SKEE 3133 Chapter 1 Revised

1SKEE 3133

CONTROL:SYSTEM MODELING &

SIMULATIONSKEE 3133SYSTEM MODELING AND

ANALYSIS

SKEE 3133 SYSTEM MODELLING & ANALYSIS: CHAPTER 1

Lecturer Section 1 Dr Fatimah Sham Ismail Section 2 PM Dr Zaharuddin Mohamed Section 3 Dr Salinda Buyamin / Dr Khairul

Hamimah Abas

Section 4 PM Zamani Md Zain Section 5 Dr Herman Wahid Section 6 Dr Shahdan Sudin


Synopsis

This course introduces the students to the fundamental ideas and definitions of control systems, open loop and close loop control systems, transfer functions and transient and steady state responses. Students will be taught how to obtain mathematical models of actual physical systems such as electrical, mechanical and electromechanical systems in the transfer function form. Methods of system representation such as block diagram representation and signal flow graphs will be examined. The students will also be exposed to techniques of analysing control systems performance and stability in time and frequency domains. Finally, an introduction to the design and analysis of control systems using MATLAB will also be given

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Learning Outcome

Apply the knowledge of basic control theory to describe the structure of control system design and control system representation

CO1 Apply the knowledge of mathematics, science and electrical

engineering to derive the mathematical models and transfer functions of electrical, mechanical, and electromechanical systems

CO2

Employ the transfer function of the control system to illustrate its performance and stability in time and frequency domains.CO3

Use MATLAB software in analysing control system performance and stability. CO4


Syllabus

Introduction to Control Engineering1 Mathematical Modelling: Laplace Transform, Transfer

Function, Electrical, Mechanical, Electromechanical, Liquid level

2 System Representation: Block diagram, Signal Flow

Graph3 Time Domain Analysis: Time Response, Steady-

state error, Routh-Hurwitz Stability Criterion4 Frequency Domain Analysis: Frequency response,

Bode plot, Stability, Steady-state error. 5


ReferencesNorman S. Nise, Control Systems Engineering, 6th Edition, John Wiley & Sons, USA, 2011.

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Katsuhiko Ogata, Modern Control Engineering (5th Edition), Pearson Education International, Inc., 2010.

Richard C. Dorf and Robert H. Bishop, Modern Control Systems (12th Edition), Pearson Educational International, 2011.

Rao V. Dukkipati, Analysis and Design of Control systems Using MATLAB, Published by New Age International (P) Ltd., Publishers, 2006

Benjamin C. Kuo, Automatic Control Systems (7th Edition), Prentice-Hall International, Inc., 1995.

Katsuhiko Ogata, MATLAB For Control Engineers, Pearson Education International, Inc., 2008.


Assessment

TEST 1

Topic 1 & 2

15 October 2014

15%

TEST 2

Topic 3 & 4a

26 November 2014

15%

FINAL EXAMINATION

28 Dec 17 Jan 2015

50%

Assignment

20%

CHAPTER 1 Introduction to system

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SKEE 3133

CONTROL:SYSTEM MODELING &

SIMULATION

SKEE 3133SYSTEM MODELING

AND ANALYSIS


Content

Control System Basics1.11.1

History of Control System 1.21.2

Control System Configuration 1.31.3

Examples of Control Systems1.41.4

Analysis and Design Objectives1.51.5

Simulation Software in Control MATLAB 1.61.6

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1.1CONTROL SYSTEMS BASICS

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INTRODUCTION

What do these two have in common? Highly complicated dynamics! Both are capable of transporting

good and people over long distances.

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BUT One is controlled, and the

other is not!

Control is the hidden technology that you meet everyday.


Introduction Control systems are important

and present almost everywhere in our daily lives.

Examples of control systems: washing machine, radio antenna, rockets/missiles, robots, room air condition.

God created control systems. Examples..

anyone.?

PTP, Malaysia


CONTROL SYSTEMS

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A control system provides an output or response for a given input or stimulus.

A Controlled Variable determines the input and output of a control system.

Example: Elevator buttons and the desired level (Input), actual level of elevator (Output), elevator level -> controlled variable.


Control System Basics- General Control System Block Diagram

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Outputsignal

(actualresponse)

Controller Plant

Subsystem 1

Subsystem 2

Process

ValveMotor

CONTROL SYSTEM

Input signal

(desired output/ setpoint)

Actuator


Position control Robot arm, crane systems, elevator, satellite tracking

Speed control Speed of airplane, washing machine, climbing robot

Temperature controlAir condition, heater, furnace

Level control Level of liquid, water.

Vibration control Machine vibration, Car suspension

CONTROL SYSTEM: Examples


Advantages of Control SystemsFor power amplification

e.g. To move containers at a port

For remote control

e.g. in controlling the movements of robots working in contaminated areas where human presence should be avoided

For convenience of input form

e.g. in a temperature control system, the turn of a knob corresponds to certain desired room temperature.

For compensation for disturbance

e.g. to maintain antenna position in the presence of strong wind.

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1.2HISTORY OF CONTROL

SYSTEMS

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History of Control System

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Early Simple

20th Century Extensive use of

sensors

Contemporary Widespread

applications

1900s 2000s

Al Jazari Water clock (1206)

Steam pressure & temperature control systems (1680s)

Speed control (1745) Stability Theories

Routh-Hurwitz (1877)

Lyapunov (1892)

Automatic Ship Steering (1922)

PID Controller (1920s) Feedback Control System

Technique (1930s) Root locus, Bode, Nyquist

(1948)

Navigation Entertainment Smart Homes Military Space Application Chemical Process Nanosystems


al Jazari Elephant Clock

800 years ago Al-Jazari has invented a sophisticated and automatic clock to track a time using water technology.

An example of the Muslim origins of modern automation and robotics.

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al Jazari Elephant Clock

Al-Jazari (1136-1206) was highly

creative and innovative engineer

His crowning achievement was converting rotational motion to linear a crucial to pumps, engines and many other machines.

He is known as a Father of Robotics

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History 20th Century Applications

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Contemporary Applications

22 CHAPTER 1 Intro to Control Systems (Dr Hazlina Selamat)


Manual Control

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Human-aided control

Operator constantly observe the deviation and make corrections when necessary

Not consistent

Hundreds of variables to be controlled

liquid flow in

liquid flow out

liquid

tank

valve


Automatic Control

To replace humans with machines (nowadays, computers) to implement the control of the plant.

Measurement sensors/transducers

Decision computers

Control action actuators

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1.3CONTROL SYSTEM

CONFIGURATION Open-Loop & Closed-Loop Systems

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Control System Configuration

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Open-loop Closed-loop


Open-loop Control SystemThe output signal of an OLCS is not fed back to influence the control action.

With disturbance/noise, the desired response cannot be achieved, actual desired response/output.

Example:

Systems that work based on time are OLCS.

The result may not be accurate.

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Closed-Loop Control Systems

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The output signal of a CLCS is fed back to influence the control action and improve overall system performance.

The difference (actual and desired response) will be used to determine the control action


Closed-loop Control System

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OutputInput transducer Plant

Input ++

Disturbance

+

-

Controller

Output transducer

Process variable(PV)

Controlled variable(CV)

output of the plant to be controlled

Manipulated variable(MV)

input variable into the plant so that the plant output achieves the SP value

Setpoint(SP)

desired output to be achieved


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Feedback control systems are often referred to as CLCS

Input transducer converts the form of the input to the form used by the controller

An output transducer measures the output response and converts it into the form used by the controller (from physical parameters to electrical signals

The first summing junction algebraically adds the signal from the I/P to the signal from the O/P, which arrives via the feedback path.

Closed-loop Control System


The o/p signal is substracted from the i/p signal. The result is generally call the actuating signal (the actuating signals value is equal to the actual difference between the I/P and the O/P), the actuating signal is called the error.

The CLCS compensates for disturbances by measuring the o/p response, feeding that measurement back through a feedback path, and comparing that response to the I/P:

If there is a difference between the two responses, the systems drives the plant, via the actuating signal, to make a correction.

If there is no difference, the system does not drive the plant, since the plants response is already the desired response

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Example: Liquid Level Control System

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liquid flow in

liquid flow out

liquid

tank

valve

Controller

Liquid level plant

Level Setpoint

++

Level sensor

Setpoint voltage, VSP

Input transducer Pump

Pump voltage, Vpump

Input flowrate, Qin

Output level voltage, Vlevel

Liquid level, H

Measurement noise

SP

PV

MV CVActuator Plant

o/p transducer


OLCS & CLCS

OLCS CLCS

Structure simple complicated

Sensitivity to parameter variations

sensitive less sensitive

Disturbance cannot handle can handle

Applications limited various systems

Cost cheap expensive


1.4EXAMPLES OF CONTROL

SYSTEMS

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Examples

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Power amplification in a dish-type antennas

Varying in diameter from 8 to 30 metres

Serving an Earth station in a satellite communications network.

Remote control robots in contaminated area: Sojourner

Roving on Mars in 1997. Solar-powered, 11.5 kg. Speed: 0.4 meters/minute Its wheel system enabled it to climb over

obstacles one-and-a-half wheel diameters tall.


Examples

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Convenient input for a thermostat

Position to heat Disturbance compensation in a Rolling Mill

Maintain steel thickness despite variations/disturbance

CHAPTER 0 Course Introduction (Dr Hazlina Selamat)


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Other Example: High-speed Train Suspension System


1.5ANALYSIS AND DESIGN

OBJECTIVES

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Tran

sien

t Res

pons

e Transient response is the case when the plant is changing from one steady state to another, when there are changes in the input signal

Stab

ility A system that can

produce a consistent/steady output is a stable system. An unstable system is harmful to the plant and may cause serious accidents

Stea

dy-s

tate

res

pons

e Steady state response only exists for stable systems. An important characteristic for design is the steady state error

Specifications of Control SystemsControl systems are dynamic: it responds to the input by going through a transient phase before settling to the steady state phase.


Specifications of Control Systems


Satisfactory transient response Rise time, settling time, overshoot1

Stable system2

Zero steady-state error3

Objectives


Example: Elevator

Objectives Solution?


1.5CONTROL SYSTEM DESIGN

PROCESS

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Classifications of control systems

Type of Signal

Continuous control system

Discrete control system

Mathematical model

Mathematical model

Linear control system

Non-linear control system

Control Objectives

Control Objectives

Kinatic(tracking) control system

Process (regulating) control system

Based on the purpose of the system and the relevant classes it belongs to


Controller Design Process- General

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Design of controllerController structure Controller type

AnalysisTime domain Frequency domain

Mathematical modellingLaws of Physics System identification


Controller Design Process- General

STEP 1 Transform

requirements into physical systems

STEP 2 Draw a

functional block diagram

STEP 3 Create a

schematic

STEP 4 Develop

mathematical model (block diagram)

STEP 5 Reduce

block diagram

STEP 6 Analyze &

Design

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Chapter 1 Chapter 2 Chapter 3 Chapter 4


Schematic

Draw a functional block diagram

Determine a physical system

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Example Antenna Position Control

- requirements- overall concept

- components- hardware

- assumptions- simplifications


Block diagram

Analysis

Reduced block diagram

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Mathematical model


1.6MATLAB

MATLAB Control System Toolbox

Simulink

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Computer Aided Control System Design (CACSD)

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MATLAB

Important tool in control system design.

Recall: To achieve: PO4: Ability to work with

modern instrumentation, software and hardware.

through: CO4: Apply MATLAB software

in analyzing control system performance

MATLAB contains: Lots of Toolboxes one

of them is Control System Toolbox

Simulink click and drag

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Control System Toolbox

Contains a set of functions relation to control system design.

Can be used together with other MATLAB functions or functions from other toolboxes.

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Simulink More graphical. Code writing is minimal.

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Review Questions Name 3 applications of feedback control system. Give 3 examples of open-loop systems. Give an example of what happen to a system that

is unstable.

Name 3 approaches to the mathematical modeling of control systems.

How do we classify control systems? What are the steps involved in designing a control

system?

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Problem

A temperature control system operates by sensing the difference between the thermostat setting and the actual temperature and then opening a fuel valve an amount proportional to this difference. Draw a functional closed-loop block diagram, identifying the input and output transducers, the controller and the plant. Further, identify the input and output signals of all subsystems previously described.

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END OF CHAPTER 1

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SKEE 3133 Chapter 1 Revised