Rockwell Automation GMLC Reference Manual - Manual (Page 115)

Publication GMLC-5.2 - November 1999
78 Configuring Axis Use
• Absolute Serial: only for AEC-216 and AEC Transducer Types.
• Absolute MV (Motor Vernier): only for REC Transducer Type.
Important: The selection of a Transducer Type, in the Feedback page,
determines which homing procedures appear in this list.
Active Homing
Active homing is the most common homing procedure for physical servo
axes. When ACTIVE is selected, the desired homing sequence is selected
by specifying whether or not a home limit switch and/or encoder marker
is used for this axis. Active homing sequences always use trapezoidal
velocity profile. The available active homing sequences are described
below.
Homing Without a Limit Switch or Marker
This is the simplest active homing sequence. When this sequence is
performed the home position is immediately assigned to the current axis
position. This homing sequence produces no axis motion.
Homing to a Limit Switch
This active homing sequence is useful for multi-turn rotary and linear
applications where there are multiple encoder markers over full axis
travel or when an encoder marker is not available.
When this sequence is performed, the axis moves in the specified home
direction at the specified homing velocity until the home limit switch is
detected. The axis decelerates to a stop and then moves in the opposite
direction at the specified return velocity until the home limit switch is
cleared, and the axis decelerates to a stop. The axis then moves back to
the home position at the return velocity. The motions for this active
homing sequence are shown below.
Neglecting the mechanical uncertainty of the home limit switch, the
accuracy of this homing sequence depends on the time uncertainty in
detecting the home limit switch transitions. The position uncertainty of
the home limit switch (8 milliseconds) and the specified return velocity.