Rockwell Automation 9329 Drive Application Software - Manual (Page 8)

FM – Inertia Compensation
Drive Application Software – page 8 of 30
3.0 Overview
Diameter calculation is the process by which a dynamically changing roll diameter is
mathematically calculated during machine operation. In center driven winding and unwinding
applications, the actual diameter of the driven section changes as product is wound about the axis
or unwound from the axis. As the diameter of the driven section changes it is necessary to
change the axial speed and torque in order to maintain constant surface speed and tension on the
product. Diameter calculation can also be used to calculate the change in total reflected inertia.
This is typically used to profile the speed loop gain and in inertia compensation.
3.1 Diameter effects on surface speed
If the rotational speed of the driven section is kept constant, the surface speed will increase
as the diameter of the section increases. To maintain constant surface speed, the rotational
speed must decrease proportional to the increase in roll diameter. If the roll diameter
doubles, the rotational speed must be reduced by half to maintain constant surface speed.
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Roll Diameter (in)
Speed
Motor Speed (Rpm)
Surface Spd (Fpm)
*GearRatio
er(ft)*p RollDiamet
Fpm) LineSpeed(
(Rpm) MotorSpeed
12
er(in) RollDiamet
er(ft) RollDiamet
=
=