Mitsubishi MELSEC-A A1SD71-S2 User Manual page 35

3.
SPECIFICATIONS
MELSEC-A
Zero return data is explained below:
(1) Zero return direction
Specifies the direction for zero return.
IMPORTANT
I
Zero return is controlled according to the zero return direction and
speed. Deceleration is started when an actuator is operated. Always
ensure that the zero return direction is correct for the drive system used.
(2)
Zero return methods
There are three kinds of zero return methods:
The pulse generator (PG) zero-phase signal method
Mechanical stop (1) (caused by dwell timer time)
Mechanical stop
(2)
(caused by a signal from the drive unit)
(a) Method by the pulse generator (PG) zero-phase signal method
This method of stopping by a zero-phase signal from the PG is shown
in Fig. 3.1 1.
A PG with a zero-phase signal is necessary. (Refer to Fig. 3.1 2.)
,
Zero return speed
Deceleration
by
near-point dog ON
\cr
Creep speed
I
Near-Point dog
M
Drift (in accordance with the drive)
,
. .
I
u u
U U I U
e u s
t the actuator so that the near-point dog OFF position is
near the center of the zero-phase signal HIGH.
If the near-point dog i s turned ON when the zero-phase signal
is LOW. the zero return stop position causes an error equal
to
one rotation of the servo motor.
ON
OFF
Zero-phase signal
U J
LJ
L
One servo motor rotation
(one PG rotation)
Fig. 3.11 Zero return Using a PC CPU Zero-Phase Signal
~ ~ ~~ ~~ ~~~~~~~~ ~~~
One PG rotation
n
i
PG zero-phase signal
Pulse generated
by
PG
I
Fig.
3.12
Feedback Pulse Pattern
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