Center of Mass for Mobile Multibody

[Umer Huzaifa]

Hi there,

I am learning Opensim to develop wearable devices for assistance in walking and want to monitor the effect on the center of mass as the walking algorithm runs on the device. I am looking into DynamicWalker challenge tutorial to get started. However, as I try osimmodel.calcMassCenterPosition with the necessary arguments, the answer comes out to be [Nan, Nan, Nan] because platform_rz is locked in the inclined position (as also mentioned in the warning that pops up in the MATLAB command window).

Is there a way, I could just extract the center of mass of the walker itself and not the platform included in it? If there is no built-in command, I am ready to write my own expression for center of mass using the positions and masses of individual links but want to make sure first that there is no other way.

Thanks!