Rockwell Automation 1746-HSRV SLC Servo Control Module User Manual - Manual (Page 178)

Publication 1746-6.1.2 - July 2000
Input/Output Quick Reference A-5
Word 2 Parameters
1 s = Slot number for the SLC Servo Module.
2 A small number of Fits per CIT cause a fast servo loop closure time that yields better motion performance on the
transitions, but slower communication with the SLC processor. As the number of Fits per CIT increases, motion
performance on the transitions degrades, but communication with the SLC processor is slightly enhanced. For
blended moves, Fits per CIT must be greater than 4.
Multi-Word Parameters
Parameter Name
(Parameter Group) Destination M
FileLocation
1
Range Default Additional Information
Fits per CIT
(System) M0:s.2/0 through
M0:s.2/3 3 to 6 3 One coarse iteration represents the servo loop
closure time. The fine iteration time on the SLC
Servo Module is 1.6 msec. The default Fits per CIT
provides a 4.8 msec servo loop closure time.
2
Reserved M0:s.2/4 through
M0:s.2/15 0
Reserved M0:s.3 0
Parameter Name
(Parameter Group) Destination M
File Location
1
Range Default Additional Information
Reserved 0
Encoder Lines (Lines/
Rev)
(Feedback) M0:s.4,s.5 1.0 to 8000 1000.0
Counts per Position
Unit
(Feedback) M0:s.6,s.7 1.0 to 16909320.0 4000.0 This parameter specifies a conversion constant that
allows the module to convert position units into
internal resolution units and vice versa.
The module uses 4X encoder decoding (both edges
of channel A and B are counted). The count direction
is determined from both the direction of the edge
and the state of the opposite channel. Channel A
leads channel B for increasing count. This is the
most commonly used decode mode with incremental
encoders, since it provides the highest resolution.
Determine the parameters by using known
specifications of axis hardware components. For
example, if an axis has a 1000-line encoder directly
coupled to a 5 pitch lead screw (5 turns per inch) and
a position (unit of inches) for programming, the value
for the parameter is:
Counts per Position Unit = 1000 Lines/Rev
x 4 Counts/Line
x 5 Revs/Inch
= 20000 Counts/Inch.
For the position (unit of millimeters) for
programming, the value for the parameter is:
Counts per Position Unit = 20000/25.4 Counts/Millimeter