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CIP Axis Attributes
Chapter 4
Rockwell Automation Publication MOTION-RM003I-EN-P - February 2018
337
Strobe Command Position
Usage
Access
T
Data
Type
Default
Min
Max
Semantics of Values
Required - FPV
Get/
GSV
T
REAL
-
-
-
Position Units
Strobe Actual Position, Strobe Command Position and Strobe Master Offset
attributes are used to simultaneously store a snap-shot of the actual, command
position, and master offset position of an axis when the MGSP (Motion Group
Strobe Position) instruction is executed. The values are stored in the configured
Position Units of the axis.
Since the MGSP instruction simultaneously stores the actual and command
positions for all axes in the specified group of axes, the resultant Strobe Actual
Position, Strobe Command Position and Strobe Master Offset values for different
axes can be used to perform real-time calculations. For example, the Strobe Actual
Positions can be compared between two axes to provide a form of slip
compensation in web handling applications.
Start Command Position
Usage
Access
T
Data
Type
Default
Min
Max
Semantics of Values
Required - FPV
Get/
GSV
T
REAL
-
-
-
Position Units
Whenever a new motion planner instruction starts for an axis (for example, using
a MAM instruction), the value of the axis command position and actual position
is stored at the precise instant the motion begins. These values are stored as the
Start Command Position and Start Actual Position respectively in the configured
Position Units of the axis.
Start Positions are useful to correct for any motion occurring between the
detection of an event and the action initiated by the event. For instance, in coil
winding applications, Start Command Positions can be used in an expression to
compensate for overshooting the end of the bobbin before the gearing direction is
reversed.
If you know the position of the coil when the gearing direction was supposed to
change, and the position at which it actually changed (the Start Command
Position), you can calculate the amount of overshoot, and use it to correct the
position of the wire guide relative to the bobbin.