Mitsubishi A1SD75M3 User Manual page 31

1 PRODUCT OUTLINE
Positioning
module
Speed = Pulse frequency
Movement amount = No. of pulses
Feedback pulses =
Pulses generated by detector
The principle of "position control" and "speed control" operation is shown below.
Position control
The total number of pulses in a pulse train required to move the designated distance
is obtained in the following manner.
Total number of
pulses in a pulse
train required to
move designated
distance
* The No. of pulses required for the servomotor to rotate once is the "pulse encoder
resolution" described in the servomotor catalog specification list.
When this total number of pulses in a pulse train is issued from the AD75 to the servo
amplifier, control to move the designated distance can be executed.
The machine side movement amount when one pulse is issued to the servo amplifier is
called the "movement amount per pulse". This value is the min. value for the workpiece
to move, and is also the electrical positioning precision.
Speed control
The above "total number of pulses in a pulse train" is an element required for
movement distance control, but when carrying out positioning control or speed
control, the speed must also be controlled.
This "speed" is controlled by the "pulse train frequency".
Servo
amplifier
Feedback pulse
Fig.1.1 Relationship between position control and speed control
POINT
The AD75 controls the position with the "total number of pulses in a pulse train",
and the speed with the "pulse train frequency".
Designated distance
Movement amount of machine (load)
side when motor rotates once
Pulse frequency
[pps]
Servomotor
Detector
(Pulse
encoder)
1 - 9
MELSEC-A
No. of pulses required
for servomotor to rotate
once
This area is the total
No. of commanded
pulse train.
A
ta td
0.4 1.2 0.4
Movement amount t = 2
(s)