Compute velocity and acceleration of a segment

Hi,
I am trying to compute the acceleration of an individual segment (e.g. tibia) during a running trial. I have looked at the r, rDot, rDDot of individual segments. It doesn't calculate rDot or rDDot values during marker tracking. Is there any option in AnyBody to calculate the velocity and acceleration of an individual segment?

Thank you!
-Arif

Hi Arif,

That is true! The marker tracking study is a kinematic study which is set to solve only positions and not compute velocity and acceleration. This is mainly done for speed. The point is that the marker tracking is an over determinate analysis and to compute velocity and acceleration, the solver must do some perturbations instead of solving analytically as in the case of a determinate solver. This also means, the data can also be a little bit noisy...

If you want, you can enable velocity and acceleration analysis in Marker tracking. Please explore to Main.Studies.MarkerTracking.InitialConditions.PosAnalysisOnlyOnOff Main.Studies.MarkerTracking.Kinematics.PosAnalysisOnlyOnOff.

Right-click and locate these values in AnyScript and switch them to Off. You will find that these settings are defined in the AMMR folder and are not model specific settings. Please be aware if you change these settings in the AMMR folder, this will affect all the mocap models using your AMMR copy. (you can use the ??= operator to leave the default values and set the new values through your mocap model specfically).

I would suggest you let the marker tracking be as it is and obtain the velocity and acceleration values by running only the kinematics analysis of the inverse dynamics study.

Best regards,
Dave