Rockwell Automation GMLC Reference Manual - Manual (Page 162)

Publication GMLC-5.2 - November 1999
Using the Imaginary Axis in GML 125
Like other axes, you can configure the imaginary axis as either a rotary or
linear axis with its own position units, conversion constant and (if the axis
is rotary) unwind value. Select both the move and jog profiles, and set the
maximum speed, maximum acceleration, and maximum deceleration
values for the imaginary axis. Needless to say, hookup diagnostics and
self-tuning are not available for an imaginary axis. See the Setup section
of the Installation and Setup manual for your motion controller for
information on using the setup menus to configure the imaginary axis.
The conversion constant for the imaginary axis is essentially arbitrary, but
does affect the smoothness of gearing and position-lock cams that use the
imaginary axis as their master. For best results, set the position units and
conversion constant for the imaginary axis to the same values used for the
physical axis that is to be slaved to the imaginary axis.
Using the Imaginary Axis in GML
All motion blocks normally used for physical servo axes (Move Axis, Jog
Axis, Position-Lock Cam, etc.) can also be used with imaginary axes,
with the following exceptions:
• Home Axis
• Direct Drive Control
• Watch Control - Arm and Disarm Registration
• On Watch - Wait for Registration
Because feedback, drive, or registration inputs are not associated with an
imaginary axis, these blocks do not apply.
To home the imaginary axis, use the Redefine Position block to set the
command position of the imaginary axis to the desired value. For
example, the following selections home the imaginary axis to zero.