
B-65270EN/05 3. αiS/αiF/βiS SERIES PARAMETER ADJUSTMENT
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<2> Velocity feed-forward adjustment
When feed-forward is enabled, the time required for positioning
can be reduced, but a swell may occur due to insufficient velocity
loop response immediately before machining stops. A swell can
be reduced by an increased velocity loop gain, but there is an
upper limit on the velocity loop gain. So, adjust the velocity
feed-forward coefficient to reduce a swell for positioning time
reduction.
The default settings cause a swell immediately before machining
stops (Fig. 3.3.3 (f)). The swell can be reduced by increasing the
velocity feed-forward coefficient (Fig. 3.3.3 (g)).
n optimum is
achieved
when the
swell here is
reduced.
swell is
observed
immediately
before
machining stops.
Fig. 3.3.3 (g) After velocity feed-
orward
adjustment
FAD: 64 ms
Feed-forward: 98.5%
Velocity feed-forward coefficient: 250%
Fig. 3.3.3 (f) Before velocity feed-
orward
adjustment
FAD: 64 ms
Feed-forward: 98.5%
Velocity feed-forward coefficient: 100%
<3> Fine adjustment of feed-forward
Reduce the time required for positioning by making a fine
adjustment of the feed-forward coefficient. If the feed-forward
coefficient is not sufficiently large (Fig. 3.3.3 (h)), increase the
feed-forward coefficient by about 0.5%. If the feed-forward
coefficient is too large (Fig. 3.3.3 (i)), decrease the feed-forward
coefficient by about 0.5%.
Fig. 3.3.3 (h) When the
eed-
orward coefficient
is too small
FAD: 64 ms
Feed-forward: 98%
elocit
feed-forward coefficient: 250%
Fig. 3.3.3 (i) When the
eed-
orward coefficient
is too high
FAD: 64 ms
Feed-forward: 99%
elocit
feed-forward coefficient: 250%
If the position
feed-forward coefficient is
too large, an overshoot
occurs immediately
before machining stops.
If such an overshoot is
allowed from the
viewpoint of precision, the
time required for
positioning is reduced.
If the feed-forward
coefficient of the
position loop is too
small, an undershoot
occurs, resulting in a
longer time
.