Examples Of Use; Melsec-A1S (A1Sd71) - Mitsubishi Electric MELSERVO MR-J2S- A Instruction Manual

15. ABSOLUTE POSITION DETECTION SYSTEM

15.8 Examples of use

15.8.1 MELSEC-A1S (A1SD71)

(1) Instructions
The absolute coordinate system (programmable controller coordinate system) of the A1SD71 (AD71)
only covers the range in which the address increases (positive coordinate values) on moving away from
the machine home position (the position reached in the home position return operation). Therefore, if
the motor enters the range where the coordinate value is negative due to the load torque or a fall on a
vertical axis when the power is turned ON/OFF at a point near the machine home position, the system
fails to detect the absolute position. To prevent this problem, it is necessary to set the home position
(operation home position) for positioning in addition to the machine home position.
(a) The home position should be set in the direction in which the position address of the programmable
controller coordinate system increases on moving away from machine home position, as illustrated
below. Note that the home position for positioning must be more than one revolution of the servo
motor shaft from the machine home position.
If the address of the machine home position is changed to any value other than "0", the home
position should be set in the direction in which the position address increases on moving away from
the machine home position (machine home position after changing the home position address) and
at a point removed from the machine home position by more than one revolution of the motor shaft.
Machine home position
Programmable
controller coordinate
system
20000
ABS
coordinate
system
a) If revolution direction parameter (Pr. 14) 0
(b) In the range where the address decreases on moving away from the machine home position, do not
turn the power supply to the programmable controller or the servo amplifier, the servo-on
pushbutton switch, or the PC-RESET switch, ON/OFF. If any of these operations are attempted,
the ABS coordinate error (Y4B) is output since the absolute position cannot be detected.
Machine home position
Programmable
controller coordinate
system
ABS
20000
coordinate
ABS coordinate
system
value error occurs
if power is turned
on within this range
a) If revolution direction parameter (Pr. 14) 0
Home position
(operation home position)
0 10000 50000
0 50000
Direction in which
address increases
More than 1 revolution
of motor shaft
Home position
0 10000 50000
0 50000
Direction in which
address increases
Absolute position data can be
detected
Programmable
controller coordinate
system
ABS
coordinate
system
b) If revolution direction parameter (Pr. 14) 1
Programmable
controller coordinate
50000
system
50000
ABS
Direction in which
coordinate
address increases
system
Absolute position data can be
detected
b) If revolution direction parameter (Pr. 14) 1
15 - 21
Home position
50000 10000
50000
Direction in which
address increases
More than 1 revolution
of motor shaft
Machine
Home position home position
10000 0
0
ABS coordinate
value error occurs
if power is turned
on within this range
Machine home
position
0
0 20000
20000