Mitsubishi Electronics QD75D Outline of absolute position detection data communication, Current

12 CONTROL SUB FUNCTIONS

MELSEC-Q

(2)Preparation

Prepare the absolute position detection system taking care of the following.

	Component	Details
1)	Servo amplifier	• Install the battery to the servo amplifier.
		• Validate the absolute position detection function of the
		servo amplifier.
		Refer to the servo amplifier manual for details.
2)	Servomotor	• Use a servomotor with absolute position detector.
		Refer to the servomotor manual for details.
3)	Detector cable	• Add a battery power connection cable (BAT/LG signal) for
		wiring the incremental detector cable.
		Refer to the cable operation manual for details.
4)	PLC system	• Carry out the transmission and receiving of the absolute
		position detection data by the I/O modules (input 3
		points/output 3 points).
		• Use the "16 point input module" and "16 point output
		module".

[2] Outline of absolute position detection data communication

As shown in Fig. 12.33 System block diagram, the detector comprises an encoder for detecting its position in one rotation in addition to the A, B, Z phase signal for position control in normal operation and a cumulative rotation counter for detecting the number of rotations.

The absolute position detection system detects the absolute position of the machine constantly and stores it with the backup of the battery irrespective of whether the PLC system power is turned ON/OFF. Thus, once the OP initial setting is carried out at the time of installation of the machine, the OPR is not required even when the power is later turned ON. The restoration can be carried out easily when an instantaneous power interruption or emergency stop occurs. In addition, because the absolute position data is backed up by a super condenser built in the detector, the absolute position data will be stored for a specified time even if the cable is disconnected or broken.

	PLC system	Pulse train			Servo amplifier
QCPU	QD75
		command		OP data
	Current feed value
				E2PROM memory	Current		Position
	Machine feed value			LS0			control/
					position
				1X0			speed
	I/O module			Backup at			control
				power OFF	LS	1X
	Input
Current					Speed	Detection of
						position in one
position					detection	rotation
	Output
change				Battery
	Servomotor
	1 pulse/rev cumulative rotation						High-speed serial
	counter		Super condenser				communication
	Counter in one rotation
	A.B.Z phase signal
			Detector

Fig. 12.33 System block diagram

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