:37 am

The reason is simple; all of the forces, masses are not in equilibrium. 'Why' can be due to a number of things.

Maybe you didn't apply your external forces correctly, maybe the masses are not correct, maybe the residual actuators are not being applied appropriately.

Have you run Inverse Dynamics and assessed if the joint torques and residuals are what you expect?

I would suggest working through this example. In Part II of the example, you iterate on a Model in RRA to reduce the 'bouncing' and achieve a 'good' simulation.

-j

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