Chapter 4
What You Need to Know about Moves
©
National Instruments Corporation
4-9
You can calculate the minimum acceleration increment with the following
formula:
where
Amin
= 1/65,536 counts/sample
2
or steps/sample
2
Ts
= sample period in seconds per sample
For a typical servo axis with 2,000 counts per revolution operating at the
250 µs update rate, calculate the minimum acceleration/deceleration
increment using the following equation:
You can calculate the maximum acceleration/deceleration using the
following equation:
where
Amax
= 32 counts/sample
2
Ts
= sample period in seconds per sample
and is constrained according to the following equations:
acceleration
≤
256
×
deceleration
deceleration
≤
65536
×
acceleration
NI 73
xx
Acceleration in RPS/s
Acceleration and deceleration values in RPS/s are converted to an internal
16.16 fixed-point format in units of counts/sample
2
or steps/sample
2
before
being used by the trajectory generator.
Table 4-3 shows the minimum and maximum acceleration update rates in
counts/sec
2
.
minimum acceleration/deceleration
Amin
1
Ts
-----
2
×
=
1
65536
---------------
1
250
µ
s
---------------
2
×
244 counts/second
2
=
maximum acceleration/deceleration
Amax
1
Ts
-----
2
×
=
