Allen-Bradley ControlLogix Reference Manual

Chapter 4
CIP Axis Attributes
332 Rockwell Automation Publication MOTION-RM003I-EN-P - February 2018
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 and Strobe Command Position 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 Actual Position
Usage Access T Data
Type
Default Min Max Semantics of Values
Required - All 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.
Average Velocity
Usage Access T Data
Type
Default Min Max Semantics of Values
Required - All Get/GSV T REAL - - - Position Units / Sec
The Average Velocity attribute is the current speed and direction of an axis in the
configured Position Units per second of the axis.
Unlike the Actual Velocity attribute value, it is calculated by averaging the actual
velocity of the axis over the configured Average Velocity Timebase for that axis.
Average velocity is a signed value with the sign indicating the direction the axis is
currently moving.
The resolution of the Average Velocity variable is determined by the current value
of the Averaged Velocity Timebase parameter, and the configured Conversion
Constant (feedback counts per Position Unit) for the axis. The Average Velocity

Allen-Bradley ControlLogix Specifications

General

Brand	Allen-Bradley
Model	ControlLogix
Category	Industrial Electrical
Language	English