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BNJ 30703

Hanani bt Abd Wahab

Why do we study control systems?

What do these two have in common?

• 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”

Tornado Boeing 777

Controlled vs Uncontrolled

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Controlled vs Uncontrolled What is Control?

Control is a term that describes the process of forcing a system to behave in a desired way in order to achieve certain objective(s)/goal(s).

Control is the process of making a system variable adhere to a particular value, called the reference value.

What is Control System?Control system is a group of components which maintains desired results (goals) by manipulating the value of another variable in the system.

Goals (Desired results)

� Stability: system maintains desired operating point� Performance: system responds rapidly to changes� Robustness: system tolerates perturbations in dynamics

SenseVehicle Speed

ComputeControl “Law”

ActuateGas Pedal/

Brake

How to Control?

Control = Sensing + Computation + Actuation

In Feedback “Loop”

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Feedback Control SystemIn general

Main Components:• Plant: Process + Actuator• Controller• Sensor• Disturbance

Room Temperature Control

More Examples

� Control System in Nature

� Historical Examples

� Modern Examples

Control is “the hidden technology that you meet every day”

Control Systems in Nature� Pancreas:

� regulate blood sugar.

� Adrenalin� automatically generated to increase heart-rate and

oxygen intake in times of flight.

� Eyes� able to follow a moving object.

� Hand: � able to pick up an object and place it at a

predetermined location

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Historical Examples� Ancient Greece [1 – 300 BC]: water float

regulation, water clock, automatic oil lamp.� 17th Century: Cornelis Drebbel – temperature

control.� 18th Century: James Watt – Flyball governor� Late 19th Century to mid 20th Century:

Development of “Classical Control Theory”� 1960’s – present “Modern Control Theory”

Flyball Governor� Regulate speed of steam engine � Reduce effects of variations in load

(disturbance rejection)� Major advance of industrial revolution

Boulton-Watt steam engine

Balls fly out as speed increases,

Valve closes,slowing engine

http://www.heeg.de/~roland/SteamEngine.html

Flyballgovernor

Steamengine

Modern Examples

� Control System in Transportation System

� Control in Process Industry

� Control in Manufacturing Industry

� Control in Home

Control in Transportation

� Automotive: Engine regulation, active suspension, anti-lock braking system (ABS).

� Steering of missiles, planes, aircrafts and ships at sear.

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Control in Process Industry� In the process industries, control is used to

regulate level, pressure and temperature of refinery vessel.

� In steel rolling mill, the position of the rolls is controlled according to the measure of thickness of the steel coming off the finishing line.

Control in Manufacturing Systems

Control in Home� CD Players, the position of the laser spot in

relation to the microscopic pits in a CD is controlled.

� Video Recorder, the tracking of the record and play back head is controlled by controlling the velocity of the tape.

� Air conditioning system uses thermostat and control the temperature in the room.

Control in Home

CD Player

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Open-loop vs. Closed-loop� An open-loop control system utilizes an actuating

device to control the process directly without using feedback.

Missile launcher system

� A closed-loop control system uses a measurement of the output and feedback of the output signal to compare it with the desired output (reference or command).

Open-loop vs. Closed-loop

Control is “the hidden technology that you meet every day” Why do we study control systems?

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SummaryGoals (Desired results)

� Stability: �system maintains desired operating point

� Performance: �system responds rapidly to changes

� Robustness: �system tolerates perturbations in dynamics

� Main References :� Ogata K., Modern Control Engineering, Prentice Hall,

New Jersey, 2002 Fourth Edition.

� Others References :� J. Dorf, Modern Control Engineering, Addison Wesley

Publishing , 2004.� Norman S. Nise Control System Engineering, The

Benjamin Cummings Publishing Co. Inc. , 2004 Fourth.Edition,

� Introduction to Matlab 7 for Engineers, McGraw.HillInternational Edition, 2005