Inertia units: Payload Checker vs Robot (kg*m*s^2 vs kg*cm*s^2)

  • Hey, all, stupid question: The Fanuc payload checker spreadsheet takes inertias in kg*m*s^2, but the robot payload setup screen takes kg*cm*s^2.


    What's the conversion factor between these two units? I mean, if I'm handed a printout of the spreadsheet from the mechanical design department, how do I transcribe that into the robot? Do I just multiply by 100, since there's 100cm to every meter? Or is there another factor I need to be wary of here?

  • Hey, all, stupid question: The Fanuc payload checker spreadsheet takes inertias in kg*m*s^2, but the robot payload setup screen takes kg*cm*s^2.


    What's the conversion factor between these two units? I mean, if I'm handed a printout of the spreadsheet from the mechanical design department, how do I transcribe that into the robot? Do I just multiply by 100, since there's 100cm to every meter? Or is there another factor I need to be wary of here?

    You were right on with the multiply by 100. I looked at the current payload checker and found this conversion listed there:

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  • I got you. I posted this elsewhere as a duplicate.


    You want to put in the primary values Ixx, Iyy, and Izz from the CAD export. I assumed the values are from the flange and not about the center of mass. Corrected: Values are about center of mass.

    Select kg and m for the units for CAD.

    Use this: 1 kg*m2 = 10.197 kgf*cm*s2




    If you need convincing, the conversion is as follows:

    First, know that 1kgf = m*g = kg * (9.81)m/s^2=9.81N

    Start with what CAD gives you in regular units: kg*m^2

    -Then, multiply by (s^2/s^2)

    kg*m^2*(s^2/s^2) = (kg*m/s^2)(m)(s^2)

    Note: 1 kg*m/s^2 = 1N

    Substituting, you have

    (kg*m/s^2)(m)(s^2) = (N)*m*s^2

    Next, you sub 1kgf = 9.81N

    (N)*m*s^2 *(1kgf/9.81N) = kgf*m*s^2/9.81

    Finally, convert m -> cm: 1m/100cm

    (kgf*m*s^2/9.81)(100cm/1m) = (100/9.81) kgf*cm*s^2


    =10.194 kgf*cm*s^2

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