Joint moment contribution to acceleration of center of mass

[Hoon Kim]

Dear all,

I have several experiences to use IAA to calculate contributions of individual muscles to the acceleration of COM.
While I am using IAA, I was wondering if there is a way to calculate the contribution of each JOINT MOMENT to the acceleration of COM.
I would be so happy to hear any comments or tips about how to do that in OpenSim (e.g., how to create the IAA set file.xml or model actuator to calculate the contribution of each JOINT MOMENT to the acceleration of COM).
Thank you so much for any comments.

Sincerely,

Hoon

[Carmichael Ong]

I'm not sure if I've seen someone try this, but maybe here's something you could try. Since IAA calculates based on all actuators, if you could create another model with CoordinateActuator's or TorqueActuator's in place of muscles, and then apply the moments to these actuators (possibly through a PrescribedController(?)), this might be one way to go.

[Hoon Kim]

Thank you for the tips.

Could you help me apply the joint moment calculated by inverse dynamics to IAA?

I removed all muscle forces and added CoordinateActuator in the model. Then, I tried to add jointmoment.sto (ID results) to the control file in the IAA set file.
But, I think that doesn't work because the control file should be not moment but control (e.g., 0-1).

Could you give me a little bit of more detailed information about how I can apply the joint moment to the IAA?
Thank you so much for any helps.

Sincerely,

Hoon

[Carmichael Ong]

You could set the maximum limit of the coordinate actuator to the maximum joint torque, then divide all the values so that they are scaled 0-1. If you have both extension and flexion, you may have to make a couple coordinate actuators per degree of freedom, taking into account any negative signs.