Design Outline Of Positioning Control System - Mitsubishi MELSEC-Q Series User Manual

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PRODUCT OUTLINE
1.2.2

Design outline of positioning control system

The following describes the outline of the operation of positioning control system, using
the QD72P3C3.
(1) Positioning control system using the QD72P3C3
Programmable
controller CPU
Program Read, write, etc.
Intelligent
function module
Monitor data read
parameter
interface
Initial setting/Auto refresh setting/Operation monitor
GX Configurator-PT
Figure 1.2 Outline of the operation of positioning control system using the QD72P3C3
(a) Positioning control operation using the QD72P3C3
Positioning module
QD72P3C3
Forward run
pulse train
Buffer
Reverse run
memory/
pulse train
XY device
1) The QD72P3C3 outputs a pulse train.
When the pulse train is output from the QD72P3C3, the deviation counter of
the drive unit accumulates the input pulses.
The D/A converter converts these accumulated pulses (droop pulses) into DC
analog voltage, which serves as a speed command for the servomotor.
2) The servomotor starts its rotation upon reception of the speed command from
the drive unit.
As the servomotor rotates, the pulse encoder (PLG) attached to the
servomotor generates feedback pulses in proportion to the rotation frequency.
The generated feedback pulses are fed back to the drive unit, and reduce the
droop pulses of the deviation counter.
The deviation counter maintains a certain number of droop pulses so that the
servomotor keeps its rotation.
3) When the QD72P3C3 stops the output of commanded pulse train, the
servomotor decelerates as the droop pulses of the deviation counter decrease
and finally stops when the droop pulse count drops to zero.
That is, the servomotor rotation speed is proportional to the pulse frequency,
while the servomotor rotation angle is proportional to the number of
commanded pulses output from the QD72P3C3.
When the movement amount per pulse is given, the overall movement amount
can be determined in proportion to the number of pulses in the pulse train.
The rotation speed (feed speed) of the servomotor, on the other hand, can be
determined by the pulse frequency.
1.2 Outline of Positioning Control and Count Operation
1.2.2 Design outline of positioning control system
Drive unit
Speed
command
Deviation
D/A
counter convertor
Interface
Feedback pulses
Servo motor
Servo
M
amplifier
PLG
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