Mitsubishi Electric MELSEC-L LD75D, User Manual

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(b) Pulse train output from the LD75
1.
As shown in the figure below, the pulse frequency increases as the motor accelerates. The pulses
are sparse when the motor starts and more frequent when the motor speed comes close to the
target speed.
2.
The pulse frequency stabilizes when the motor speed equals the target speed.
3.
The LD75 decreases the pulse frequency (sparser pulses) to decelerate the motor 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 motor.
This difference, called "the stop settling time", is required for gaining a stopping accuracy.
(2) Movement amount and speed in a system using worm gears
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)
R: Deceleration ratio
V: Movable section speed (mm/s)
N: Motor speed (r/min)
K: Position loop gain (1/s)

: Deviation counter droop pulse amount
P0: OP (pulse)
P: Address (pulse)
Speed V Pulse droop
amount
Pulse
distribution
Servomotor
speed
Accel-
eration
Decel-
eration
Time t
Stop
settling time
Pulse train Rough Dense Rough
V
R
L
P0
P
Pulse encoder
(PLG)
Workpiece
Worm gear
Table
Servomotor