Rockwell Automation 20D PowerFlex 700S with Phase I Control Reference Manual - Manual (Page 67)

Rockwell Automation Publication PFLEX-RM002D-EN-E - August 2013 67
Detail Drive Configuration and Operation Chapter 1
Inertia Adaptation Inertia adaptation is used to compensate for lost motion, which occurs when a
gear box and/or “springy” coupling is present. Inertia adaptation can allow the
user to increase the speed regulator bandwidth by up to four times.
For example, a motor connected to a gearbox is shown:
This gearbox can be represented by a spring (k) and gear back lash (BL):
When the speed of the motor increases, there is a period of time (represented by
Dx) before the teeth of the gearbox engage. After that time, there will be some
twisting (like a spring) in the shaft after the teeth of the gearbox engage. This lost
motion causes mechanical instability and limits how high the speed regulator
bandwidth can be set without causing instability. Inertia adaptation detects the
lost motion and a higher speed regulator bandwidth can be achieved without
instability.