Control System Configuration And Principles; Servo System - Omron CS1W-MC221 - 02-2008 Operation Manual

Control System Configuration and Principles

1-4 Control System Configuration and Principles
1-4-1

Servo System

Semi-closed Loop System
Internal Operations of the
MC Unit
1,2,3...
12
The servo system used by and the internal operations of the MC Unit are
briefly described below.
The servo system of the MC Unit uses a semi-closed loop system. This sys-
tem is designed to detect actual machine movements by rotation of the motor
in relation to a target value. It computes the error between the target value
and actual movement, and zeroes the error through feedback.
Table
Ball screw
Semi-closed loop systems occupy the mainstream in modern servo systems
applied to positioning devices for industrial applications.
Commands to the MC Unit, speed control voltage to the servo driver, and the
feedback signals from the encoder are described in the next few pages.
Desired position
Error
counter
Pulse string
1. The error counter receives a target position in units of encoder pulses. This
is called a pulse string.
2. The error counter is directly connected to the D/A converter where the
pulses received by the error counter are converted to analog voltages.
These analog voltages are sent to the servo driver as the speed control
voltages.
Servomotor
Encoder
Actual
movement
Decelerator
Target value
Speed
control
voltage
D/A Servo driver
converter
Position feedback
Feedback pulses
Section 1-4
Position controller
Servomotor
Speed
feedback
Encoder