Absolute Position Detection System; Outline; Features; Restrictions - Mitsubishi Electric Melservo MR-J3-A Instruction Manual

14. ABSOLUTE POSITION DETECTION SYSTEM

14. ABSOLUTE POSITION DETECTION SYSTEM
CAUTION

14.1 Outline

14.1.1 Features

For normal operation, as shown below, the encoder consists of a detector designed to detect a position within
one revolution and a cumulative revolution counter designed to detect the number of revolutions.
The absolute position detection system always detects the absolute position of the machine and keeps it
battery-backed, independently of whether the general-purpose programming controller power is on or off.
Therefore, once the home position is defined at the time of machine installation, home position return is not
needed when power is switched on thereafter. If a power failure or a fault occurs, restoration is easy.
General purpose programmable
controller
CPU
Positioning module
I/O module

14.1.2 Restrictions

The absolute position detection system cannot be configured under the following conditions. Test operation
cannot be performed in the absolute position detection system, either. To perform test operation, choose
incremental in parameter No.PA03.
(1) Speed control mode, torque control mode.
(2) Control switch-over mode (position/speed, speed/torque, torque/position).
(3) Stroke-less coordinate system, e.g. rotary shaft, infinitely long positioning.
(4) Changing of electronic gear after home position setting.
(5) Use of alarm code output.
If an absolute position erase alarm (AL.25) or absolute position counter warning
(AL.E3) has occurred, always perform home position setting again. Not doing so
can cause runaway.
POINT
When configuring an absolute position detection system using the QD75P/D PLC,
refer to the Type QD75P/QD75D Positioning Module User's Manual
QD75P1/QD75P2/QD75P4, QD75D1/QD75D2/QD75D4 (SH (NA) 080058).
Pulse train
(command)
Current
position
data
Input
Output
Servo motor
1 pulse/rev Accumulative
Within-one-revolution counter
(Position detector)
Servo amplifier
Home position data
EEPROM memory
LSO
1XO
Backed up in the
case of power failure
Detecting the
number of
revolutions
MR-J3BAT
Battery
14 - 1
Current
position
data
LS 1X
Detecting the
position within
one revolution
High speed serial
communication