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Old 05-07-2018, 04:32 AM
baldoni9 baldoni9 is offline
Join Date: Aug 2016
Posts: 42
Default CoM location of trunk segments

I was wondering how the locations of the CoM of the trunk segments are defined, and I couldn't find the related info; are they based on literature data? If yes, could you please provide me with the literature reference?

Thank you,

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Old 05-08-2018, 11:36 AM
mkjung9980's Avatar
mkjung9980 mkjung9980 is offline
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Join Date: Aug 2009
Posts: 886

Dear Michele,

1) Following pieces of code will determine the CoM of the trunk segment:
  AnySeg ThoraxSeg = {

    AnyFolder &Data=..ModelParameters.ThoraxSeg;
    AnyFunTransform3D &Scale =..ScalingTrunk.ThoraxSeg.ScaleFunction;
    AnyVar MassS = ..Scaling.MassScaling.Trunk.MassScale;
    //Mass = 0.216*..BodyParRef.BodyMass; //Mass of Thorax concentrated in the CoM of the Thorax (Winter, 1990)
    AnyVar MassStandard = ..StandardParameters.Trunk.Mass;
    Mass = MassS*MassStandard;
    AnyVar UBHeight =  Data.UBHeight; //0.50; //Upperbody height
    AnyVar Radius = (Mass/(pi*UBHeight*1000))^0.5;
    AnyVar Ixx = 0.25*Mass*Radius^2 + 1/12*Mass*UBHeight^2;
    AnyVar Izz = Ixx;
    AnyVar Iyy = 0.5*Mass*Radius^2;
    AnyMat33 JMatRot = AnatomicalFrame.ARel*{{Ixx,0,0},{0,Iyy,0},{0,0,Izz}}*AnatomicalFrame.ARel';
    Jii = {JMatRot[0][0], JMatRot[1][1], JMatRot[2][2]};
    Jij = {JMatRot[1][0], JMatRot[2][1], JMatRot[2][0]};

    sCoM = Scale(Data.sCoM_pos);
    JaboutCoMOnOff = On;
2) Following pieces of the code contain the default parameter of the Trunk CoM:
('AMMR\Body\AAUHuman\Trunk\TrunkData1.1\ThoracicNo des.any')
AnyFolder ThoraxSeg = {

  AnyVec3 C1HatNode = {0.026,0.6,0};

  AnyVar UBHeight =  0.50; //Upperbody height
  AnyFloat sCoM_pos                                        = {0.060,0.303,0};
3) Following paper is the best reference for our trunk model:
De Zee, M., Hansen, L., Wong, C., Rasmussen, J., & Simonsen, E. B. (2007). A generic detailed rigid-body lumbar spine model. Journal of biomechanics, 40(6), 1219-1227.

4) If you have more questions which may not be well answered even after reading this reference, then could you please try to contact the first author (M. de Zee) by sending an email to his email address?
You can find his email address in the above reference.

I hope this may be helpful to you.

Best regards,

Moon Ki Jung, Ph.D, Application Engineer, AnyBody Technology A/S.

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