questions for modify the "GaitLowerExtremity" model

Hello everyone, I want to use AMMRV1.3 “ GaitLowerExtremity” to do some work but I don’t have the upper body marker trajectories, such as “RFHD”, “CLAV”, “C7”, “RBAK” et al, I just got the trajectories of pelvis and lower markers, I think I need to modify something in order to make my model move but I have no idea what should I start? Thank you for your suggestions[FONT=Wingdings]J[/FONT]


you have to modify the ModelSetup.any file:

MarkerLabels = {"RASI","LASI", ...etc  

This line has to fit your c3d data. You can look into your file with MlsViewer or a c3d editor.

Then create new markers: add something like this:

CreateMarker RTTU (
  Model1=MotionAndParameterOptimizationModel,Model2= InverseDynamicModel
  ) = {
    sRelOpt = {0.307,-0.56, 0.21};  };

The name (here RTTU has to fit one of your new marker names like in “MarkerLabels”)
MarkerPlacement defines which segment the marker will drive.
sRelOpt are the coordinates where the marker will be created, related to the coordinate system of the associated segment.

You have to adjust every marker to the segments as they were placed on the body. Good luck!

Best regards

Thank you. But I came across that when I just delete the markers that above the pelvis, the AnyBody modeling system will give a hint that there is something wrong with the initial position, like the following:

Position analysis failed : 282 independent constraints and 286 unknowns
- attempts to continue (attempt no. 1)
WARNING! NAN reached!
Unexpected error in computational kernel
ERROR(OBJ.MCH.KIN3) : E:/Temp/A…3/A…n/E…s/G…y/GaitLowerExtremity.main.any : KinematicStudyForParameterIdentification.InitialConditions : Kinematic analysis failed in time step 0

so I think I need to fix the pelvis’s movement with the spine but I have no idea about that…how it works in this model repository


Please see the other related posting on this issue,

You need to drive the pelvisthoraxrotation and the neck joint.

Please have a look in the JointsAndDriver.any file of the FreePostureModel for an example on the syntax for such drivers.

Best regards