Include contact forces in Reduced Residual Analysis

[Evan Dooley]

Hello,

I was wondering if it is possible to use a contact model as the external force input used during the reduced residual analysis?

Currently, if I run my model, which includes a foot contact model, through RRA attempting to follow results from inverse kinematics and with the vertical pelvis constraint set to zero, the model falls all the way through the floor. The foot contact model generates forces if I run inverse dynamics, so even if it wasn't perfect with the kinematics I would expect the body to fall through, but the feet to still be stuck above the floor plane.

Does anyone have any ideas on how to incorporate the contact model forces as part of an RRA analysis?

Thanks for your help,
Evan

[Aaron Fox]

Hi Evan,

It may not be exactly what you want, but OpenSim Moco includes a contract tracking feature which you can combine with kinematic tracking to get some consistency between your experimental kinematics/GRF and those tracked in a simulation (including the forces from contact elements). I've somewhat used this approach as a pseudo-RRA process recently to generate a dynamically consistent tracking simulation where the kinematics are slightly adjusted so that the contact force elements generate matched GRF signals.

Aaron