Rockwell Automation 21G PowerFlex 750-Series AC Drives Reference Manual - Manual (Page 56)

56 Rockwell Automation Publication 750-RM001F-EN-P - February 2012
Chapter 5 General Device and Feedback Monitoring Configuration
Dual Feedback Position Discrepancy Tolerance
The Dual Feedback Position Discrepancy Tolerance, P41[Fbk Pos Tol]
parameter defines the cumulative position discrepancy that will be tolerated
between encoder 1 and encoder 2. The position discrepancy is defined as
position change relative to encoder 1.
This discrepancy checking is performed only while the [Fbk Mode] parameter is
equal to one of these values.
This table defines the legal values for each Feedback mode value.
If an illegal value is detected, an Invalid Configuration fault occurs and the safety
option remains in the Safe State.
IMPORTANT The relative position discrepancy difference is reset to zero at each Safe Stop
Reset.
Feedback Mode, P27 [Fbk Mode] Parameter Settings
1 Dual encoder with speed and position discrepancy checking
3 Dual encoder with position discrepancy checking
Feedback Mode, P27 [Fbk Mode] Values Dual Feedback Position Discrepancy Tolerance, P41
[Fbk Pos Tol] Legal Values
0 One encoder 0
1 Dual encoder with speed and position
discrepancy 1…65,535 in degrees (rotary encoders) or mm (linear
encoders) relative to the resolution of encoder 1
2 Dual encoder with speed discrepancy checking 0
3 Dual encoder with position discrepancy
checking 1…65,535 in degrees (rotary encoders) or mm (linear
encoders) relative to the resolution of encoder 1
IMPORTANT When setting discrepancy tolerances, consider that configuring a high gear
ratio between encoder 1 and encoder 2 could lead to unexpected dual
feedback position faults. This is because a very large encoder 1 movement
would translate into a very small encoder 2 movement.