Sum of forces not equal to zero

Main Forum
1

Hi all

So I am working with the shoulder model and trying to reduce the 20 muscle forces to one resultant force.

However, when I export all the forces (muscle and joint/ligament reaction forces) and add the components together, it is not zero; which actually should be, assuming quasi static conditions for the inverse dynamics, right? :confused:

Can someone tell me why it is? I am pretty sure my calculations are right.

Thank you!
Best, Seline

2

Hi Seline,

No, it should sum up to the inertial forces. It should be a perfect 0 for a static posture - please try.

Kind regards,
Pavel