User manual

178 Rockwell Automation Publication MOTION-UM003F-EN-P - March 2015
Chapter 8 Home an Axis
Active home to marker in forward bidirectional The marker homing sequence is useful for single-turn rotary and linear encoder applications because these applications
have one encoder marker only for full axis travel.
These steps occur during the sequence.
1. The axis moves in the Home Direction at the Home Speed to the marker and stops.
2. The axis moves back to the marker or it moves to the Offset position. The axis moves at the Home Return Speed. If the
axis is a Rotary Axis, the move back to the Home Position takes the shortest path (that is, no more than a half
revolution).
The accuracy of this homing sequence depends on the homing speed and the delay to detect the marker transition.
Uncertainty = Home Speed x delay to detect the marker.
Example: Suppose your Home Speed is 1 in/s and it takes 1 μs to detect the marker.
Uncertainty = 1 In./s x 0.000001 s = 0.000001 in.
Table 22 - Active Homing Examples (Continued)
Sequence Description
Homing Vel
Return Vel
Axis Position
Axis Velocity
1
2
1: Encoder Marker Detected
2: Home Position
Active Bidirectional Home with Marker