I'm trying to find the most simplified (though accurate) calculations for the dynamic model of a standard 6DOF serial robot (PUMA robot).
I found this great paper: https://www-cs.stanford.edu/group/manips/publications/pdfs/Armstrong_1986.pdf
The paper contains the full equations with 28 constants of the system, and it specifies the calculation for each constant.
However, I have a problem regarding the 6th link. It has the inertia symmetric values - Ixx6 Iyy6 Izz6, but Iyy6 never appears in any constant. The specific robot in the paper (and actually it should be for every robot) has a 6th link that Ixx6 = Iyy6, but the same is true for Ixx5 and Iyy5 and still they both appear in the constants.
Do you think this is a mistake? I need the exact equations has I want to expand them to the case of a payload - I want to replace m6 and I6 with updated values that include the payload mass and transferred inertia and then the equilibrium Ixx6 = Iyy6 will not necessarily exist.
Do you know of any other source of the full equations? Or maybe you have a solution to understand which of the Ixx6 relates to Ixx6 or Iyy6?