
3. αiS/αiF/βiS SERIES PARAMETER ADJUSTMENT B-65270EN/05
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3.3.3 Rapid Traverse Positioning Adjustment Procedure
(1) Overview
The fine acc./dec. function applies a filter to each axis in the servo
software to reduce a shock associated with acc./dec. By combining the
fine acc./dec. function with feed-forward, high-speed positioning can
be achieved in rapid traverse. This section describes rapid traverse
positioning adjustment.
(2) High-speed positioning by a combination of fine acc./dec. and
feed-forward
(Rapid traverse positioning when fine acc./dec. is not used)
A servo loop not performing feed-forward has a delay equivalent to a
position loop gain. The time required for positioning after completion
of distribution from the CNC is four to five times the position gain
time constant (33 ms for 30 [1/s]) (133 to 165 ms for a position gain of
30). In normal rapid traverse, rapid traverse linear acc./dec. (Fig. 3.3.3
(a)) is used, so that acceleration changes to a large extent at the start
and end of acceleration. However, since feed-forward is not used,
acceleration change is made moderate by a position loop gain, and a
shock does not occur.
If a low linear acc./dec. time constant is set for high-speed positioning,
and a high position gain and feed-forward are set, the time required
for positioning is reduced, but a shock occurs. In this case, a shock can
be reduced by setting rapid traverse bell-shaped acc./dec. (optional
function) (Fig. 3.3.3 (b)).
Fig. 3.3.3 (a) Rapid traverse linear acc./dec. Fig. 3.3.3 (b) Rapid traverse bell-shaped
acc./dec.
Rapid traverse linear time constant (T1) only
Rapid traverse bell-shaped acc./dec. (T1+ T2)
T1
Feedrate
Time
cceleration change is
large, so a shock tends
to occur.
Feed-forward cannot
be applied.
Feedrate
Time
cceleration change is
reduced.
T1 + T2