Apply moment to center of mass

Hello everyone

My name is Ramona and I am currently working with AnyBody for my master thesis at ETH Zurich. The goal is to simulate stand-sit-stand tasks. As the model I am using does not include arms, I try to model their contribution to keep balance while performing the task by a moment (AnyMoment3D). Preferably I would like this moment to be applied at the center of mass, but I am not sure, if this works, as I could not achieve it so far.

Therefore my question: Is it possible to apply a moment to the center of mass of a model and if yes, how would I best do this?

Ramona

Dear Ramona,

AnyBody has its AnyKinCoM measure in order to measure the COM of some selected segments.

If you apply a kind of ‘force’ on this measure then that force effect will be distributed on the selected segments.

But you can’t apply a kind of ‘moment’ on this AnyKinCoM measure.

Best regards,
Moonki

Dear Moonki,

I was trying out a little bit myself as well and I think I found a way to achieve, what I want…

I have a segment for visualizing the center of mass during analysis. This segment and its drivers are defined as described in the thread “Draw the Center of Mass position during Analysis” (http://forum.anyscript.org/showthread.php?t=2223&highlight=visualize+center+mass).

I just applied the moment to this segment, which does not have a mass itself and it seems to do the job.

Best regards,
Ramona

Dear Ramona,

Of course this is a convenient way in order to display the center of mass using a massless segment.

Also you need to control the orientation of that dummy(massless) segment.

But also you should define a reaction which is related to that orientation.

So there should be a reaction which covers that orientation between human and the dummy segment.

Then you should select a segment on human for that reaction.
Then your applied torque will be transferred to that segment on human.

But it is ambiguous to choose only one segment for that purpose.
You can simply try to choose the pelvis segment for that.
But your applied torque will not be distributed over all segments.

Best regards,
Moonki