See the Documentation (Adams Basic Package > Adams View > Adams View > Editing Modeling Objects > Modifying Geometry and Part Properties > Modifying Part Properties : About Entering Mass Moments of Inertia):
where "x, y, and z are the components of the displacement of an infinitesimal mass particle of mass dm, measured from the origin of the inertia marker in the coordinate system of the inertia marker."
Note that the sign convention for these terms can cause some confusion; please see the following articles which discuss this:
I am investigating the moments of inertia IXX, IYY, IZZ, IXY, IZX and IYZ of the vehicle about the vehicle COG.
To calculate the moments of inertia to the vehicle COG I evaluate the moments of inertia for each part (Ixx, Iyy, Izz, Ixy, Izx, Iyz) and add mass (m) multiplied with distance of the part COG to vehicle COG (dx, dy,dz) according to the Steiner law for each part :
IXX = Ixx + m*(dy**2+dz**2)
IYY = Iyy + m*(dx**2+dz**2)
IZZ= Izz + m*(dx**2+dy**2)
IXY = Ixy + m*(dz**2)
IZX = Izx + m*(dy**2)
IYZ= Iyz + m*(dx**2)
The results are the moments of inertia for each part in vehicle assembly to vehicle COG (IXX,IYY,IZZ, IXY,IZX,IYZ).
The Vehicle Inertia is sum of part moment of inertia for all parts in vehicle.
Vehicle IXX = ∑ IXX
Vehicle IYY = ∑ IYY
Vehicle IZZ = ∑ IZZ
Vehicle IXY = ∑ IXY
Vehicle IZX = ∑ IZX
Vehicle IYZ = ∑ IYZ
When I compare the results of the aggregate mass and calculation:
there is a good correlation in the vehicle IXX, IYY and IZZ but there is a significant difference in the vehicle IXY, IZX and IYZ.
Where I done the mistake during the calculation of the vehicle IXY, IZX and IYZ?
The other workaround would be to always request values with respect to ground.origo
If I'd doubt the whole calculation I'd apply the aggregate mass stuff to a simple model with a single part/geometry with known values (analytically derived).
