Rockwell Automation 1784-PM16SE SoftLogix Motion Card Setup and Configuration Manual - Manual (Page 297)

Publication 1784-UM003A-EN-P – June 2003
Motion Object Attributes 289
Rotary Axis When the Rotary Axis attribute is set true (1), it enables the rotary unwind
capability of the axis. This feature provides infinite position range by
unwinding the axis position whenever the axis moves through a complete
physical revolution. The number of encoder counts per physical revolution of
the axis is specified by the Position Unwind attribute. If the Rotary Axis
attribute is false (0), indicating linear operation, the maximum total linear
excursion is limited to 1 Billion feedback counts before rolling over to zero.
Position Unwind If the axis is configured as a rotary axis by setting the corresponding Rotary
Axis bit Servo Configuration Bit word, a value for the Position Unwind
attribute is required. This is the value used to perform automatic electronic
unwind of the rotary axis. Electronic unwind allows infinite position range for
rotary axes by subtracting the unwind value from both the actual and
command position every time the axis makes a complete revolution. To avoid
accumulated error due to round-off with irrational conversion constants, the
unwind value is requested in units feedback counts per axis revolution and
must be an integer.
For example, suppose that a given axis is configured as a Rotary Axis with
Position Units of “Degrees” and 10 feedback counts per degree. It is desired
to unwind the axis position after every revolution. In this case, the Position
Unwind attribute should be set to 3600 since there are 3600 feedback counts
(10 * 360) per revolution of the axis.
Motion Homing
Configuration
Home Mode There are currently three Homing Modes supported by the Motion Axis
Object, active, passive, and absolute. Active homing is the most common
homing procedure for physical servo axes.
GSV/SSV Access Attribute Name Data Type Values
SSV/GSV Rotary Axis SINT 0 = Linear
1 = Rotary
GSV/SSV Access Attribute Name Data Type Values
SSV/GSV Position Unwind DINT Counts per Revolution
GSV/SSV Access Attribute Name Data Type Values
SSV/GSV Home Mode SINT Enumeration:
0 = passive
1 = active (default)
2 = absolute