Mitsubishi GX Configurator-PT, User Manual

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MELSEC-Q
1 PRODUCT OUTLINE
(b) Pulse train output from the QD70
1) As shown in Fig. 1.3, the pulse frequency increases as the servo motor
accelerates. The pulses are sparse when the servo motor starts and
more frequent when the servo motor speed comes close to the target
speed.
2) The pulse frequency stabilizes when the motor speed equals the target
speed.
3) The QD70 decreases the pulse frequency (sparser pulses) to
decelerate the servo motor before it finally stops the output.
There will be a little difference in timing between the decrease in the
pulse frequency and the actual deceleration and stopping of the servo
motor.
This difference, called "the stop settling time", is required for gaining a
stopping accuracy.
Speed V Pulse droop
amount
Pulse
distribution
Servomotor
speed
Accel-
eration Decel-
eration Time t
Stop
setting time
Pulse train Rough Dense Rough
Fig. 1.3 QD70 output pulses
(2) Movement amount and speed in a system using worm gears
V
L
P0
P
Workpiece
Worm pear
Table
Pulse
generator
(PG)
Servomotor
A : Movement amount per pulse (mm/pulse)
Vs : Command pulse frequency (pulse/s)
n : No. of pulse generator slits
"
No. of pulses
"
(pulse/rev)
L : Worm gear lead (mm/rev)
R : Deceleration ratio
V
: Movable section speed (mm/s)
N : Motor speed (r/min)
K
: Position loop gain (1/s)
ε
: Deviation counter droop pulse amount
P0 : OP (pulse)
P
: Address (pulse)
Fig. 1.4 System using worm gears