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

Transcription

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

2 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

3 DEDICATION To MY BeLoVeD FaMiLY, HuBBY and auny ii

4 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: Faculty: Samsul Bahari Mohd Noor, Ph.D. 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. iii

5 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. iv

6 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: Fakulti: Samsul Bahari Mohd Noor, Ph.D. 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. v

7 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. vi

8 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. vii

9 I certify that an Examination Committee met on 4 th 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 1980 and Universiti Pertanian Malaysia (Higher Degree) Regulation 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 viii

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

11 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. ERNY AZNIDA AL WI Date: %t2- S &') x

12 TABLE OF CONTENTS Page DEDICATION ABSTRACT ABSTRAK ACKNOWLEDGEMENTS APPROVAL DECLARATION LIST OF TABLES LIST OF FIGURES LIST OF ABBREVIATIONS ii 1ll V Vll viii x xiii XIV XVll 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 The Optimal Position Controller The Robust Position Controller 2.3 The PID Controller Tuning the PID Controller 2.4 Adaptive Control Scheme Gain Scheduling Model Reference Adaptive Systems Self-Tuning Regulators Dual Control 2.5 Recursive Least Square Estimator 2.6 System Representation 2.7 System Stability 2.8 Servo Motor Definition of Servo System Types of Motor Motor Amplifier Dead-zone 2.9 Summary xi

13 3 METHODOLOGY 3.1 Introduction 3.2 Description of Servo System Method of System Representation Determination of Servo System Model Actuator and Sensor Characteristics Motor and Sensor Characteristics Measurement of kj km and ke Constructing the SIMULINK Model Designing Model of Servo System with Controllers Designing Model of Controller with Real Time Feature Hardware Configuration Summary 44 4 RESULTS AND DISCUSSION Introduction Experimental Results 46 Mathematical Solution of System Model SIMULINK Model Designs Model of Servo System with Controller Model of Controllers for Real Time Implementation SIMULINK Simulation Results Real Time Implementation Results Discussion CONCLUSION AND FUTURE WORKS Conclusion Future Works REFERENCES 77 APPENDICES A Experimental Data 81 B SIMULINK S-Function Files 84 C Matlab M-Files for SIMULINK Model 87 D Data Sheets 127 BIODATA OF THE AUTHOR xii

14 LIST OF TABLES Page Table 4.1 : Data of Experiment 1 Table 4.2 : Data of Experiment 2 Table 4.3 : Data of Experiment xiii

15 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 3.10 : Using the SIMULINK Library Browser 37 Figure 3.11 : Example of a complete model 39 Figure 3.12: To reveal the masked block 39 Figure 3.13 : Underneath the masked PID block 40 Figure 3.14 : Setting the parameter value 40 Figure 3.15 : Selecting the hardware driver 43 xiv

16 Figure 3.16 : Hardware driver parameter setting 43 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 4.11 : Control signal for PID controller Figure 4.12 : Square wave output for adaptive controller Figure 4.13 : Sawtooth output for adaptive controller Figure 4.14 : Square wave output for PID controller Figure 4.15 : Sawtooth output for PID controller Figure : 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 4.18 : Control signal for square input of the adaptive controller Figure : Control signal for sawtooth input of the adaptive controller xv

17 Figure 4.20 : Output of PID controller for square input Figure 4.21 : Output of PID controller for sawtooth input Figure 4.22 : Control signal of PID controller for sawtooth input Figure 4.23 : Control signal of PID 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 xvi

18 LIST OF ABBREVIATIONS e(t) A Parameter estimates Forgetting factor e Output shaft position (0) OJ Shaft velocity / speed (rpm) cp crt) b DC hp ko kw K(t) Kd State vector Prediction error Friction coefficient of rotating component Direct current Horse power Angle sensor gain (volts/rev) Velocity sensor gain (volt.sec/rev) Weighting factor vector Derivative gain K, Integral gain ki k{, kt' km,km' Kp LQ L pet) Motor sensor gain (rev/sec. volt) Gain constant of load Motor constant Proportional gain Linear quadratic Motor armature inductance (H) Covariance matrix xvii

19 PI PID Proportional-integral Proportional-integral-derivative R Motor armature resistance (0 ) rev RLS rpm T v v VI VSC Yo Yro Revolution Recursive least square Rotation per minute Time constant (sec) Input drive voltage (volts) Motor drive amplifier voltage (volts) Load control voltage (volts) Variable structure control Position output (volts) Velocity output (volts) xviii

20 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

21 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

22 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

23 CHAPTER 2 LITERATURE REVIEW 2.1 Introduction 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

24 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

25 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 fu lly 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