Specifications

1 - 9
(b) Pulse train output from the QD75
1) As shown in Fig. 1.3, 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 QD75 decreases the pulse frequency (sparser pulses) to decelerate
the motor before it finally stops the output.
There will be a little time delay 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.
Speed V
Pulse droop
amount
Pulse
distribution
Servomotor speed
Time t
Pulse train Rough RoughDense
Acceleration
Deceleration
Stop settling time
Fig. 1.3 QD75 output pulses
(2) Movement amount and speed in a system using worm gears
V
R
L
Table
Workpiece
Worm gear
Servomotor
Pulse encoder (PG)
A : Position detection unit (mm/pulse)
Vs : Command pulse frequency (pulse/s)
n : Number of pulse generator's slits
(number of pulses) (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)
ε : Deviation counter droop pulse amount
Fig. 1.4 System using worm gears