Help - point kinematics to inverse dynamics

[Amy Stalker]

I am working on creating a dynamic leg press model, and am tyring to understand the effect of moving the point of force application from the heel to the toe, and eventually to other points on the foot. Right now the force on the heel files work just fine.

I have created two markers on the left and right toes and done a point kinematics analysis to track the x,y,z location of the marker. The data in the .sto files corresponds visually with the location of the toes with time. I put these x,y,z marker locations into the motion file, and then under the "external loads" tab, I chose the file containing the forces.

When I ran the simulation I received the error: "Tool execution failed or cancelled by user. Output files were not written."

The message in the bottom portion of the window said: "Exception: Array index out of bounds."

Does anyone know what this means in this context? I have the same number of rows, but different numbers of columns in motion file vs. the just forces file. This worked when the point was on the heels and I believe I did the exact same thing.

Thank you for your help,
Amy

[Ayman Habib]

Amy,

To use the file for external loads it has to contain both the point positions and the force being applied. Also the labels have some specific format/order. I suggest you take the file with the heel data (that works) and modify it to replace the "contents" of the columns labeled:
ground_force_px ground_force_py ground_force_pz
with the desired location.

If you want to change the force vector you'd do the same for the columns
ground_force_vx ground_force_vy ground_force_vz

The exception you see is thrown way down in a low level routine probably because of something wrong in the headers of the file but that wouldn't happen if you just change the contents and leave the header alone (except for the number of rows).

Good Luck,
-Ayman