Translation between two segments

[ogrodnikj]

Hello,
I use AnyBody version 7.1.2.6044 and “Plug-in-gait_Simple” model.

I woudl like to calculate the translation between A) head of the femur and acetabulum, and between B) shank and femur.
Firstly I try do it for hip joint (A), and I changed the definition of “hip joint” use TransSphericalJoint function (instead SphericalJoint). However I coudn’t perform the Inverse dynamics.
Firstly I saw error:

ERROR(SCR.EXP0) : C:/U…s/J…a/D…p/N…)/A…o/Body/A…n/L…M/RightLegSelectedOutput.any(12) : ‘Hip_MediolateralForce’ : Error in expression. Please refer to the following error messages for details …
ERROR(SCR.EXP3) : C:/U…s/J…a/D…p/N…)/A…o/Body/A…n/L…M/RightLegSelectedOutput.any(12) : ‘Hip_MediolateralForce’ : Index [2] out of range for ‘AnyFloat[2]’

So, I bocked of code “Hip_MediolateralForce” (in SelectedOutput folder) into a comment. In this way two steps: LoadParameters and MarkerTracking in operation “RunAnalysis” were completed successfully. However “InverseDynamics” wasn’t completed and I saw comment:

Macro command : InverseDynamicView(1:1)> classoperation Main.ModelSetup.Views.InverseDynamicView"Set View"

Position analysis failed : 194 independent constraints and 196 unknowns
- attemps to continue (attempt no. 1)
Position analysis failed : 194 independent constraints and 196 unknowns
- attemps to continue (attempt no. 2)
Velocity and acceleration analysis failed : 166 independent constraints and 168 unknowns
Constraint violations for study ‘Main.Studies.InverseDynamicStudy’ :
ERROR(OBJ.MCH.KIN1) : C:/U…s/J…a/D…p/N…)/A…o/T…s/A…p/AnyMoCapModel.any(59) : InverseDynamicStudy.InitialConditions : Model is kinematically indeterminate :

1. Could you help me, where is the problem in my model?
2. How should I change the definition of (A) hip joint and (B)knee joint to calculate the translation between head of the femur and acetabulum and between femur and shank, respectively (in x, y, z direction).

Thank you very much for your help.
Best regards,
Justyna

[mkjung9980]

Dear Justyna,

There may be two different ways to achieve what you want to implement.

1. Changing the types of the hip and the knee joints:
   If you changed the joint type as you want, then also you need to adjust the following two files in your AnyMoCap model base folder:
   ‘JointAngleOutputs.any’
   ‘JointAndDriversOptimized.any’
   Because you should also write the translations of those joints in the output files. Then you can read those values for inverse dynamics.

2. Using FDK feature.
   This will be more challenging. Sometimes you need to model some relevant ligaments around the knee joint as well as some proper contacts.

For hip, I would recommend you to see the ‘THA-KneeBendDemo’ model in the Examples folder of the AMMR.
For knee, I would recommend you to have a look at this paper: http://dx.doi.org/10.1115/1.4029258

Best regards,
Moonki