Servo Amplifier And Servo Motor; Positioning Control In Accordance With Command Pulse; Deviation Counter Function - Mitsubishi Electric Melsec FX Series Beginners Manual

Components of Positioning Control and their Roles
3.2

Servo Amplifier and Servo Motor

The servo amplifier controls the movement quantity and the speed according to the commands given
by the positioning controller. The servo motor then transmits rotation to the drive mechanism after
receiving signals from the servo amplifier.
3.2.1

Positioning control in accordance with command pulse

In accordance with speed and position command pulses from the positioning controller, PWM (pulse
width modulation) control is performed by the main circuit of the servo amplifier in order to drive the
motor. The rotation speed and the rotation quantity are fed back to the amplifier from the encoder
attached to the servo motor.
3.2.2

Deviation counter function

The difference between the command pulses and the feedback pulses counted by the deviation
counter in the servo amplifier is called accumulated pulses.
While the machine is operating at a constant speed, the accumulated pulse quantity is almost
constant. During acceleration and deceleration, the accumulated pulse quantity changes more
dramatically.
When the accumulated pulse quantity becomes equivalent to or less than a specified quantity
(in-position set value) after command pulses have stopped, the servo amplifier outputs the
positioning complete signal.
The servo motor continues operation even after that. Then, when the accumulated pulse quantity
becomes 0, the servo motor stops.
The time after the servo motor outputs the positioning complete signal until it stops is called the stop
settling time.
Speed
Fig. 3-7: Positioning pattern
3 - 8
Command speed
Accumulated
pulses
Stop setting time
Servo Amplifier and Servo Motor
Motor speed
The accumulated pulse quantity is 0, and
positioning is completed
Time
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