
B-65270EN/05 3. αiS/αiF/βiS SERIES PARAMETER ADJUSTMENT
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(Rapid traverse positioning when fine acc./dec. is used)
For further reduction in the time required for rapid traverse
positioning, a delay due to position gain needs to be minimized. For
this purpose, feed-forward needs to be fully utilized. When
feed-forward is applied, the positional deviation decreases.
Accordingly, positional deviation convergence occurs more rapidly
after distribution, thus reducing the time required for positioning.
If feed-forward close to 100% is applied to normal acc./dec. (Fig.
3.3.3 (a) and (b)), a mechanical shock due to acceleration change at
the start and end of acc./dec., and a torque command vibration during
acc./dec. can pose a problem. To cope with this, the fine acc./dec.
function is available (Fig. 3.3.3 (c) and (d)).
FAD (Tf ≤ 64 ms) is used.
Feedrate
Time
Compared with linear
acceleration/deceleration,
acceleration change is
reduced, and a smooth
curve results. The time
required for positioning
can be reduced by feed-
forward.
T1 + Tf
Rapid traverse bell-shaped acceleration/deceleration
T2 > 64 ms
is used as well..
Feedrate
Time
If a second time constant
greater than 64 ms is
required, rapid traverse bell-
shaped acceleration/
deceleration is used (optional
function). The curve is made
smooth by inserting linear-
type FAD of 8 ms.
T1 + T2 + Tf
Fig. 3.3.3 (c) Fine acc./dec. (FAD) Fig. 3.3.3 (d) Rapid traverse bell-shaped acc./dec. + FAD
Fine acc./dec. increases the time required for command distribution by
a time constant. However, a time reduction in positioning achieved by
feed-forward is greater than this increase, so the time required for
positioning can be reduced in total. Thus, positioning can be speeded
up using fine acc./dec. The adjustment procedure is described in (3)
below.
(T1 + positioning time based on a position gain)
> (T1 + Tf + positioning time based on feed-forward)
A time constant up to 64 ms can be set for fine acc./dec. If a time
constant greater than 64 ms is required, use rapid traverse bell-shaped
acc./dec., and set 8 ms for linear-type fine acc./dec. (Fig. 3.3.3 (d)).
(3) Adjustment procedure
Make a rapid traverse positioning adjustment while viewing the ERR
(servo error amount). Adjust the measurement range so that the time
required for position deviation convergence within the in-position
width can be seen. At the same time, observe the TCMD to check that
the TCMD is not saturated. Before proceeding to the adjustment
described below, adjust the velocity loop gain according to Subsec.
3.3.1, "Gain Adjustment Procedure."
The measurement data of Fig. 3.3.3 (e) has been obtained under the
condition below. Fine acc./dec. and feed-forward are not used.
• Rapid traverse rate: 20000 mm/min
• Rapid traverse time constant: 150 ms
• Position gain: 30/s
• Travel distance: 100 mm