
4.SERVO FUNCTION DETAILS B-65270EN/05
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(8) Other specifications to note regarding the fine acc./dec. function
• Advanced preview control and fine acc./dec. can be used
together. (The time constants before and after advanced preview
interpolation, and the fine acc./dec. time constant are effective.)
• If FAD is set, then the G05 P10000 command is issued with
HPCC, FAD is disabled.
• Using the FAD function increases the position error as follows:
- For FAD bell-shaped
(pulses) inceraseDeviation
+×
××
1
2
(ms)constant timeFAD
(mm)unit Detection 100060
(mm/min) Feedrate
- For FAD linear type
(pulses) inceraseDeviation
+
+
×
××
1
2
1(ms)constant timeFAD
(mm)unit Detection 100060
(mm/min) Feedrate
Example)
When feed operation is performed using F1800 with a position
gain of 30 (1/s) and a detection unit of 0.001 mm, the position
error is normally expressed as follows:
(pulses)deviation Normal
(mm)unit Detection (1/s)gain Position 60
(mm/min) Feedrate
××
)(1000
001.00360
1800
pulses=
××
=
When the FAD function (FAD bell-shaped) is used with the time
constant set to 64 ms, the deviation increases as follows:
(pulses) inceraseDeviation
)(9901
201.0100060
641800
pulses=+×
××
When FAD is used, the entire deviation is then obtained as
follows:
Deviation when FAD is used (pulses) = 1000 + 990
= 1990 (pulses)
The combined use of the FAD function and the feed-forward function
does not increase the position error so much as expected, because the
feed-forward function decreases a delay against the command. When
the FAD function is used alone, however, a higher error
overestimation level must be set, considering the increase in the
deviation.