Mitsubishi Electronics MR-J2S- A Examples of use MELSEC-A1S A1SD71 Instructions, Abs

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.

Home position

Machine home

Machine home position (operation home position)

Home position

position

Programmable

Programmable

controller coordinate

0 10000

50000

controller coordinate

50000

10000

0

system

system

ABS

20000

0

50000

ABS

50000

0

20000

coordinate

Direction in which

Direction in which

coordinate

address increases

address increases

system

system

More than 1 revolution

More than 1 revolution

of motor shaft

of motor shaft

a) If revolution direction parameter (Pr. 14)

0

b) If revolution direction parameter (Pr. 14)

1

(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				Home position
Programmable
controller coordinate			0 10000		50000
system
ABS
		20000	0		50000
coordinate	ABS coordinate				Direction in which
system	value error occurs				address increases
	if power is turned
	on within this range			Absolute position data can be
				detected

					Machine
			Home position		home position
Programmable
controller coordinate		50000		10000	0
system
ABS		50000			0	20000
		Direction in which
coordinate						ABS coordinate
		address increases
system
						value error occurs
						if power is turned
	Absolute position data can be					on within this range
	detected

a) If revolution direction parameter (Pr. 14) 0

b) If revolution direction parameter (Pr. 14) 1

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