Rockwell Automation GMLC Reference Manual - Manual (Page 116)

Publication GMLC-5.2 - November 1999
Defining Homing 79
For example, if a return velocity of 0.1 inches per second (6 IPM) is
specified, the uncertainty of the home position is calculated as shown
below;
0.1 Inch/Second * 0.008 Seconds = 0.008 Inch
Homing to an Encoder Marker
This active homing sequence is useful for single turn rotary and linear
encoder applications since these have only one encoder marker for full
axis travel. When this sequence is performed, the axis moves in the
specified home direction at the specified homing velocity until the marker
is detected. The home position is assigned to the axis position
corresponding to the marker location, and the axis decelerates to a stop.
The axis then moves back to the home position at the specified return
velocity. The axis motions for this homing sequence are shown below.
Homing to a limit Switch and Marker
This is the most precise active homing sequence available. When this
sequence is performed, the axis moves in the specified homing velocity
until the home limit switch is detected. The axis then decelerates to a stop
and moves in the opposite direction at the specified return velocity until
the home limit switch is cleared. After clearing the home limit switch, the
axis continues in the same direction at the return velocity until the first
encoder marker is detected. The home position is assigned to the axis
position at the moment the marker is detected, and the axis then
decelerates to a stop. The axis then moves back to the home position at
the return velocity. Axis motions for this homing sequence are shown
below.
When Active Homing is chosen and either Limit Switch or Marker are
selected the following fields become active.
Direction
The Direction field sets whether Positive or Negative is used for the
default homing direction of the axis.