Positioning By Ac Servo System; Advantages For Using An Ac Servo System - Mitsubishi Electric Melsec FX Series Beginners Manual

Advantages for using an AC servo system

2

Positioning by AC Servo System

2.1 Advantages for using an AC servo system
With an AC servo system, positioning can be performed by many diversified methods. Typically, a
position controller, servo amplifier and servo motor are required for positioning with an AC servo sys-
tem. The representative servo system configuration is shown below.
Positioning
controller
The positioning controller
generates a specified quantity
of forward rotation (or reverse rotation)
pulses at a specified frequency.
Fig. 2-1: Block diagram of an AC servo system
In the latest AC servo systems, conventional weak points have been improved as follows:
● Although the latest systems are completely digital, they are equipped with parameters in
conformance to diversified mechanical specifications and electrical specifications so that simple
set-up is possible.
● As frequent operation is enabled by a low inertia motor, the maximum torque is increased and
the system can be applied to a wide variety of machines.
● The latest systems are equipped with an auto tuning function, with which the servo amplifier
automatically detects the load inertia moment and adjusts the gain. This is possible even if the
load inertia moment is unknown.
● The command communication cycle from the controller to the servo amplifier is improved for
synchronization accuracy and better speed/positioning accuracy.
● The latest systems also allow for long-distance wiring, reduced noise resistance, and simplified
wiring.
The top advantages to using an AC servo system are described below.
Compact and light servo
system
In the FA workplace, a down-
sized AC servo system occu-
pying less space is beneficial.
FX Positioning Control Systems
Commercial
Converter
power supply
AC DC
Command
pulse
Deviation
counter
Robust servo system
In accordance with severe
operation conditions, a
tougher AC servo system is
often required.
Servo amplifier
Smoothing
circuit
DC DC
Speed
command
Current
PWM (pulse width
control modulation control
The command pulse number is
subtracted by the feedback pulse
number, and the speed command to
drive the servo motor is made from the
deviation (accumulated pulse number).
When the accumulated pulse number
becomes 0, the servo motor stops.
Easy servo system
AC servo systems are easier
to handle than hydraulic
equipment. Easy systems are
also flexible for new staff.
Positioning by AC Servo System
Servo
motor
Inverter
AC SM
PLG
Feedback
current
Feedback
pulse
The servo motor is equipped with a
built-in encoder (pulse generator),
dedicated to high speed response, and
suitable for positioning control.
Good cost performance
servo system
An AC servo system with
good cost performance
saves a company in overall
engineering costs.
Encoder
210010da.eps
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