1. Topics Outline
• Introduction
• History of Automatic Control
• Classification of Control Systems
• Example of Control Systems
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2. Learning Objectives
At the end of the lessons, students should be able to:
• Understand the fundamental concepts automatic control systems in engineering
applications.
• Describe the related terms in control systems that will be used further in the next
chapters.
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3. Historical Background of Automatic Control
18th Century
James Watt’s
centrifugal
governor for the
speed control of a
steam engine
1922
Automatic
controllers for
steering ships by
Minorsky
1932
Nyquist developed a
simple procedure for
determining stability
of closed-loop
systems
1934
Design of relay
servomechanisms
by Hazen
1940s
Frequency-
response method
to design linear
closed-loop
systems
1940s-1950s
Root locus
method by Evans
Late 1950s
Initiate design one
of optimal system
1960s
Digital computers
were available,
leading to
development time
domain analysis
of complex
system, modern
control theory, etc
1960-1980
Optimal control
of both
deterministic and
stochastic systems
1980-Present
Developments in
modern control
theory centered
around robust
control, H∞
control, etc
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4. Importance of Automatic Control Systems
Why automatic
control systems
are important?
One of the
major element
in modern
manufacturing
& industrial
processes
Essential in
industrial operations
include controlling
pressure,
temperature,
humidity, viscosity
& flow in the
process industries
Reducing many
routines of
manual
operations
Able to attain
optimal
performance
of dynamic
systems
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5. Basic Terms and Definitions
Terms Definitions
Controlled variable • Quantity or condition that is measured and controlled.
• Output of the system
Manipulated variable Quantity or condition that is varied by the controller, to affect the value of the
controlled variable
Plants • Include a set of equipment, a set of machine parts functioning together
• Purpose: to perform a particular operation
• E.g. mechanical device, heating furnace, chemical reactor, spacecraft
Processes Any operation to be controlled is a process
Disturbances • A signal that tends to adversely affect the value of the output of a system
• Internal disturbance: generated within the system
• External disturbance: generated outside the system and is an input
Feedback control Reduce the difference between the output of a system and some reference input in
the presence of disturbances (unpredictable)
Systems A combination of components that act together and perform certain objective
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