Rockwell Automation 4100 REC Resolver to Encoder Converter Installation and Setup Manual - Manual (Page 39)

Publication 999-126 - February 1996
32 Setup
If the travel range was defined to be 0 =< travel <256 and the axis
homed, after moving it slightly negative of the (zero) position, the
controller would think that the axis was near 256 instead of near zero.
The internal travel range allows the axis to dither about zero by -5
turns thus eliminating unwanted roll over at the alignment position. If
you homed the axis after moving it slightly negative of -5 the axis
position would roll over to just less than 251.
When you use a single resolver, the absolute travel range is 0 <=
travel < 1 turns (for geared resolver packages with a 1:1 gear ratio).
There is no built-in procedure implemented in the control to handle
dither about the alignment (zero) position. If you desire a dither
feature, you can use the algorithm shown below to program a dither
value. This value is typically a small percentage of the travel range.
Inside a Home block select:
•Normal
•Wait for Completion
Inside an If block build the expression:
•Actual Position >= (1 + dither value)
Inside the Redefine Position block:
•Select Relative
•Select Actual
•Enter -1
Defining a Non-Zero Home Position When you align the transducer to the physical axis using the Align
Absolute Transducer routine, the routine adjusts the home position to
offset the transducer position to zero.
Important: We recommend that you do not change the home
position established by the Align Absolute Transducer
routine.
You can establish a non-zero reference point using the GML Redefine
Position command after a Home command.
Defining the Redefine Position Command
After you have executed the home command, you need to define the
Redefine Position Command. To define the Redefine Position
Command:
1. Create a Redefine Position block and place it next to the Home
Axis block.
2. Double-click on the Redefine Position block.