Chapter 4
What You Need to Know about Moves
4-6
ni.com
You can calculate this minimum velocity increment in RPM with the
following formula:
where
Vmin
= 1/65,536 counts/sample or steps/sample
Ts
= sample period in seconds per sample
60 = number of seconds in a minute
R
= counts or steps per revolution
or
You also can calculate the minimum velocity using the formula shown in
the
For a typical servo axis with 2,000 counts per revolution operating at a
250 µs update rate, the minimum RPM increment is
or
You can calculate the maximum velocity in RPM with the following
equation:
where
Vmax
= 20 MHz for servos
8 MHz for steppers on a NI 7350 controller
4 MHz for steppers on a NI 7330, NI 7340, or NI 7390
motion controller
R
= counts/steps per revolution
minimum RPM
Vmin
1
Ts
-----
×
60
×
1
R
---
×
=
minimum RPM
MIN
1
R
---
×
=
1
65,536
----------------
1
250
µ
s
----------------
×
60
1
2000
------------
×
×
0.00183105 RPM
=
3.662109
1
2000
------------
×
0.00183105 RPM
=
maximum RPM
Vmax
60
×
1
R
---
×
=
