Rockwell Automation 1771-QC , D17716.5.25 SER/B SERVO POS - Manual (Page 36)

Positioning with Allen-Bradley PC
Chapter 4
4Ć12
axis stops on the marker. The servo positioning assembly then sets it
position register to the home position value you specify in the parameter
block. This initializes the axis position scale. Figure 4.10 shows how the
home position value you specify in the parameter block can affect the axis
position scale. This figure compares the scales for an axis after search
home operations with different home position values form the parameter
block representing the same physical position.
Figure 4.10
Axis Position Scales for 2 Home Position Values
Ć2 0
Home
3.00 +9 Parameter Block Home
Position Value=3.00
Parameter Block Home
Position ValueĆ5.00
Ć10 Ć5.00 0 +1
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Preset
Through a command block, you can command the servo positioning
assembly to preset a specified value into its position register. When the
servo positioning assembly executes a preset command, it sets its position
register to the specified value without causing axis motion. This action
effectively shifts the axis position scale. Figure 4.11 shows an axis
position scale before and after a preset operation.
Figure 4.11
Axis Position Scale before and after Preset
After Preset (1.5)
Before Preset
Ć5 0 +5
Ć5 0 1.5 +5
11009