Mitsubishi Electronics QD75P, QD75D user manual Pulse train output from the QD75

1PRODUCT OUTLINE

(b)Pulse train output from the QD75

MELSEC-Q

1)As shown in Fig. 1.3, the pulse frequency increases as the motor accelerates. The pulses are sparse when the motor starts and more frequent when the motor speed comes close to the target speed.

2)The pulse frequency stabilizes when the motor speed equals the target speed.

3)The QD75 decreases the pulse frequency (sparser pulses) to decelerate the 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 motor. This difference, called "the stop settling time", is required for gaining a stopping accuracy.

					Servomotor
Speed V	Pulse droop Pulse				speed
	amount	distribution
Accel-			Decel-			Time t
eration			eration
						Stop
						settling time
Pulse train Rough	Dense			Rough

Fig. 1.3 QD75 output pulses

(2) Movement amount and speed in a system using worm gears

Pulse encoder (PLG)

R

V

Workpiece Worm gear

Table

L

A	:	Movement amount per pulse (mm/pulse)
Vs :		Command pulse frequency (pulse/s)
n	:	Pulse encoder resolution (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)

Servomotor

P0

P

ε	: Deviation counter droop pulse amount
P0	: OP (pulse)
P	: Address (pulse)

Fig. 1.4 System using worm gears

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