Force plate measurement calculation

Hi, my name is Yi hwan.

In the “ForcePlateType2.any” there is COP and Tz calculation code.

that code is this

  AnyVar Vx= my/fzz;
  AnyVar Vy= -mx/fzz;
  AnyVar Vz= 0;
  AnyVar T_twist = mz-Vx*fy+Vy*fx;

but my question is that equation is different with amti force_plate manual

that manual explained that

Mx = FzY
My = - Fz
X
Mz = - FxY + FyX + Tz

therefore COP and Tz equations to be
X = -My/Fz
Y = Mx/Fz
Tz = Mz+FxY-FyX

both models are using same equation for Tz but different equation for COP

I want to know reason of two models are using different method.

Hi YiHwan

Let’s see some piece of ‘ForcePlateType2AutoDetection.any’ file in AMMR V1.3.

    AnyDrawVector vector =   {
      AnyVar time=..ForcePlateDriver.t;
      AnyVector Load=..load(time);
      AnyVar OnOff=iffun(gtfun(Load[2],-10.0),0.0,1.0);
      
      AnyVar fx= Load[0];
      AnyVar fy= Load[1];
      AnyVar fz= Load[2];
      
      //AnyVar lx=..ForcePlate.ydist;
      //AnyVar ly=..ForcePlate.xdist;
      //AnyVar lz=..ForcePlate.zdist;
      
      AnyVar mx= Load[3]*Folder.PointsScaleFactor;
      AnyVar my= Load[4]*Folder.PointsScaleFactor;
      AnyVar mz= Load[5]*Folder.PointsScaleFactor;
      
      AnyVar fzz =iffun(gtfun(  (fz^2)^0.5,0),fz,fz+1000000);
      
      AnyVar Vx= my/fzz;
      AnyVar Vy= -mx/fzz;
      AnyVar Vz= 0;
      
      
      [b]Vec = -..OnOff*{ Vx,Vy,Vz    };[/b]
      GlobalCoord=Off;
      PointAway = On;
      DrawCoord = Off;
      Line.Style=Line3DStyleFull;
      Line.RGB = {0,1,0};
      Line.Thickness = 0.000001;
      
      Line.End.Thickness = 2*0.015; 
      Line.End.Length = 4*0.015;  
      Line.End.Style=Line3DCapStyleEllipsoid;
      //
      Line.Start.Thickness = 0*0.015; 
      Line.Start.Length = 0*0.015;  
      Line.Start.Style=Line3DCapStyleEllipsoid;
      
      
      AnyRefFrame &ref = ..ForcePlate;
    };

So when this class template draws the center of pressure,
there is a minus sign.
So basically, we are using the same equation as you referenced.

Best regards,
Moonki