Servo System Principles - Omron TJ2-MC64 Hardware Reference Manual

System philosophy
2.3

Servo system principles

The servo system used by and the internal operation of the TJ2-MC64 are
briefly described in this section.
2.3.1 Semi-closed loop system
The servo system of the TJ2-MC64 uses a semi-closed or inferred closed
loop system. This system detects actual machine movements by the rotation
of the motor in relation to a target value. It calculates the error between the
target value and actual movement, and reduces the error through feedback.
2.3.2 Internal operation of the TJ2-MC64
Inferred closed loop systems occupy the mainstream in modern servo
systems applied to positioning devices for industrial applications. The figure
shows the basic principle of the servo system as used in the TJ2-MC64.
1. The TJ2-MC64 performs actual position control. The main input of the
controller is the Following Error, which is the calculated difference
between the demand position and the actual measured position.
2. The Position Controller calculates the required speed reference output
determined by the Following Error and possibly the demanded position
and the measured position. The speed reference is provided to the
Servo Drive.
3. The Servo Drive controls the rotational speed of the servo motor
corresponding to the speed reference. The rotational speed is
proportional to the speed reference.
4. The rotary encoder generates the feedback pulses for both the speed
feedback within the Servo Drive speed loop and the position feedback
within the TJ2-MC64 position loop.
The labels in the figure are:
A. TJ2-MC64.
B. Servo system.
C. Demand position.
D. Position control.
E. Speed reference.
HARDWARE REFERENCE MANUAL
fig. 15
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C
E
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D F
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B
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