Overview Of The Absolute Position Detection System; Transmission Procedure For Absolute Position Signal - Mitsubishi Electric MELSEC iQ-R-RD75P4 User Manual

Overview of the absolute position detection system

The detector comprises an encoder for the detection of position in one rotation in addition to the A, B, and Z phase signals for
the position control in normal operation and an accumulative revolution counter for the detection of 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 the state of the power supply to the programmable controller system. Therefore, once the OP
initial setting is performed at the time of the installation of the machine, no OPR is required even when the power is turned on
later. The restoration of the system can be performed easily even when an instantaneous power failure or an emergency stop
occurs.
In addition, because the absolute position data is backed up by a super capacitor in the detector, the absolute position data
will be hold for a specified time even if a cable is disconnected or broken.

Transmission procedure for absolute position signal

The following figure shows the overview of the absolute position signal transmission procedure between a servo amplifier and
a programmable controller system (CPU module, RD75, and I/O modules).
For details on the communication between the servo amplifier and programmable controller system, refer to the manual for
the servo amplifier used.
Errors during communication
• If a time-out occurs during communication, ABS transmission time out (Error code: 1949H) occurs.
• If transmission data causes a sum error, ABS transmission SUM (Error code: 194AH) occurs.
For corrective actions on errors, refer to the following.
Page 527 List of Error Codes
Servo amplifier
Absolute position detection request
Data transmission
Current position
data
I/O module
⋅
Servo ON signal
⋅
ABS transmission
mode
⋅
ABS request
⋅
ABS transmission
data ready
⋅
ABS bit 0
⋅
ABS bit 1
CPU module
[Dedicated
instruction]
Current position data
G.ABRST1
G.ABRST2
G.ABRST3
G.ABRST4
7 CONTROL SUB FUNCTIONS
7.7 Absolute Position Restoration Function
RD75
Current feed
Md.20
value
Machine feed
Md.21
value
265
7