Table of Contents
Advertisement
1 PRODUCT OUTLINE
1.1.3 Outline design of positioning control system
Programmable controller
CPU
Read, write, etc.
Program
Intelligent
Monitor date read
function module
parameter
Initial setting /Auto rofresh setting/Monitor
GX Configurator-PT
Fig. 1.2 Outline of the operation of positioning control system using QD70D
1 - 5
The outline of the positioning control system operation and design, using the QD70D,
is shown below.
(1) Positioning control system using QD70D
Positioning module
QD70D
Forward run
pulse train
Buffer
Reverse run
memories
pulse train
/XY
device
(a) Positioning operation by the QD70D
1) The QD70D output is a pulse train.
The pulse train output by the QD70D is counted by and stored in the
deviation counter in the drive unit.
The D/A converter outputs an analog DC current proportionate to the
count maintained by the deviation counter (called "pulse droop"). The
analog DC current serves as the servomotor speed control signal.
2) The servomotor rotation is controlled by the speed control signal from
the drive unit.
As the servomotor rotates, the pulse encoder (PLG) attached to the
servomotor generates feedback pulses, the frequency of which is
proportionate to the rotation speed.
The feedback pulses are fed back to the drive unit and decrements the
pulse droop, the pulse count maintained by the deviation counter.
The motor keeps on rotating as the pulse droop is maintained at a
certain level.
3) When the QD70D terminates the output of a pulse train, the servomotor
decelerates as the pulse droop decreases and stops when the count
drops to zero.
Thus, the servomotor rotation speed is proportionate to the pulse
frequency, while the overall motor rotation angle is proportionate to the
total number of pulses output by the QD70D.
Therefore, when a movement amount per pulse is given, the overall
movement amount can be determined by the number of pulses in the
pulse train.
The pulse frequency, on the other hand, determines the servomotor
rotation speed (feed speed).
Drive unit
Speed
command
D/A
Deviation
converter
counter
Interface
Feedback pulse
MELSEC-Q
Servomotor
Servo
M
amplifiter
PLG
1 - 5
Advertisement
Table of Contents
