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Control Systems EngineeringCourse
Lecture 1
Introduction
Azeddien Mo. Salah Kinsheel
1.1 Introduction
In recent years, control systems have assumed anincreasingly
important role in the development and
advancement of modern civilization and technology.Practically
every aspect of our day-to-day activities isaffected by some type
of control systems. Controlsystems are found in all abundance in
all sectors ofindustry, such as quality control of
manufacturedproducts, automatic assembly line, machine-tool
control,space technology, robotics, weapon systems, powersystems,
communication, chemical plants,nanotechnology and more others. Even
social andeconomic systems may approached from the theory of
automatic control.
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1.2 Definitions:
System:An interconnection of elements and devices for
a desired purpose.
A system is not limited to physical ones. The concept of
the system can be applied to any dynamic phenomena. It
could be mechanical , electrical, biological, economical,
chemical ..etc.
Examples: cooling system, steering system, nuclear
system, traffic system.
Control System:An interconnection of componentsforming a system
configuration that will provide
a desired response.
A typical control system, basically has an input,output and
controllable system.
Figure1: Simplified Block Diagram of Control system
1.2 Definitions:
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1.2 Definitions:
Examples of Automatic Control Systems:Water Level Control
system: Chemical Plants, Domestic
Water Tanks.
Temperature control system: Air conditioners,
refrigerators, Ovens.
Position Control System: CNC Machines, Robots, Lifts,
Conveyers.
Speed Control systems: Automobiles, Aircrafts.
Q1: what is the input and output of each of the abovecontrol
systems?
1.3 Control Systems Classification
Control systems can be classified on differentbases. Some of
these classifications are:Linearity: Linear and Non-Linear
Control
Systems.
Structure: Time Variant and Time InvariantControl Systems.
Continuity: Continues and Discrete ControlSystems Digital.
Configuration: Open Loop and Closed LoopSystems feedback.
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1.4 Linear Control Systems
Linear Control Systems: Is the system that satisfies
theproperties of superposition and homogeneity.
Output
InputX1 X2
Y2
Y1
Figure 2: Input output relationship in
Linear Systems
y=f(x)
The Superposition theoremIf y1=f(x1), y2=f(x2)
Then y1+y2=f(x1+x2)
The Homogeneity theoremIf y1=f(x1), then y2=f( kx1 )=ky1
Y=mx Linear
Y=mx+B Nonlinear! why?Y=x2 Nonlinear! why?
1.5 Time Varying Control System
Time Variant Control systems :is the system that hasone or more
parameters changing with time.
Are m, b ,k constants or vary with time?
Example of Time Variant systems :
Missile mass decreases as it consumes fuel in trajectory.
Robot has a variable inertia as its parts move.
)()()()( tutkxtxbtxm
Mass Out
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1.6 Continues and Discrete Control systems
Continues control system: is the system in which all
thecomponents are function of a continues time variable t.
Discrete data control system: is the system in which oneor more
of its variables are in form of pulse train ordigitally coded or
can only be obtained at a discrete timeintervals called sampling
time.
Figure 3: Continues and Discrete systems.
t t
x(t) x(t)
1.7 Open Loop and Closed Loop ControlSystems
Open Loop Control System: isthe system in which the outputhas no
effect on the control
action.
Closed Loop Control system: isthe system in which the
outputmeasurement is used todevelop the control action.
Figure 4: Open Loop andClosed Loop Control Systems
Control System
Control System+-
Feedback
Output
Output
Input
Input
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Review Questions
Why its important to study control systems?
Sketch one of the control systems around youand show how the
action (signal) propagatesfrom the input to the output.
Classify some of the control systems
around you.
Which of the following systems are linear?Y=3 x , y= 2 sin(t) ,
y=3x +4x , y=3 x cos(x)
Compare open loop and closed loop systems
