Mitsubishi Electric MELSEC-L LD75D, User Manual

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The principle of "position control" and "speed control" operation is shown below.
(1) Position control
The total No. of pulses required to move the designated distance is obtained in the following manner.
When this total No. of pulses is issued from the LD75 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.
(2) Speed control
The "Total No. of pulses" mentioned above is invariably required for controlling the distance. For positioning or
speed control, the speed must be controlled as well.
The speed is determined by the frequency of pulses sent from the LD75 to the drive unit.
The LD75 controls the position with the "total No. of pulses", and the speed with the "pulse frequency".
Total No. of pulses
required to move
designated distance
=
Designated distance
Movement amount of machine (load)
side when motor rotates once
No. of pulses
required for motor to
rotate once
The No. of pulses required for the motor to rotate once is the "encoder resolution"
described in the motor catalog specification list.
Positioning
module Servo
amplifier Servo
motor
Detector
(Pulse
encoder)
Feedback pulses
Speed = Pulses frequency
Movement amount = No.of pulses
Feedback pulses =
Pulses generated by detector
A
ta
0.4 0.4 1.2
(s)
Pulse frequency [pulse/s]
This area is the total
No. of commanded
pulses.
td
Movement amount t = 2