258 Rockwell Automation Publication MOTION-UM003K-EN-P - January 2019
Chapter 12 Homing
Examples
This section contains examples of active and passive homing.
Active Homing
The examples in Ta ble 56 show different ways to use active homing.
Table 56 - Active Homing Examples
Sequence Description
Active immediate home This sequence sets the axis position to the Home Position without moving the axis. If feedback isn’t enabled, this sequence
enables feedback.
Active home to switch in forward bidirectional The switch homing sequence is useful for multi-turn rotary and linear applications.
These steps occur during the sequence.
1. The axis moves in the Home Direction at the Home Speed to the home limit switch and stops.
2. The axis reverses direction and moves at the Home Return Speed until it clears the home limit switch and then stops.
3. The axis moves back to the home limit switch 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).
If the axis is past the home limit switch at the start of the homing sequence, the axis reverses direction and starts the return
leg of the homing sequence.
Use a Home Return Speed that is slower than the Home Speed to increase the homing accuracy. The accuracy of this
sequence depends on the return speed and the delay to detect the transition of the home limit switch.
Uncertainty = Home Return Speed x delay to detect the home limit switch.
Example: Suppose that your Home Return Speed is 0.1 in./s and it takes 10 ms to detect the home limit switch.
Uncertainty = 0.1 in./s x 0.01 s = 0.001 in.
The mechanical uncertainty of the home limit switch also affects the homing accuracy.
Homing Vel
Return Vel
Axis Position
Axis Velocity
1
3
2
1: Home Limit Switch Detected
2: Home Limit Switch Cleared
3: Home Position
Active Bidirectional Home with Switch then Marker
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