Precautions For Home Position Return - Mitsubishi Electric HG-MR Instruction Manual

APPENDIX
App. 5.8 Precautions for home position return
When a general positioning unit is used, the sequence of events is as shown in the following figure.
(1) When determining the on duration of the proximity dog, consider the delay time of the control section
and the deceleration time so that the creep speed is attained. If the proximity dog signal switches off
during deceleration, precise home position return cannot be performed.
Travel distance L in the chart can be obtained by equation 5.28.
1
1
L = • V • t • +
1 1 1
60
On duration of the proximity dog L
in equation 5.29.
L > L ······················································································································· (5.29)
D 1
where,
V , V : As shown in the chart [mm/min]
1 2
t , t : As shown in the chart [s]
1 d
L : As shown in the chart [mm]
1
L : As shown in the chart [mm]
D
(2) Set the end (off position) of the proximity dog signal at the middle of two on positions (lows) of the zero
pulse signal. If it is set near either on position of the zero pulse signal, the positioning unit is liable to
misdetect the zero pulse signal. In this case, a fault will occur, e.g. the home position will shift by one
revolution of the servo motor.
Home position return speed V
Zero pulse signal
When determining the on duration of the proximity dog,
consider the deceleration time so that the speed reaches
the creep speed.
Home position
return speed V
Control delay
time t
1
1
V
1 -
• V • t • 2
1 d
120
V
1
[mm] must be longer than L
D
1
Proximity dog on starts deceleration
Creep speed V
Proximity dog
On Off
Travel distance until reaching the
creep speed after proximity dog is
1
detected L
1
Creep speed V
Deceleration
time t
d
On duration of the
proximity dog L
D
2
1
+ • V • T ················································· (5.28)
1 P
60
obtained by equation 5.28, as indicated
1
App. - 22
2
Considering the variations of the proximity dog
operation, adjust the proximity dog so that it
switches off at the middle during the zero
pulse signal on.
2