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In most cases, the gains Ki, Kp, and Aff scale proportionally with the change in total moving mass (or rotating inertia). For example, if the original moving mass increased from 10 kg to 12 kg, the gains Ki, Kp, and Aff should each be multiplied by 1.2 to maintain similar servo performance.

There are some points of caution. Note that the change is calculated from the total moving mass, which includes the stage mass as well as the payload. Also, it is the rotational inertia (in units of kg-m²) that matters for rotary systems. Rotary systems are usually more problematic because it is easy to have large changes in inertia for small physical changes in payload geometry.

In addition, changes to the payload may impact flexible vibration modes of the structure. Filters used for loop shaping may no longer be located properly. In extreme cases it is best to drop back on the gains, eliminate all filters, and work back from a clean system.

In all cases, it's best to finish with a Loop Transmission plot to fully quantify servo system performance.