Mitsubishi Electric MELSEC-L LD75P User Manual page 566

(b) Preparation
Prepare the absolute position detection system taking care of the following.
Component
1) Servo amplifier
2) Servomotor
3) Detector cable
4) Programmable controller system
(2) Outline of absolute position detection data communication
As shown in the figure below (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 programmable controller 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.
Programmable controller system
LCPU
Current
position
change
564
• Use a Mitsubishi Electric General-Purpose AC Servo which has an absolute position detection
function (absolute position data transference protocol) equivalent to that of MR-J3-A).
• 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.
• Use a servomotor with absolute position detector.
Refer to the servomotor manual for details.
• Add a battery power connection cable (BAT/LG signal) for wiring the incremental detector cable.
Refer to the cable operation manual for details.
• Carry out the transmission and receiving of the absolute position detection data by the I/O
modules (input 3 points/output 3 points).
• As input/output modules, use I/O modules of required number of I/O points or the general-purpose
I/O function of the LCPU.
• Place the 3 points of input signals so that the  is the same among the input number 0 to
F. The same for the 3 points of output signals.
Pulse train
LD75
command
Current feed
value
Machine feed
value
I/O module
Input
Output
Servomotor
1 pulse/rev cumulative rotation
counter
Super condenser
Counter in one rotation
A.B.Z phase signal
Detector
Details
Servo amplifier
OP data
E 2 PROM memory
Current
LS0
position
1X0
Backup at
power OFF
LS
Speed
detection
Battery
Position
control/
speed
control
1X
Detection of
position in one
rotation
High-speed serial
communication