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6
1-5
Control System Configuration
The following block diagram shows a control system for a servomotor driver.
The Position Control Unit is arranged in a semiclosed-loop system.
C500-NC222-E PCU
Control voltage
output
+10 V
Servomotor driver
Servomotor
Position
Tachogenerator
Position feedback
Rotary encoder
CW limit
Origin
CCW limit
Emergency stop
External interrupt
Teaching Box
C500-TU002-E
Memory
D/A
convertor
(16 bits)
Counter
Extrnal input
interface
T
eaching Box–
External Display
interface
M/D (Motor Driver)
connector
Peripheral
connector
MPU
PC
PC bus interface
EXT–IN
connector
–10 V
Speed feedback
Control Inputs
1-6
Control System Principles
Control systems can be quite simple or relatively complex. The most basic is
an open-loop system, in which a particular operation is carried out, according
to programmed instructions, but in which no feedback is provided for auto-
matic adjustments.
In a closed-loop system, PC controls an external process without human in-
tervention. The servomotor provides direct feedback so that actual values (of
positions, speeds, and so on) are continuously adjusted to bring them more
closely in line with target values. The digital feedback signals are commonly
transmitted to a digital-to-analog converter to complete the feedback loop,
thereby permitting automated control of the process.
The C500-NC222-E Position Control Unit is designed for use in a semi-
closed-loop system. A semiclosed-loop system is similar to a closed-loop
system, except that feedback is provided by a tachogenerator and a rotary
encoder rather than directly by the servomotor. This system, which also in-
Open-loop Systems
Closed-loop Systems
Semiclosed-Loop Systems
Control System Principles
Section 1-6