BodyKinematics Tool - acceleration

[Giulia Ghielmi]

Hello everyone!

I've a problem with the BodyKinematics Tool. I am trying to calculate the equilibrium of forces for each instant of time, the problem is related to the force of inertia and therefore the acceleration of each instant. To calculate the force of inertia i was thinking of using the acceleration values extracted from body kineamtics, but the values returned by opensim are not realistic (attached photo).
The type of movement I am analysing is walking.

Has anyone had the same problem and found a solution?

[Carmichael Ong]

Because of the way that OpenSim/Simbody works, accelerations calculated from BodyKinematics depends on applying all external forces to the model.

If you do not have these (e.g., ground reaction forces for walking), one work around is to use the velocity data from BodyKinematics and then do numerical differentiation in a post-processing step.