Introduction to Control Systems:
Regulation and Control System
CONTENTS
Basic Concepts
 Control System Examples
 Control System Design

January 11, 2005
WHAT DO THESE TWO HAVE IN COMMON?

Tornado

Boeing 777
• Highly nonlinear, complicated dynamics!
• Both are capable of transporting goods and people over long distances
BUT
• One is controlled, and the other is not.
• Control is “the hidden technology that you meet every day”
• It heavily relies on the notion of “feedback”
3
DEFINITIONS
Control systems are an integral component of any industrial
society and are necessary to provide useful economic products for
society.
Control engineering is based on the foundation of feedback
theory and linear system analysis, and integrates the concepts of
network theory and communication theory. Therefore, control
engineering is not limited to any engineering discipline but is
equally applicable for aeronautical, chemical, mechanical,
environmental, civil, and electrical engineering. For example, quite
often a control system includes electrical, mechanical, and
chemical components.
BASIC CONCEPTS

System


Dynamic System



A collection of components which are coordinated together to
perform a function.
A system with a memory.
For example, the input value at time t will influence the output at
future instant.
A system interact with their environment through a controlled
boundary.
BASIC CONCEPTS

The interaction is defined in terms of variables.
i.
ii.
iii.
System input
System output
Environmental disturbances
SYSTEM VARIABLES




The system’s boundary depends upon the defined objective
function of the system.
The system’s function is expressed in terms of measured
output variables.
The system’s operation is manipulated through control input
variables.
The system’s operation is also affected in an uncontrolled
manner through disturbance input variables.
CONTROL SYSTEM



Control is the process of causing a system variable to conform
to some desired value.
Manual control
Automatic control (involving machines only).
A control system is an interconnection of components forming a
system configuration that will provide a desired system
response.
Input
Signal
Control
System
Energy
Source
Output
Signal
MANUAL VS AUTOMATIC CONTROL


Control is a process of causing a system variable such as
temperature or position to conform to some desired value or
trajectory, called reference value or trajectory.
For example, driving a car implies controlling the vehicle to
follow the desired path to arrive safely at a planned destination.
i.
If you are driving the car yourself, you are performing manual control of
the car.
ii.
If you use design a machine, or use a computer to do it, then you have
built an automatic control system.
RESPONSE CHARACTERISTICS

Transient response:


Steady-state response:


Gradual change of output from initial to the desired condition
Approximation to the desired response
For example, consider an elevator rising from ground to the 4th
floor.
BLOCK DIAGRAM


Component or process to be controlled can be represented by a
block diagram.
The input-output relationship represents the cause and effect of the
process.
Input

Process
Output
Control systems can be classified into two categories:
i.
Open-loop control system
ii.
Closed-loop feedback control system
CONTROL SYSTEM CLASSIFICATION

An open-loop control system utilizes an actuating device to control
the process directly without using feedback.
Desired Output
Response

Actuating
Device
Process
Output
A closed-loop feedback control system uses a measurement of the
output and feedback of the output signal to compare it with the
desired output or reference.
Desired
Output
Response
Comparison
Controller
Process
Measurement
Single Input Single Output (SISO) System
Output
CONTROL SYSTEM CLASSIFICATION
Missile Launcher System
Open-Loop Control System
CONTROL SYSTEM CLASSIFICATION
Missile Launcher System
Closed-Loop Feedback Control System
CONTROL SYSTEM CLASSIFICATION
Desired
Output
Response
Controller
Process
Measurement
Multi Input Multi Output (MIMO) System
Output
Variables
CONT.....
Static or Dynamic Systems: Static systems are
composed of simple linear gains or nonlinear
devices and described by algebraic equations,
and dynamic systems are described by
differential or difference equations.
 Continuous-time or Discrete-time Systems:
Continuous-time dynamic systems are
described by differential equations and
discrete-time dynamic systems by difference
equations.

PURPOSE OF CONTROL SYSTEMS
i.
Power Amplification (Gain)

ii.
Remote Control

iii.
Robotic arm used to pick up radioactive materials
Convenience of Input Form

iv.
Positioning of a large radar antenna by low-power rotation of a
knob
Changing room temperature by thermostat position
Compensation for Disturbances

Controlling antenna position in the presence of large wind
disturbance torque
HISTORICAL DEVELOPMENTS
i.
Ancient Greece (1 to 300 BC)

ii.
Cornellis Drebbel (17th century)

iii.
Temperature control
James Watt (18th century)

iv.
Water float regulation, water clock, automatic oil lamp
Flyball governor
Late 19th to mid 20th century

Modern control theory
WATT’S FLYBALL GOVERNOR
HUMAN SYSTEM
i.
Pancreas

ii.
Regulates blood glucose level
Adrenaline

Automatically generated to increase the heart rate and oxygen in
times of flight
iii.
Eye
iv.
Follow moving object
Hand
 Pick up an object and place it at a predetermined location
v.
Temperature


Regulated temperature of 36°C to 37°C
TEMPERATURE CONTROL

Figure shows a schematic diagram of temperature control of an electric furnace.
The temperature in the electric furnace is measured by a thermometer, which is
analog device. The analog temperature is converted to a digital temperature by
an A/D converter. The digital temperature is fed to a controller through an
interface. This digital temperature is compared with the programmed input
temperature, and if there is any error , the controller sends out a signal to the
heater, through an interface, amplifier and relay to bring the furnace
temperature to a desired value.
TRANSPORTATION
Car and Driver





Objective: To control direction and speed of car
Outputs: Actual direction and speed of car
Control inputs: Road markings and speed signs
Disturbances: Road surface and grade, wind, obstacles
Possible subsystems: The car alone, power steering system,
breaking system
TRANSPORTATION

Functional block diagram:
Desired
course
of travel +
Error
-
Driver
Steering
Mechanism
Automobile
Measurement, visual and tactile

Time response:
Actual
course
of travel
TRANSPORTATION

Consider using a radar to measure distance and velocity to
autonomously maintain distance between vehicles.

Automotive: Engine regulation, active suspension, anti-lock breaking
system (ABS)
Steering of missiles, planes, aircraft and ships at sear.

PROCESS INDUSTRY

Control used to regulate level, pressure and pressure of refinery
vessel.
Coordinated
control system
for a boilergenerator.

For steel rolling mills, the position of rolls is controlled by the
thickness of the steel coming off the finishing line.
MANUFACTURING INDUSTRY

Consider a three-axis control system for inspecting individual
semiconducting wafers with a highly sensitive camera
HOMES
i.
CD Players

ii.
The position of the laser spot in relation to the microscopic pits
in a CD is controlled.
Air-Conditioning System

Uses thermostat and controls room temperature.
CONTROL SYSTEM COMPONENTS
i.
System, plant or process

ii.
Actuators

iii.
Converts the control signal to a power signal
Sensors

iv.
To be controlled
Provides measurement of the system output
Reference input

Represents the desired output
GENERAL CONTROL SYSTEM
Disturbance
Set-point
or
Reference
input +
Controlled
Signal
Error
-
+
Controller
Feedback Signal
Manipulated
Variable
Actuator
Sensor
+
+
+
Process
Actual
Output
January 11, 2005
MODERN ENGINEERING APPLICATIONS OF
CONTROL


Flight Control Systems
 Modern commercial and
military aircraft are “fly by wire”
 Autoland systems, unmanned
aerial vehicles (UAVs) are
already in place
Robotics
 High accuracy positioning for
flexible manufacturing
 Remote environments: space,
sea, non-invasive surgery, etc.



Chemical Process Control
 Regulation of flow rates,
temperature, concentrations,
etc.
 Long time scales, but only crude
models of process
Communications and Networks
 Amplifiers and repeaters
 Congestion control of the
Internet
 Power management for wireless
communications
Automotive
 Engine control, transmission
control, cruise control, climate
control, etc
 Luxury sedans: 12 control
devices in 1976, 42 in 1988, 67
30
“The right half of the brain controls the left half of the body. This
means that only left handed people are in their right mind…”
THE END…