Verifying IAA induced constraints

[Pia Stefanek]

Hi,

I try to do a verification of induced constraints (rolling-without-slipping) versus experimental GRF, during Walking. I have a Problem with the verification of the Moments/Torques. I read the post of Adam Yoder (viewtopicPhpbb.php?f=1398&t=8339&p=0&st ... 0920dde618) who had the same Problem.

I am not sure if I understood correctly how he solved the Problem. I set the external Forces from Point force to Body force and applied them to Calcaneus. Then I performed IAA. The constraint reaction Ground Forces (total_ground_force_ground_Fx,total_ground_force_ground_Fy,total_ground_force_ground_Fz) are similar to the Ground reaction forces of the external load file (ground_force_vx,ground_force_vy,ground_force_vz) but the constraint reaction Moments are all Zero (total_ground_force_calcn_r_Mx,total_ground_force_calcn_r_My,total_ground_force_calcn_r_Mz). The Ground reaction Moments of the external loads file are similar to Zero but not exactly (ground_torque_x,ground_torque_y,ground_torque_z).

Does anybody know the reason for this?

Thanks in advance.

Regards
Pia

[jimmy d]

It is not clear what your issue is. There will be a difference between the experimental Ground Reaction Forces and the constraint forces. This paper describes the rolling constraint and has figures showing differences.

This paper also describes some validation tips;

Contact forces and moments are within 2 SD of experimental data (e.g., ground contact forces and moments) for similar motion.