National Instruments NI-Motion - Manual (Page 48)

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/sample
2 .
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 = 62.5
× 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 10
6 Ч ( ) 60
1
2,000
-------------
 
 
Ч Ч 600,000 RPM =
Velocity in counts or steps/s Vmin
1
Ts
-----
 
 
Ч
=
1
65,536
----------------
 
  1
62.5 10
6 – Ч
---------------------------
 
 
Ч 0.244 counts or steps/s =