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14. ABSOLUTE POSITION DETECTION SYSTEM
14. ABSOLUTE POSITION DETECTION SYSTEM
CAUTION
If an absolute position erase (A.25) or an absolute position counter warning
(A
E3) has occurred, always perform home position setting again. Not doing so
can cause runaway.
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 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.
Also, the absolute position data, which is battery-backed by the super capacitor in the encoder, can be
retained within the specified period (cumulative revolution counter value retaining time) if the cable is
unplugged or broken.
LS
EEP-ROM memory
LSO
1XO
Controller
1X
Pulse train
command
Drive unit
Home position data
Backed up
in the case of
power failure
Serial
communication
High speed serial communication
Servo motor
Super capacitor
1pulse/rev Accumulative
revolution counter
Detecting the
number of
revolutions
Detecting the
position within
one revolutions
Position control
Speed control
Battery
Battery unit
Current
position data
RS-422/
RS-232C
Changing the
current position
data
Current
position data
Within-one-revolution counter
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 DRU parameter No.1.
(1) Stroke-less coordinate system, e.g. rotary shaft, infinitely long positioning.
(2) Changing of electronic gear after home position setting.