ScapulothoracicJoint Model IMU Placement Inconsistency

[Paul Klarich]

Hello OpenSim Team,

I have performing IK with IMU data on the ScapuloThoracic model through OpenSim4.1 via MatLab and have had some good results. I recently have been trying out the new IMU GUI features in the 4.2 beta release and have encountered an issue during IMU placement.

I have attached pictures of the resulting model after performing an IMU Placement on them. ST41 and ST41_2 reflect the model after performing IMU Placement via MatLab through OpenSim4.1. ST42 and ST42_2 reflect the model after performing IMU Placement via the GUI through OpenSim4.2, using the same .xml files used when working through MatLab and Open4.1.

I have also tried "powering through" the IMU placement issue to see if the IK produces the same result, but it does not. The links below are for videos of the motions produced through IK.

4.1
https://streamable.com/scga9t

4.2
https://streamable.com/hw52fm

I also noticed that the GUI converts Radians to Degrees for the Euler angles, so I tried using radians and the IMU placement did not produce similar results to what I got via MatLab and 4.1.