Rockwell Automation GMLC Reference Manual - Manual (Page 862)

Publication GMLC-5.2 - November 1999
Chapter
39
Merging Different Motion Types
Merge From Jog, CAM, or Gear
When merging a slave axis from actual-position gearing, or camming to a
move or jog by selecting Merge from Jog, CAM or Gear and At Current
Speed, in a Move Axis or Jog Axis block in GML Commander, as shown
below, the speed of the move or jog is not always exactly the same as the
previous gearing speed.
In fact, if the master speed is low enough, occasionally the move or jog
doesn’t work at all—the axis just sits there and doesn’t move. The reason
is that it has to do with how axis velocity is calculated inside the motion
controller.
The actual velocity of an axis (used when merging at current speed) is the
change rate of axis position every servo update. Since position can only
change by whole counts, the resolution of the actual velocity value is ±1
count per servo update. For example, with a servo update rate of 1 kHz
and 4,000 counts per revolution, actual velocity resolution is shown in the
following equation:
RPM 15
Minute
Seconds
60 x
Second 001 . 0
Update 1
x
Counts 4000
volution Re 1
x
Update
Count
1
± = ±