UNIVERSITI PUTRA MALAYSIA POSITION …psasir.upm.edu.my/12204/1/FK_2003_45_A.pdf · Kajian...

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UNIVERSITI PUTRA MALAYSIA POSITION CONTROL STRATEGIES OF DC SERVO MOTOR ERNY AZNIDA ALWI FK 2003 45

Transcript of UNIVERSITI PUTRA MALAYSIA POSITION …psasir.upm.edu.my/12204/1/FK_2003_45_A.pdf · Kajian...

  

UNIVERSITI PUTRA MALAYSIA

POSITION CONTROL STRATEGIES OF DC SERVO MOTOR

ERNY AZNIDA ALWI

FK 2003 45

POSITION CONTROL STRATEGIES OF DC SERVO MOTOR

By

ERNY AZNIDA ALWI

Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in Fulfilment of the Requirements for the Degree of Master of Science

June 2003

DEDICATION

To MY BeLoVeD FaMiLY, HuBBY aND auNY

ii

Abstract of thesis presented to the Senate ofUniversiti Putra Malaysia in fulfilment of the requirements for the degree of Master of Science

POSITION CONTROL STRATEGIES OF DC SERVO MOTOR

By

ERNY AZNIDA ALWI

June 2003

Chairman: Samsul Bahari Mohd Noor, Ph.D.

Faculty: Engineering

Direct Current (DC) servo motor is mainly studied for its speed and position control.

This study however, concentrated only on the position control part. The technology of

position control of DC servo motor has evolved considerably over the past few years.

To date, various types of DC servo motor position control scheme have been developed.

To name some, there are microcontroller�based control, PC based control, adaptive

control and optimal control.

In this study, a simulation and a real time implementation of DC servo motor position

control are presented. The types of controller designed and tested are the proportional

integral derivative (PID) controller and the adaptive controller. PID control scheme is

chosen mainly because of its simplicity advantage while the adaptive scheme is chosen

due to its ability to adapt.

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With some modification and adaptation, these two designed schemes have been

interfaced via MA TLAB Real Time Toolbox to a servo trainer as the plant for real time

implementation. This toolbox contains a library of blocks with real time input and

output support. Following the design part, the modeling and simulation part are done.

The mathematical design or model of the controller then has been simulated in

MATLAB before being interfaced to the real plant. The PID and adaptive controller

have been successfully implemented to the plant with satisfactory results. Analysis has

been done to compare the performance of the two controllers from the simulation and

real time results.

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PERPUSTAKAAt>J SULTAN ABDUL SAMAD UNIVERSfTl PUmA MAlAYSIA

Abstrak tesis yang dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi keperluan untuk Ijazah Master Sains

STRA TEGI KA WALAN KEDUDUKAN MOTOR SERVO ARUS TERUS

Oleh

ERNY AZNIDA ALWI

Jun 2003

Pengerusi: Samsul Bahari Mohd Noor, Ph.D.

Fakulti: Kejuruteraan

Kajian berkenaan motor servo arus terns (DC) kebiasaannya tertumpu kepada kawalan

kelajuan dan kedudukannya. Walaubagaimanapun, dalam kajian ini, hanya kawalan

kedudukan sahaja akan diberi tumpuan. Teknologi kawalan kedudukan motor arus terus

telah berkembang pesat sejak beberapa tahun kebelakangan ini. Sehingga ke hari ini,

pelbagai jenis sistem kawalan kedudukan motor arus terns telah dibangunkan. Di

antaranya, kawalan berasaskan pengawal mikro, kawalan berasaskan komputer,

kawalan adaptasi dan kawalan optimal.

Dalam kajian ini, simulasi dan implementasi masa nyata dibentangkan. Jenis pengawal

yang direkabentuk dan diuji adalah pengawal terbitan kamiran perkadaran (PID) dan

pengawal adaptasi. Skima pengawal PID dipilih disebabkan kelebihannya yang mudah

manakala pengawal adaptasi dipilih kerana kebolehannya untuk menyesuaikan diri.

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Dengan sedikit pengubahsuaian dan penyesualan, kedua-dua sistem yang telah

direkabentuk disambungkan ke servo trainer yang merupakan loji untuk implementasi

masa nyata melalui antaramuka MA TLAB Real Time Toolbox. Perisian ini mengandungi

himpunan blok-blok dengan masukan dan keluaran masa sebenar. Selepas rekabentuk,

permodelan dan simulasi dilakukan. Rekabentuk matematik atau model pengawal

kemudiannya disimulasikan di dalam MATLAB sebelum diantaramukakan dengan loji

sebenar. Pengawal PID dan adaptasi telah berjaya diimplementasikan ke loji dengan

keputusan yang memuaskan. Analisa ke atas keputusan simulasi dan masa nyata

dijalankan untuk membandingkan prestasi kedua-dua pengawal.

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ACKNOWLEDGEMENTS

I would like to express my appreciation especially to my project supervisor, Dr. Samsul

Bahari Mohd Noor and all the supervisory committee for the given guidance and time

spent. Many thanks also go to my loving family, my parents, husband and my beautiful

daughter for their unconditional support and love which without it this work would not

have been possible. Finally special thanks to my friends and all who have contributed in

making my research a success.

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I certify that an Examination Committee met on 4th June 2003 to conduct the final examination of Emy Aznida Alwi on her Master of Science thesis entitled "Position Control Strategies of DC Servo Motor" in accordance with Universiti Pertanian Malaysia (Higher Degree) Act 1 980 and Universiti Pertanian Malaysia (Higher Degree) Regulation 1 98 1. The Committee recommends that the candidate be awarded the relevant degree. Members of the Examination Committee are as follows:

Syed Javaid Iqbal, Ph.D. Lecturer Faculty of Engineering

Universiti Putra Malaysia (Chairman)

Samsul Bahari Mohd Noor, Ph.D. Lecturer Faculty of Engineering

Universiti Putra Malaysia (Member)

Sen an Mahmood, Ph.D Lecturer Faculty of Engineering Universiti Putra Malaysia (Member)

Jasronita Jasni Lecturer Faculty of Engineering

Universiti Putra Malaysia (Member)

GULAM HMAT ALI, Ph.D. ProfessorlDeputy Dean School of Graduate Studies

Universiti Putra Malaysia

Date: 0 4 DEC 2fXB

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This thesis submitted to the Senate of Universiti Putra Malaysia and has been accepted as fulfilment of the requirements for the degree of Master of Science. The members of the Supervisory Committee are as follows:

Samsul Bahari Mohd Noor, Ph.D. Lecturer Faculty of Engineering Universiti Putra Malaysia (Chairman)

Senan Mahmood, Ph.D Lecturer Faculty of Engineering Universiti Putra Malaysia (Member)

Jasronita Jasni Lecturer Faculty of Engineering Universiti Putra Malaysia (Member)

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AINI IDERIS, Ph.D. ProfessorlDean School of Graduate Studies Universiti Putra Malaysia

DECLARATION

I hereby declare that the thesis is based on my original work except for quotations and citations which have been duly acknowledged. I also declare that it has not been previously or concurrently submitted for any other degree at UPM or other institutions.

x

ERNY AZNIDA AL WI

Date: %t2-�S &')

TABLE OF CONTENTS

DEDICATION ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL DECLARATION LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS

CHAPTER

1

2

INTRODUCTION 1 . 1 Importance of Servo Position Control 1 .2 Objectives 1 .3 Thesis Organization

LITERATURE REVIEW 2.1 Introduction 2.2 Position Controller Development for Different Types

of Motor 2.2. 1 The Optimal Position Controller 2 .2.2 The Robust Position Controller

2.3 The PID Controller 2.3 . 1 Tuning the PID Controller

2.4 Adaptive Control Scheme 2.4.1 Gain Scheduling 2.4.2 Model Reference Adaptive Systems 2.4.3 Self-Tuning Regulators 2.4.4 Dual Control

2.5 Recursive Least Square Estimator 2.6 System Representation 2.7 System Stability 2.8 Servo Motor

2.8. 1 Definition of Servo System 2.8.2 Types of Motor 2.8.3 Motor Amplifier Dead-zone

2.9 Summary

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Page

ii 1ll V Vll viii x xiii XIV XVll

1 1 2 3

4 4

5 6 7 8 10 12 13 14 15 16 16 1 7 1 9 1 9 20 21 21 22

3 METHODOLOGY 23 3 . 1 Introduction 23 3 .2 Description of Servo System 24 3 .3 Method of System Representation 25 3.4 Determination of Servo System Model 26

3.4.1 Actuator and Sensor Characteristics 27 3.4.2 Motor and Sensor Characteristics 29 3.4.3 Measurement of kj• km and ke 29

3 .5 Constructing the SIMULINK Model 35 3.5 . 1 Designing Model o f Servo System with

Controllers 35 3.5 .2 Designing Model of Controller with Real

Time Feature 41 3 .6 Hardware Configuration 42 3 .7 Summary 44

4 RESULTS AND DISCUSSION 45 4. 1 Introduction 45 4.2 Experimental Results 46 4.3 Mathematical Solution of System Model 49 4.4 SIMULINK Model Designs 52

4.4. 1 Model of Servo System with Controller 52 4.4.2 Model of Controllers for Real Time

Implementation 53 4.5 SIMULINK Simulation Results 54 4.6 Real Time Implementation Results 64 4.7 Discussion 72

5 CONCLUSION AND FUTURE WORKS 74 5.1 Conclusion 74 5 .2 Future Works 76

REFERENCES 77 APPENDICES

A Experimental Data 8 1 B SIMULINK S-Function Files 84 C Matlab M-Files for SIMULINK Model 87 D Data Sheets 127

BIODATA OF THE AUTHOR 1 30

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Table 4. 1 : Data of Experiment 1

Table 4.2 : Data of Experiment 2

Table 4.3 : Data of Experiment 3

LIST OF TABLES

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Page

81

82

83

LIST OF FIGURES

Page

Figure 2. 1 : A servo system 20

Figure 3 . 1 : The servo trainer 24

Figure 3 .2 : Servo control system: clutch engaged 26

Figure 3 .3 : Block diagram representation of servo control system 27

Figure 3 .4 : Block diagram of overall transfer function for servo control 29 system

Figure 3 .5 : Connection for Experiment 1 , to determine the value of motor 32 gain constant, k;

Figure 3 .6 : Connection for Experiment 2, to determine the value of velocity 33 sensor gain constant, kw

Figure 3 .7 : Connection for Experiment 3, to determine the value of angle 34

sensor gain constant, ko

Figure 3 .8 : Opening a new model window 36

Figure 3 .9 : SIMULINK Library Browser and a blank model window 37

Figure 3 . 1 0 : Using the SIMULINK Library Browser 37

Figure 3 . 1 1 : Example of a complete model 39

Figure 3 . 1 2: To reveal the masked block 39

Figure 3 . 1 3 : Underneath the masked PID block 40

Figure 3 . 1 4 : Setting the parameter value 40

Figure 3 . 1 5 : Selecting the hardware driver 43

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Figure 3 . 1 6 : Hardware driver parameter setting

Figure 4. 1 : Result of Experiment 1 , to determine the value of k{

Figure 4.2 : Result of Experiment 2, to determine the value of km

Figure 4.3 : Result of Experiment 3, to determine the value of k{)

Figure 4.4 : PID controller

Figure 4.5 : Adaptive controller

Figure 4.6 : Real time PID controller

Figure 4.7 : Real time adaptive controller

Figure 4.8 : Output ofPID controller

Figure 4.9 : Output of adaptive controller

Figure 4. 10 : Control signal for adaptive controller

Figure 4. 1 1 : Control signal for PID controller

Figure 4. 12 : Square wave output for adaptive controller

Figure 4. 1 3 : Sawtooth output for adaptive controller

Figure 4. 1 4 : Square wave output for PID controller

Figure 4. 1 5 : Sawtooth output for PID controller

Figure 4. 16 : Input signal of square wave input Vs the output for adaptive controller

Figure 4. 17 : Input signal of sawtooth input V s the output for adaptive controller

Figure 4. 1 8 : Control signal for square input of the adaptive controller

Figure 4. 1 9 : Control signal for sawtooth input of the adaptive controller

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6 1

6 1

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Figure 4.20 : Output of P ID controller for square input

Figure 4.2 1 : Output of P ID controller for sawtooth input

Figure 4.22 : Control signal of P ID controller for sawtooth input

Figure 4.23 : Control signal of P ID controller for square input

Figure 4 .24 : Real time output for PID controller

Figure 4.25 : Real time output for adaptive controller

Figure 4.26 : Real time control signal for PID controller

Figure 4 .27 : Real time control signal for adaptive controller

Figure 4.28 : Step input Vs real time output for PID controller

Figure 4.29 : Step input Vs real time output for adaptive controller

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7 1

LIST OF ABBREVIATIONS

e(t) Parameter estimates

A Forgetting factor

e Output shaft position (0)

OJ Shaft velocity / speed (rpm)

cp State vector

crt) Prediction error

b Friction coefficient of rotating component

DC Direct current

hp Horse power

ko Angle sensor gain (volts/rev)

kw Velocity sensor gain (volt.sec/rev)

K(t) Weighting factor vector

Kd Derivative gain

K, Integral gain

ki Motor sensor gain (rev/sec. volt)

k{, kt' Gain constant of load

km,km' Motor constant

Kp Proportional gain

LQ Linear quadratic

L Motor armature inductance (H)

pet) Covariance matrix

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PI Proportional-integral

PID Proportional-integral-derivative

R Motor armature resistance (0 )

rev Revolution

RLS Recursive least square

rpm Rotation per minute

T Time constant (sec)

v Input drive voltage (volts)

v Motor drive amplifier voltage (volts)

VI Load control voltage (volts)

VSC Variable structure control

Yo Position output (volts)

Yro Velocity output (volts)

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CHAPTER 1

INTRODUCTION

1.1 Importance of Servo Position Control

The rapid development of electronics world has not left the area of motor control

deserted. The initiation of motors has brought about profound changes in everyday life

for over a century. At present, there are numerous system topologies for motor control

depending on the motor type and application as to be discussed in the following chapter.

Servo motors have replaced traditional gears, belts, and pulleys, thereby eliminating the

wear and failure problems associated with the use of these older technologies. These

servo motors are used in applications that require position and speed or torque control,

and these range from robotics and semiconductor equipment to packaging, food and

beverage, and printing. Use of servo motors in factory machines and equipment are

helping to improve productivity in a wide array of processes.

DC motor systems are also used widely in various fields of technology. They are used

in power plants to generate electrical power and in industrial occupancies to furnish the

required mechanical motive power to drive mechanical machinery and control various

industrial processes. Ranging from robotics manipulators to the disk drive of a

computer, DC motor acts as one of the vital part. For both applications, the position

control of the motor is the major part to be given attention. Efforts made on controlling

the position of DC motor result in so many types of control scheme for the mentioned

purpose. For instance, there are micro controller-based control, PC based control,

adaptive control, optimal control, etc. Some of these control schemes will be explained

and discussed briefly in this study. More detailed discussions will be centered upon the

studied controllers, which are the PID and adaptive controllers.

1.2 Objectives

The main intention of this project is to implement the designed position control

strategies of DC servo to the real plant, via newly introduced real time software, the

MATLAB Real Time Toolbox. Among other objectives to be achieved through out the

study are:

(i) To describe in detail how to develop the plant model, plus description

on how to design the two types of controller, the PID and the adaptive

controller by means of SIMULINK and by making use of MATLAB

Real Time Toolbox.

(ii) To apply the developed or established control strategies to real DC servo

motor based on simulation done in SIMULINK, MATLAB.

(iii) To analyze the stability and to compare the simulation performance of

the two designed controllers of DC servo position.

(iv) To analyze the stability of adaptive control system, plus to compare the

performance between adaptive controller and conventional PID

controller in real time implementation.

2

1.3 Thesis Organization

This thesis describes the development of real time implementation of DC servo position

control schemes. The first chapter introduces the background and the aim of this study.

Subsequently, the second chapter reviews the present and past works on various means

of position control of a DC motor. Previous research examples on related topic will be

unleashed. It also includes brief descriptions of methods to be used in this study. The

third chapter discusses the way and the flow of works towards realizing the project

designs and simulations. Detailed explanation on designing the controller via

SIMULINK also presented in this chapter. This includes the hardware configurations

and software designs. The fourth chapter reveals the simulations and experimentations

results obtained. Analysis and discussions upon the achieved results are featured in this

chapter. Finally, the last chapter concludes the study with a few suggestions of future

works, to further develop the design.

3

2.1 Introduction

CHAPTER 2

LITERATURE REVIEW

Various importance of position control in the industry and research fields has been

explained in the first paragraph of the previous chapter. It is imperative for the user to

understand the performance specification of different motor types when designing a

product for position control. For position control systems, three major motor types are

most commonly used: stepper motors; DC servo motors, in which the current�carrying

windings move and the second field is stationary and usually comes from a permanent

magnet; and brushless DC motors with a moving permanent magnet and stationary

current-carrying windings [30] .

Most motion control systems today make use of either stepper or DC servo motors.

Both motor types offer precise positioning and speed control but they differ in a number

of ways [30] . For DC motors, stator field is produced by either a field winding or by

permanent magnets while rotor field is set up by passing current through a commutator

and into the rotor assembly. Their rotational speed is dependant on the strength of the

rotor field.

4

Whereas, the stepper motors are electromechanical actuators which convert digital

inputs to analog motion. They are particularly well suited to applications where the

controller signals appear as pulse train. Also, they are limited to about one horsepower

and 2000 rpm, therefore limiting them in many applications [ 1 ] . Due to these reasons,

the DC motor is found more suitable and has been chosen for this study.

To date, lots of other controller types [2,4,6] have been implemented for the same

purpose, position control of motors. However this study differs in a way that it is

realized using the Real Time Toolbox, which is a new tool applied for position control

of DC servo. A couple of previous designs of various controllers for motor position

control purpose will be featured further in section 2.2 of this chapter.

2.2 Position Controller Development for Different Types of Motor

Researchers designed different types of controllers to suit different types of motors.

Despite the latest emphasis of the ever-evolving fuzzy logic control technology, the

conventional controllers are not lagging in terms of efficiency and simplicity

advantages. Many engineering problems demand automatic control in the presence of

uncertainties and unforeseen large changes in system parameters and input signal. To

obtain robustness to uncertainties, a lot of adaptive control approaches have been

proposed in recent years. A few approaches of position control techniques done in

previous researches [2,3,5] will be presented briefly in this section.

5

2.2.1 The Optimal Position Controller

Even though the designed techniques for the sliding mode are well established [8], it is

not easy to shape the dynamics of the reaching phase. Some process may require an

optimal performance. Hence to comply with this reason to be considered, the linear

quadratic (LQ) method is an easy way to design the control law. This proposed method

has the fully flexibility of shaping the dynamics of the closed loop system to meet the

desired specification. An optimal controller has been designed via combining the

classical state feedback control and variable structure control (VSC) and demonstrated

on a synchronous reluctance motor to meet this purpose [2]. This new method fully

matches the merits of the easy design of the linear quadratic method and the strong

robustness of the variable structure control. This method has proven that the

synchronous reluctance motor can be used in position control and the designed

performance can be easily obtained regardless of the disturbance and uncertainty.

While Morris, et. al. [3] has addressed the problem of controlling a two flexible link

manipulator system, and proposed a quadratic optimal control and a computed-torque

controller as the solutions. The study initially explained the necessity for having an

accurate static and dynamic model of the two flexible link manipulator, which properly

represents the coupling and interaction between links . The functions to be fulfilled by

the controller of a flexible manipulator system were to compensate for the static

deflection of the flexible links under gravity forces and also to reduce both the

magnitUde and the time duration of link oscillations, which arise naturally out of its

6