Outline Design Of Positioning System - Mitsubishi Electric AJ65BT-D75P2-S3 User Manual

1 PRODUCT OUTLINE

1.1.4 Outline design of positioning system

PLC CPU
Program
Write,
read,
etc.
The outline of the positioning system operation and design, using the D75P2, is shown
below.
Master Positioning
module module D75P2
Forward run
RX,
pulse train
RWr
Buffer Set data
Reverse run
RY,
memory
pulse train
RWw
Write,
read, etc.
· SW1IVD-AD75P-E
· SW0D5C-AD75P-E
· AD75TU
Fig. 1.2 Outline of the operation of positioning system using D75P2
1) The D75P2 output is a pulse train.
When the pulse train is output, the pulses are cumulated with the deviation
counter. This pulse droop amount is changed into a DC analog voltage by the D/A
converter, and is used as the speed command.
2) Simultaneously with the start of motor rotation by the speed command from the
drive unit, feedback pulses proportional to the speed are generated by the pulse
encoder PLG, and the droop pulses in the deviation counter are subtracted.
The deviation counter maintains a set droop amount and the motor continues
rotating.
3) When the command pulse output from the D75P2 is stopped, the droop pulses in
the deviation counter decreases, and the speed slows. When there are no more
droop pulses, the motor stops.
In other words, the motor rotation speed is proportional to the designated pulse
frequency, and the motor rotation angle is proportional to the No. of output
command pulses.
Thus, if the movement amount per pulse is specified, the motor can be fed to a
position proportional to the No. of pulses in the pulse train. The pulse frequency
will be the motor speed (feedrate).
4) As shown below, the pulse train is rough during motor acceleration, and is dense
at the full speed. During deceleration, the pulse train becomes rougher, and
finally the pulse reaches 0. The motor stops with a slight delay in respect to the
command pulse.
This time difference is required to ensure the stopping precision, and is called the
stop settling time.
Drive unit
D/A
Devia-
converter
tion
counter
1 - 8
MELSEC-A
Servomotor
Speed
command
Servo
amplifier
Interface
Feedback pulse
M
PLG