simtk.org

How can I choose the optimal forces during RRA?
for: FX, FY, FZ, MX, MY, MZ and all coordinates (like in the file gait2354_RRA_Actuators.xml).

I'm doing a gait simulation...
Thanks to all for the answers

Hi Bruno,

I'd suggest running InverseDynamics analysis to find out what Forces/Torques are needed and use the maximum as optimal force to account for unactuated/under-actuated degrees of freedom.

Hope this helps,
-Ayman

ok, from InverseDynamic I have these results:
(max absolute values)
pelvis_tilt_moment= 22.96
pelvis_list_moment= 28.5
pelvis_rotation_moment= 6.73
pelvis_tx_force= 33.29
pelvis_ty_force= 96.15
pelvis_tz_force= 49.29
hip_flexion_r_moment= 47.43
hip_adduction_r_moment= 12.53
hip_rotation_r_moment= 3.4
knee_angle_r_moment= 30.88
ankle_angle_r_moment= 2.87
subtalar_angle_r_moment= 0.64
hip_flexion_l_moment= 51
hip_adduction_l_moment= 51.58
hip_rotation_l_moment= 10.72
knee_angle_l_moment= 43.35
ankle_angle_l_moment= 100.92
subtalar_angle_l_moment= 6.91
lumbar_extension_moment= 10.77
lumbar_bending_moment= 16.15
lumbar_rotation_moment= 5.82
Now for you, what are the values of residuals (FX, FY, FZ, MX, MY, MZ) to choose?

Hi Bruno,

As Ayman suggested, you will use these results to choose the optimal forces for the residuals actuators in RRA (i.e., FX, FY, FZ, MX, MY, MZ). But what is not clear is that these are named differently in the Inverse Dynamics solution. For example, pelvis_tx_force corresponds to FX.

pelvis_tx_force ==> FX
pelvis_ty_force ==> FY
pelvis_tz_force ==> FZ
pelvis_tilt_moment ==> MZ
pelvis_list_moment ==> MX
pelvis_rotation_moment ==> MY

So try setting the optimal force for the residual actuators in the actuators file equal or greater than the corresponding max from inverse dynamics.

Hope this helps.

Best,
Sam