Rockwell Automation GMLC Reference Manual User Manual
Page 522
Publication GMLC-5.2 - November 1999
485
Average Velocity
Average_Velocity is the current speed of a servo, master only or virtual
axis. It is measured in axis position units per second, and calculated by
averaging the actual velocity of the axis over the averaged velocity
timebase for that axis (entered in the motion controller’s application setup
menu). Average velocity is always a positive value regardless of which
direction the axis is moving.
In the Tag Explorer, select both Axis System Variables and the desired
axis, then select Average_Velocity in the Tag Window.
The resolution of the Average_Velocity variable is determined by the
current value of the Averaged Velocity Timebase parameter, and the
conversion constant K (feedback counts per position unit) for the axis.
The greater the averaged velocity timebase value, the better the speed
resolution, but the slower the response to changes in speed.
The average velocity resolution in position units per second may be
calculated using the equation below.
The minimum averaged velocity timebase value is one millisecond.
Values less than this default to 1 ms. See the Setup section of your motion
controller’s Installation and Setup manual for information on setting the
averaged velocity timebase and the conversion constant parameters.
For example, on an axis with position units of inches and a conversion
constant (K) of 20000, an averaged velocity timebase of 0.25 seconds
results in an average velocity resolution of
nit
Position U
Counts
Feedback
K
x
[Seconds]
Timebase
Velocity
Averaged
1
Minute
Inches
012
.
0
Second
Inches
0002
.
0
20000
x
25
.
0
1
=
=