Mitsubishi Electric MELSECQ Series User Manual page 21

1 PRODUCT OUTLINE
Pulse encoder
(PLG)
Servomotor
1 - 5
Downloaded from ManualsNet.com
(b) Pulse train output from the QD70
1) As shown in Fig. 1.3, the pulse frequency increases as the servomotor
accelerates. The pulses are sparse when the servomotor starts and
more frequent when the servomotor speed comes close to the target
speed.
2) The pulse frequency stabilizes when the motor speed equals the target
speed.
3) The QD70 decreases the pulse frequency (sparser pulses) to
decelerate the servomotor before it finally stops the output.
There will be a little difference in timing between the decrease in the
pulse frequency and the actual deceleration and stopping of the
servomotor.
This difference, called "the stop settling time", is required for gaining a
stopping accuracy.
Speed V
Accel-
eration
Pulse train Rough
(2) Movement amount and speed in a system using worm gears
V
Workpiece
Table
P0
Fig. 1.4 System using worm gears
search engine
Pulse droop
amount Pulse
distribution
Decel-
eration
Dense Rough
Fig. 1.3 QD70 output pulses
A : Movement amount per pulse (mm/pulse)
Vs : Command pulse frequency (pulse/s)
n : Pulse encoder resolution (pulse/rev)
L : Worm gear lead (mm/rev)
Worm pear
R : Deceleration ratio
V : Movable section speed (mm/s)
L
N : Motor speed (r/min)
K : Position loop gain (1/s)
P
ε
: Deviation counter droop pulse amount
P0 : OP (pulse)
P : Address (pulse)
MELSEC-Q
Servomotor
speed
Time t
Stop
setting time
1 - 5