Joint Reaction Analysis

[Nicholas Vandenberg]

Yeah, I think that's exactly what I'm seeing. And the final cost function value is on the same order of magnitude as my state tracking (albeit a lesser value), but I wonder if further reducing the weight on the goal will open up those weird muscle activations? That initial figure was from running the generic goal, not specifying to minimize Fy yet. My sim with isolating Fy specifically converged this morning, but it seems like it's still not quite doing what I want and I'm getting the higher JRFs from muscle activation during swing.

minFy_plot.png (55.94 KiB) Viewed 926 times

I'm also trying a sim where I'm isolating Fx, with the rationale being that it won't target the musculature with vertical lines of action like the glmed (which was still turned off) and maybe put more focus on constraining the hip flexors

[Nicholas Bianco]

What do the muscle activations look like from that solution? It would be helpful to see what you're talking about to get a sense of what's going on.

I'm also trying a sim where I'm isolating Fx, with the rationale being that it won't target the musculature with vertical lines of action like the glmed (which was still turned off) and maybe put more focus on constraining the hip flexors

Good idea, that would be an interesting comparison point.

[Nicholas Vandenberg]

Forgive the screenshot, I pulled some plots from the muscle activity across a few different JointReactionGoal condition sims. Here's some of the muscle forces from the 'main' amputated limb muscles crossing the hip joint when using the generic goal, minimizing Fy specifically, and minimizing Fx specifically.

HJRF_mus_Plots.png (227.76 KiB) Viewed 907 times

[Nicholas Bianco]

I'm suprised that the generic problem and "minimize Fx" problem produced the same solution. Do the gluts have relatively constant activation (as the fiber forces indicate)? If so, that's usually a sign that you need to tighten your convergence criteria.

[Nicholas Vandenberg]

Yeah, that was odd. Granted this is only a selection of the musculature, I imagine if I did a deeper dive there'd be some changes (hopefully). The glutes' activations are pretty constant so I'll look into that.

Thanks again, I appreciate all the time with troubleshooting this.
Nick