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© National Instruments Corporation
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
2
counts/sample
.
From the example, the maximum RPM is
(
×
20
10
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:
Velocity in counts or steps/s
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
1
×
--------------- -
65,536
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.
Chapter 4
1
6
)
×
×
60
------------ -
=
2,000
1
0.244 counts or steps/s
-------------------------- -
=
6 –
×
62.5
10
4-7
What You Need to Know about Moves
600,000 RPM
1
×
Vmin
---- -
=
Ts
–6
NI-Motion User Manual
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