Rockwell Automation GMLC Reference Manual - Manual (Page 105)

Publication GMLC-5.2 - November 1999
68 Configuring Axis Use
Unwind Fraction
The Unwind Fraction lets you add a fractional count to the Unwind
Constant to more accurately define the Unwind value. The ability to
entire a fractional count for the unwind reduces the position error that can
accumulate per cycle.
The Unwind Fraction is entered in two parts: the numerator and the
denominator.
Numerator
The Unwind Fraction Numerator is the top value of the fraction being
added to the Unwind Constant. Valid Numerator values range from:
• 0 to 999,999,999
The maximum permissible value is the Unwind Fraction Denominator
value minus 1.
Denominator
The Unwind Fraction Denominator is the bottom portion of the Unwind
Fraction. Valid Denominator values range from:
• 1 to 1,000,000,000
Unwind Reference Point
If the axis is configured as a rotary axis in the General section of
Configure Axis Use, a value for the Unwind Reference point is requested.
This value is used when an unwind is performed on a rotary axis. The
Unwind Reference point is the position to which the axis rolls during an
unwind. The axis rotation position is equal to the Unwind Reference
Point plus the Unwind.
Rotation Point = Unwind Reference Point + Unwind
The total distance travelled before the axis unwinds remains constant and
is not affected by the Unwind Reference Point.