Components of ground reaction force as the input of inverse dynamics

[Zhenwei Liu]

Hi,
I looked up the ground reaction force file called "subject01_walk1_grf.mot" given by "Gait2354_Simbody" model. In that file, it has twelve different components of the ground reaction force: ground_force_vx, ground_force_vy, ground_force_vz; ground_force_px, ground_force_py, ground_force_pz; ground_torque_x, ground_torque_y, ground_torque_z. Could anyone explain to me what those forces stand for? Thanks a lot!

[Vishal R]

There is a tutorial on performing ID using the external loads. Please have a look at it

https://simtk-confluence.stanford.edu/d ... +in+Stance

An excerpt from the tutorial explains what each columns represent :

Force Columns: select "ground_force_vx" from the first drop-down box; "ground_force_vy" and "ground_force_vz" will be selected automatically.
Point Columns: select "ground_force_px" from the first drop-down box; the corresponding "y" and "z" entries will again be populated automatically.
The GRF free moment is a torque, so check "Applies Torque".
Torque Columns: select "ground_torque_x", "ground_torque_y", and "ground_torque_z".

Cheers

[Zhenwei Liu]

Thank you so much! So does ground_force_p mean the position of the point to which we apply external load?