Static optimization and minimum activation

[David André Gomez Romero]

Hello,

I use 'Static Optimization' in order to find joint reaction forces. I was wondering from where does the value of min activation come (a_min = 0.01) ? Is there a sensitiv analysis for this term ?

In a forward-dynamic model a_min is needed to avoid some singularities. In an inverse kinematics does a_min still make sense ? And if yes why 0.01 and not 0.001 ?

And finally is it possible to change a_min directly on OpenSin 4.0, when I try directly in the GUI, I obtain this error :

Property 'minimum_activation' has an in invalid value. (details : Minimum activation cannot be less than 0.01).

[Thomas Uchida]

You can use a minimum activation of 0 with the Millard2012EquilibriumMuscle model provided there is some damping. An explanation can be found in this paper: Millard, M., Uchida, T., Seth, A., Delp, S.L. Flexing computational muscle: modeling and simulation of musculotendon dynamics. ASME Journal of Biomechanical Engineering 135(2):021005, 2013 (https://nmbl.stanford.edu/publications/ ... rd2013.pdf).