Absolute (Abs) Encoders - Omron CS1W-MCH71 MOTION CONTROL UNIT - 09-2004 Manual

Absolute (ABS) Encoders

8-5 Absolute (ABS) Encoders
Overview
Applicable Absolute
Encoders
3. After the origin proximity input signal is turned OFF, the speed is reduced
at the first rise of phase-Z.
4. The machine origin will be defined after the axis travels back for the excess
distance at the origin search creep speed.
• If the final travel distance has been specified, the machine origin will
be defined after the axis travels back for the specified distance.
• If the reference origin offset value has been set in the system param-
eter, the specified value will be the machine coordinate of the stopping
position.
• The origin search operation and alarm occurrence will vary depending
on the input timings of limit input signal, origin proximity input signal,
and phase-Z, origin search start direction, and the position of the work
when executing the origin search.
The absolute encoder retains absolute data by using the backup battery when
the MC Unit is turned OFF. When PLC (MC Unit) is turned ON again, the
absolute data is read from the absolute encoder to determine the present
position. Therefore, once an origin is set, no origin search will be required
after the power is turned ON (required for INC encoders).
The absolute position can be detected using the absolute encoder on the
motor with a semi-closed loop system. The detector is composed of an
encoder detecting the absolute position within one rotation and a counter that
counts the number of rotations.
The ABS data that is stored in the ABS encoder consists of [the number of
rotations from the absolute reference position (M)] and [the position within one
encoder rotation (PO)]. This ABS data is read as serial data when the power
for the system is turned ON. After that, the operation of an absolute encoder
will be the same as that of an incremental encoder.
The absolute position PE can be found using the following expression:
PE = M × R + PO
• Number of rotations from the absolute reference position:M
• Number of pulses per one encoder rotation:
• The position within one encoder rotation:
The ABS encoder constantly holds the ABS data using battery even when the
power is OFF. Moreover, it updates the data when there is any data change.
The battery is connected to the battery connector of the Servo Driver.
The Servo Driver reads the absolute data when the power is turned ON. Addi-
tionally, the MC Unit reads the same data to calculate the absolute position to
set the machine coordinate system automatically.
The following Servomotors with absolute encoders that can be connected to
the MC Unit are provided:
OMRON W Series (R88M-W@@@@@S)
(R88M-W@@@@@T)
Section 8-5
R
PO
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