Rockwell Automation GMLC Reference Manual - Manual (Page 168)

Publication GMLC-5.2 - November 1999
Imaginary Axis Applications 131
The Initialization module (below) enables feedback, reads the position
lock tolerance of the feed axis into the Lock_Tol_0 user variable (more on
this later) and gears the feed axis to the imaginary axis at a 1:1 ratio. Once
this gearing is established, you can move the feed axis either directly or
move the imaginary axis.
The main task feeds a given amount of material using an incremental
move of the imaginary axis and waits for completion. However, since
corrections are continuously being applied directly to the feed axis by the
correction task, the feed axis can still be moving (correcting) when the
imaginary axis is done. Therefore, use an On Expression block to
implement a custom “wait for axis lock” function in GML. This block
evaluates the following expression:
Absolute_value(Command_Position_Imaginary -
Actual_Position_Material) < Lock_Tol_0