Chapter 4 What You Need to Know about Moves
© National Instruments Corporation 4-7 NI-Motion User Manual
and is constrained by acceleration/deceleration according to the following
equation:
velocity ≤ (65,536 × deceleration) – acceleration
where velocity is in counts/sample and acceleration and deceleration are in
counts/sample2.
From the example, the maximum RPM is
RPM values stored in onboard variables are in double-precision IEEE
format (f64).
NI 73xx Velocity in Counts/s or Steps/s
Velocity values in counts/s or steps/s are also converted to the internal
16.16 fixed-point format in units of counts or steps per sample (update)
period before being used by the trajectory generator. Although the motion
controller can control velocity to 1/65,536 of a count or step per sample, it
is impossible to load a value that small with the Load Velocity function, as
shown in the following formula:
where Vmin = 1/65,536 counts/sample or steps/sample
Ts = sample period in seconds per sample
Even at the fastest update rate, Ts =6 2.5 ×10–6
The Load Velocity function takes an integer input with a minimum value of
1 count/s or step/s. You cannot load fractional values. If you need to load a
velocity slower than one count or step per second, use the Load Velocity
in RPM function.
20 106
×()60 1
2,000
-------------


×× 600,000 RPM=
Velocity in counts or steps/s Vmin 1
Ts
-----


×=
1
65,536
----------------

 1
62.5 10 6–
×
---------------------------


×0.244 counts or steps/s=