Static Optimization won't run with coordinate limit force

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Jordan Sturdy
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Joined: Fri Sep 22, 2017 8:56 am

Static Optimization won't run with coordinate limit force

Post by Jordan Sturdy » Sat Mar 31, 2018 1:38 pm

I've been working with a model trying to use a coordinate limit force as the constraining element between a backpack and the torso, which currently has a single DOF joint.
I can run RRA with the coordinate limit force enabled, and I let that drive coordinate values for the backpack joint.
When I then try to perform static optimization using the output from RRA, the tool does not progress past these lines if the coordinate limit force is enabled:

Code: Select all

ExternalForce::ExternalForce_1_transformedP
Data source being set to Visual3d_SIMM_grf.mot_transformedP
ExternalForce::ExternalForce_2_transformedP
Data source being set to Visual3d_SIMM_grf.mot_transformedP
Executing the analyses from -0.00019 to 3.2401...
I do not receive a red button indicating an error or any failure from the tool itself.
However, if I disable the coordinate limit force, static optimization will run. I have even put the coordinate limit force in the actuators file, and it willl run as long as the force in the model file is disabled.
I have reserve actuators for every coordinate, and they have limits of +/- infinity. I have raised the optimal force on all the reserve actuators to 100 with no difference in behavior.

I have this problem even when using a "no backpack" trial where the mass of the backpack is set to 0.001 and thus the coordinate limit force should have little effect.

Does anyone have suggestions for how to troubleshoot this issue?


Thank you,

Jordan Sturdy
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User avatar
Jordan Sturdy
Posts: 9
Joined: Fri Sep 22, 2017 8:56 am

Re: Static Optimization won't run with coordinate limit force

Post by Jordan Sturdy » Mon Apr 02, 2018 9:11 am

UPDATE:

This problem seems to be related to the upper stiffness of the coordinate limit force. I didn't remember at the time I posted, but I had issues running RRA until I put in an upper stiffness as well.
If I give it any value, even 1.0, the analyses will run.
I don't understand why this is an issue as the coordinate never tracks into the upper limit range to engage the upper stiffness. Is there a known issue with defining 0 stiffness for one of the coordinate directions?

Jordan
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