We are in the process of uploading a OpenSim v4.x version (read, as in today) that will have a viewable ribcage (among other subtle, but soundly based mods).
Thanks for using our model, and please let us know if you have any questions.
Jake Banks

Good deal. Glad to that I could help. FYI: If your using Thelen muscles, consider switching to Millards. In OpenSim >4 the Thelen muscle's lowest activation is .01, while Millard's can go to 0. You'll want to recalculate/find your PEC forces, as the curves are slightly different. You can switch musc...

I assume you mean 'weld' or 'locked' the shoulder coordinate instead of 'blocked'? If so, a other things to consider then (perhaps in this order): - Inverse Dynamics is just a frame-by-frame (i.e. incremental times) calculation of the joint demands. Even in a very simple single pendulum model (like ...

Perhaps your signs are flipped... have you tried adding the passive torques instead of subtracting them?
Otherwise, are you also applying a similar method to account for shoulder joint flexion (assuming you have that DoF)? If not, biarticular muscles may be impacting moment arms and passive lengths.

I'm having a very similar issue ( assigning an actuator force and SOpt not considering it ). I've been testing variations of an approach posted a few years ago: https://simtk.org/plugins/phpBB/viewtopicPhpbb.php?f=91&t=6499&p=29752&start=0&view= I don't get any error's, but SOpt simply does not cons...

If lowering the actuator's contribution doesn't do the trick, you can always develop an API which considers EMG. For a shameless plug, please see the attached abstract introducing our implementation of Cholewicki's EMG optimization method with opensim + Matlab (we are in the process of submitting a ...

Thank you very much for the timely response. It helps explain what SOpt is doing, but it still does not explain (to me anyways) the results I am getting. How could my GRFs not be contributing to my SOpt solution? I am getting the same results regardless of applying a GRF or not. I can even make the ...

I am looking for some clarity on how SOpt determines the moments it balances. I have read in the documentation and in a previous posts about some of the subtle differences between how the SOpt and Inverse Dynamics moments are calculated, but they do not explain the issue I am having. I am using a mo...