Unreasonable result with forward dynamics

[mehri makki]

Dear everyone,

I have a question about joint reaction analysis example (double pendulum at wiki).
I’m trying to validate the time response that is calculated by OpenSim (Forward Dynamics Analysis) with that I capture from theory by developing equations of motion in MATLAB.
Once I solve the system dynamics in OpenSim and animate the motion, I see after a certain time for example t the system doesn’t move anymore and stops; while it is a periodic motion and there is no reason that system stops suddenly.
Do you have any idea why this happens and how I can solve it.

[Ayman Habib]

Hi Mehri,

When you run ForwardTool you need to specify start and end time, if the motion is periodic you should be able to do one cycle. In the case where you need to provide controls/actuation these has to go over the whole specified time range.

Hope this helps,
-Ayman