How is center of gravity and moments of inertia defined in tooldata?


I am trying to set up a new tool for IRB 6700 with IRC5. The tool is too large to use the loadidentify routine, so I am inputting values in manually from CAD. I am using Solid Edge to do this, which gives me the TCP, CG, orientation of principal axes, and principal moments of inertia. The principal moments of inertia that I have (i1,i2,i3), are about the principal axes, which are oriented differently than the tool0 coordinate system. In the tooldata for the new tool definition, it requires ix, iy, and iz for the moments of inertia. This seems to me like it would be the moments of inertia about the x, y, and z axes of the tool0 coordinate system. Is this correct, or is it about the pricipal axes? Can I just input the i1, i2, and i3 values for ix, iy, and iz?


  • Forge_Engineering
    edited June 2023
    Hi Mkehler,

    There is a section in the 'RAPID Instructions, Functions & Data Types' manual available under Help in RobotStudio, that describes each component of the tooldata data type. 

    It is the moment of inertia about the principal axes however you have to provide the rotation from the tool0 coordinate system to the principal axes. The coordinates for the centre of gravity are given relative to the wrist (tool 0) and the orientation of the principal axes relative to the wrist (tool0) are given in quarternion format. 

    To quote directly from the book:
    Robot held tool:

    The load of the tool, that is:

    The mass (weight) of the tool in kg.

    The center of gravity of the tool load (x, y and z) in mm, expressed in the wrist coordinate system

    The orientation of the principal inertial axes of moment of the tool expressed in the wrist coordinate system

    The moments of inertia around inertial axes of moment in kgm2. If all inertial components are defined as being 0 kgm2, the tool is handled as a point mass.

    Good Luck, 



  • mkehler
    Thanks, that's very helpful. I see it in the book now, not sure why I couldn't find it before.