Development Of Data Acquisition System For Tyre Force Measuring Device.
VERIFICATION
“I hereby declare that I have read through this thesis and found that it has complied the partial fulfillment in awarding the Bachelor Degree of Mechanical Engineering
(Automotive)”
Signature : ……….
Supervisor’s Name : ………..
Date : ………..
EN. MOCHAMAD SAFARUDIN
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DEVELOPMENT OF DATA ACQUISITION SYSTEM FOR TYRE FORCE MEASURING DEVICE
LEE TZE JIAN
This Report is Submitted in Partial Fulfillment of Requirements for the Bachelor Degree of Mechanical Engineering (Automotive)
Faculty of Mechanical Engineering Universiti Teknikal Malaysia Melaka
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DECLARATION
“I hereby declare that this project report entitled
DEVELOPMENT OF DATA ACQUISITION SYSTEM FOR TYRE FORCE MEASURING DEVICE
is written solely by me and with great effort and that none of the parts have been plagiarized without citations.”
Signature : ……….
Author’s Name : ………..
Date : ………..
LEE TZE JIAN
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DEDICATION
Dedicated to my beloved Family, Father (Mr. Lee Kwong Leong), Mother (Ms. Chai Siew May), Siblings (Mr. Lee Tze San & Ms. Lee Joe Ee), and not forgetting my dearest and closest fellow friends who have given me endless support and the greatest will to complete this project.
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ACKNOWLEDGEMENT
From deep within my heart, I would like to portray my unbounded thanks for all the support, encouragements and inspirations I have received throughout the duration of this project.
My greatest gratitude to my supervising lecturer, Mr. Mochamad Safarudin, whom I had a pleasurable and yet conducive cooperating relationship. He has given me tremendous guidance and advice whenever I fell short. He gave me a pat in the back and harsh encouragements for me to go through the hard times. And he is truly a remarkable person.
I would also like to convey my thanks and appreciation to the FKM staff and personnel who have given me much help despite the trouble caused. The technicians who assisted me in the lab without hoping for rewards and the co-curricular department officer who has gone through a lot of trouble in aiding my project.
Deepest heartfelt for my family who has been supporting me from hundreds of miles away. They had always cared and worried about my well being.
The list goes on and to keep it short, lastly, I would like to thank everyone who has facilitated and helped me even the slightest in completing this project. To those whom I did not specifically mention, you have my gratitude for moving me closer to my goal.
Thank You.
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ABSTRAK
Kajian ini menjelaskan tentang pembinaan sistem perolehan data untuk alat pengukuran daya tayar. Alat pengukuran daya tayar ini memerlukan dua belas tolok ketegangan di mana kesemua tolok-tolok ini adalah tolok aktif yang membolehkan penghasilan data daya dan daya tuas yang tertentu. ‘Wheatstone Half Bridge’ diaplikasikan pada setiap tolok ketegangank. Setiap daya dan daya tuas ditugaskan kepada dua tolok ketegangan di mana satu tolok akan mengalami keregangan manakala yang satu lagi akan mengalami tekanan. Penguat isyarat dan penapis isyarat tidak ditambah kedalam litar kerana sistem perolehan data mampu mengesan data daripada alat pengukuran daya tayar dan juga alat ini digunakan dalam aplikasi automotif di mana daya-daya yang dijangkakan adalah besar. Sebarang gangguan yang kecil boleh diabaikan Sebuah sistem perantaraan pengguna bergrafik dibina menggunakan MATLAB untuk membolehkan perhubungan antara pengguna dengan alat pengukuran daya tayar. Alat pengukuran daya tayar ini ditentu ukurkan melaui eksperimen. Sistem perantaraan pengguna bergrafik menghasilkan keputusan visual dari segi graf.
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ABSTRACT
In this study, a data acquisition system for the tire force measuring device is developed. The tire force measuring device requires twelve strain gauges which all of them act as active gauges that produces output for a specific force or moment component. Wheatstone Half Bridge is applied in determining the changes in the resistance of the strain gauges which is then converted into voltage changes. Each force or moment is assigned to two strain gauges which one of the strain gauge is assigned to compression while the other strain gauge is assigned to tension. Amplifier and filter are not needed as the data acquisition system managed to detect outputs from the device and the device is applied solely in automotive applications where forces and moments are expected to be large, rendering small noises negligible. A graphical user interface is programmed using MATLAB to bridge the link between the user and the tire force measuring device. The tire force measuring device is calibrated through experimental means. The graphical user interface provides the means of graphical output in terms of graphs.
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TABLE OF CONTENT
CHAPTER CONTENT PAGE
VERIFICATION
TITLE i
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENTS iv
ABSTRAK v
ABSTRACT vi
TABLE OF CONTENT vii
LIST OF TABLES xi
LIST OF FIGURES xii
LIST OF SYMBOLS xvi
LIST OF APPENDICES xviii
CHAPTER 1 INTRODUCTION 1
1.1 The Wheel Dynamic Test Rig 1 1.2 Design of the Six-Component Force
Sensor 2
1.3 User Interface 3
1.4 Problem Statement 4
1.5 Objectives of Study 5
1.6 Scope of Study 5
1.7 Significance of Study 6
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viii
CHAPTER CONTENT PAGE
CHAPTER 2 LITERATURE REVIEW 7
2.1 Data Acquisition and Data Acquisition
System 7
2.2 Strain, Stress and Poisson’s Ratio 11 2.3 Resistance-Type Strain Gauge 13 2.3.1 Principle of Strain Gauges 14 2.3.2 Types of Strain Gauges 14 2.3.3 Structure of Foil Strain
Gauge 15
2.4 Wheatstone Bridge 15
2.4.1 Quarter Bridge 17 2.4.2 Half Bridge and Full Bridge 18 2.4.3 Wheatstone Bridge Signal
Conditioning 19
2.4.4 Strain Gauge Signal
Conditioners 26
2.5 Effects of Lead Wires 27
2.6 Beam-Type Load Cell 32
2.7 Principle of Six-Axis Tire Force Measurement 35 2.8 Analytical and Experimental Method of
Calibration 38
2.9 Summary 39
CHAPTER 3 METHODOLOGY 40
3.1 Flow Chart of Methodology 41 3.2 Details of Methodology of the Study 42 3.2.1 Preliminary Stage 42 3.2.2 Research Stage 42 3.2.3 Instrumentation System Design 43 3.2.4 Theoretical Assessment 45
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CHAPTER CONTENT PAGE
3.2.5 Data Acquisition Coding in
MATLAB and GUI Design 47 3.2.6 Circuit Construction and Wiring 49
3.2.7 Test Run 53
3.2.8 Calibration 53
3.2.8.1 Calibration Theories 53 3.2.8.2 MATLAB Coding for
Calibration 57
3.3 Summary 59
CHAPTER 4 RESULTS AND DISCUSSION 61
4.1 The GUI of Tire Force Measuring Device 61 4.2 Calibration Results of Tire Force Measuring
Device 71
4.2.1 Calibration for longitudinal force,
71 4.2.2 Calibration for lateral force, 74 4.2.3 Calibration for vertical force, 77 4.2.4 Calibration for rolling moment, 80 4.2.5 Calibration for overturning
moment, 83
4.2.6 Calibration for self aligning
moment, 86
4.3 Finding the Strain in the Strain Gauges 88 4.4 Applying Results of Calibration 94 4.5 Limitations and Errors in Calibration 95
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x
CHAPTER CONTENT PAGE
CHAPTER 5 CONCLUSION 100
5.1 Conclusion 100
5.2 Recommendations 104
5.3 Future Research 105
REFERENCES 106
BIBLIOGRAPHY 107
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xi
LIST OF TABLES
NO. TITLE PAGE
2.1 Recommended Power Densities 21
2.2
Resistance (Ω per 100 ft or 30.5 m) of Solid
Conductor Copper Wire and Signal Loss Factor, L, for Gauges with = 120Ω
30
4.1 Table calibration of longitudinal force, . 70
4.2 Table calibration of lateral force, . 73
4.3 Table calibration of vertical force, . 76
4.4 Table calibration of rolling moment, . 79
4.5 Table calibration of overturning moment, . 82
4.6 Table calibration of self aligning moment, . 85
4.7 Simulation and experimental values of strain, , due
to 5000 N load 93
5.1 Equations of forces and moments from calibration. 101
5.2 Comparison between experimental and simulation
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xii
LIST OF FIGURES
NO. TITLE PAGE
1.1 Six-Component Force Sensor 2
2.1
USB Data Acquisition System, National Instruments, NI USB-6216, 16 inputs, 16 bit, 400kS/s, isolated multifunction I/O
10
2.2 Elongation and Contraction of Material When
Subjected to Tension and Compression 11
2.3 Structure of a Foil Strain Gauge 15
2.4 Configuration of Wheatstone Bridge Circuit 16
2.5 Configuration of Wheatstone Quarter Bridge Circuit 17
2.6 Configuration of Wheatstone Half Bridge Circuit 18
2.7 Configuration of Wheatstone Full Bridge Circuit 18
2.8 Four Common Strain Gauge Arrangements in a
Wheatstone Bridge 19
2.9
Allowable Bridge Voltage as a Function of Grid Area for Different Power Densities. (Courtesy of Micro-Measurements Division, Measurement Group, Inc., USA.)
23
2.10 Gauge Connections to Wheatstone Bridge. (a) Two
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xiii
NO. TITLE PAGE
2.11
Loss Factor, L, as a Function of Resistance Ratio
⁄ for Two and Three Lead Wire Systems 29 2.12
(a) Beam-Type Load Cells Incorporate an Elastic Element with Strain Gauges. (b) Gauge Position in the Wheatstone Bridge
33
2.13 Deformation due force in x-axis and z-axis 35
2.14 Deformation due to force in y-axis 35
2.15 Deformation due to moment in x-axis and z-axis 35
2.16 Deformation due to moment in y-axis 35
2.17 Forces and moments acting on the tire and tire
measuring device 36
3.1 Methodology flow chart 41
3.2 Configuration of strain gauges in a Wheatstone half
bridge 46
3.3 Placement of strain gauges and their numberings 50
3.4 Strain gauge attached to tire force measuring device 51
3.5 Wiring of tire force measuring device 51
3.6 Wheatstone half bridge circuits connected to the data
acquisition card via analog input with power supply 52
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xiv
NO. TITLE PAGE
3.8 Calibration for Fx, Fz, Mx and Mz 54
3.9 Calibration for Fy 55
3.10 Calibration for My 55
4.1 GUI menu for the tire force measuring device 60
4.2 The waiting bar of the graphical user interface menu
indicating experiment in progress 61
4.3 Generated graphs from the graphical user interface
program 61
4.4 Graph of voltage against load for Fx 70
4.5 Graph of load against voltage for Fx 71
4.6 Graph of voltage against load for Fy 73
4.7 Graph of load against voltage for Fy 74
4.8 Graph of voltage against load for Fz 76
4.9 Graph of load against voltage for Fz 77
4.10 Graph of voltage against load for Mx 79
4.11 Graph of load against voltage for Mx 80
4.12 Graph of voltage against load for My 82
4.13 Graph of load against voltage for My 83
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NO. TITLE PAGE
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xvi
LIST OF SYMBOLS
SYMBOL TITLE
A Area of grid of strain gauge
b Width of the cross section of the beam E Elastic modulus
Longitudinal Force Lateral Force Vertical Force
h Height of the cross section of the beam Electrical current in strain gauge L Original length
L Signal loss factor
ΔL Elongation
Bending moment Rolling Moment Pitching Moment Yawing Moment
P Load
Power density of strain gauge
Power that can be dissipated by the strain gauge R Original resistance
ΔR Change in resistance Resistance in strain gauge Resistance of a single lead wire
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xvii
SYMBOL TITLE
Fatigue strength of material used in beam fabrication Strain gauge factor
Ss Sensitivity of the strain gauge-Wheatstone bridge system
x Distance of gauge from effective load
Ω Ohm
Poisson’s ratio / Input/Source voltage
Output voltage
σ Stress
ε Strain
ε Transverse strain ε Longitudinal strain
Longitudinal force at device Lateral force at device Vertical force at device Rolling moment at device Overturning moment at device Self aligning moment at device Radius of tire
Length from the tire to the device Tire camber angle
y Value of a point at the y-axis x Value of a point at the x-axis m Gradient of the graph line
c A constant
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xviii
LIST OF APPENDICES
APPENDIX TITLE PAGE
A A novel six-axis force sensor for measuring
the loading of the racing tyre on track. 110
B A novel six-component force sensor of good
measurement isotropy and sensitivities. 117
C GUI menu concepts 125
D Data from calibration of the tire force
measuring device 128
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1
CHAPTER 1
INTRODUCTION
1.1 The Wheel Dynamic Test Rig
The wheel dynamic test rig is designed by Goh C. K., a degree undergraduate of Universiti Teknikal Malaysia Melaka (UTeM), in favor of his final year project or also known as ‘Projek Sarjana Muda’ (PSM). The purpose of the wheel dynamic test rig is to investigate the handling dynamics of a tire. The test rig is built based on a quarter car model which includes a supporting frame, wheel, shaft and a conveyor belt that simulates the road input on a spinning wheel. The belt on the conveyer is given roughness as to simulate a real tar road condition. The conveyor will be powered by an electric motor and will run at a desired linear speed of 60km/h.
The core of the test rig is a six-component force sensor. According to Sheng A. Liu and Hung L. Tzo (2002), a six-component force sensor is a unit which functions to simultaneously measure six forces of which are three orthogonal forces and three orthogonal moments and is used for wind-tunnel balances, thrust stand testing of rocket engines, automobiles, shipbuilding, and particularly quite common for adaptive real-time control purpose of machines such as robotic systems. The three orthogonal forces are longitudinal force ( ), lateral force ( ) and vertical force ( ) while the three orthogonal moments are divided into the rolling moment ( ), pitching moment ( ) and yawing moment ( ).
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2
The six-component force sensor is a small structure that is placed on the wheel shaft of the test rig. Strain gauges are installed on the six-component force sensor to detect strains and stresses experience by the structure of the six-component force sensor. The loads experienced by the tire will be transferred to the shaft itself and hence being interpreted by the six-component force sensor. Steering angle of the tire can be manipulated with adjustable settings in the test rig itself to investigate the handling dynamics and effects of the tire in various wheel settings.
The wiring of the strain gauges will imply the use of Wheatstone bridge. A data acquisition card is used to collect data from the force sensor and feed it to a personal computer for data conversion. The data are obtained and recorded in the personal computer. The computer program used to interpret these data is MATLAB with its sub program of Simulink, Data Acquisition Toolbox and GUIDE.
1.2 Design of the six-component force sensor.
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3
The design of Goh C. K.’s six-component force sensor is improvised from Sheng A. Liu and Hung L. Tzo’s original design. Strain gauges are placed on the positions indicated by numbers in Figure 1. There are a total of 12 strain gauges placed on the device.
1.3 User Interface
The author is responsible for the digital parts of the project. An interface is needed to bridge between the user and the six-component force sensor. The interface functions by translating the data and information acquired from the device into a more comprehendible output. The interface also provides user friendly features as the user would only key in the inputs and automatically, outputs will be generated with ease. Other important outputs such as graphs or other visual outputs can be generated automatically with a touch of a button. In this context, the forces and moments that are acting towards the tire cannot be measured using the naked eye. These parameters can only be detected using measuring devices and the user interface forms a visible bridge between these parameters and the user.
The User Interface (UI) or also known as Human Computer Interface is the aggregate of means that enables human to interact with the system. The system can be a particular machine, device, computer program or other complex tools. The user interface provides means of input which allows the users to manipulate the system and output which allows the system to produce the effects of the users' manipulation. Graphical User Interface (GUI) accepts input via devices such as computer keyboard and mouse and provides articulated graphical output on the computer monitor or digital display. Software is the shift from computation-intensive design to presentation-intensive design. As computers and machines have become more powerful throughout the decades, the steadily increasing fraction of that power is used to improve presentation. The software patterns shifted from computation-intensive design to presentation-computation-intensive design, such as GUI. The pattern progressions can be concluded into three eras: batch (1945-1968), command-line (1969-1983) and graphical (1984 - current). Other explanation on user interface is
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4
that a user interface is a linkage between a human and a device or system that allows the human to interact or exchange information with that device or system. An interface is a shared boundary or connection between two dissimilar objects, devices or systems through which information is passed and the connection can be either physical or logical.
The MATLAB programming language will be used to build the user interface. Raw data will be obtained and recorded via a sub program of MATLAB which is the Data Acquisition Toolbox. The data from the strain gauges, which are in terms of change of electrical resistances, ohm (Ω), will be converted into the three orthogonal forces and three orthogonal moments using the Wheatstone bridge and MATLAB program. The data from the strain gauge will be fed into the data acquisition card which is connected to a personal computer. The graphical user interface will be done using GUIDE which permits the user to input the duration of the force measurement process and obtain results in forms of tables and graphs.
1.4 Problem Statement
Building a user interface requires not only the comprehension of the MATLAB program, but also the logical equations in converting the data acquired from the strain gauges on the tire force measuring device. A user interface provides the data conversions function and graphical results. The possibilities of errors in the strain gauges used and the built-structure of the six-component force sensor need to be considered. The possible problems that might occur during the study are as follow:
i) The strain and stress experienced by each strain gauge for detecting the same force or moment might not be equal to each other due to errors in atomic level structure of the material used, the accuracy in the dimension of the device and strain gauge installation process. This can cause inaccuracy in data conversion.
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ii) The value of the data acquired from the six-component axis might be very small and negligible.
iii) The strain gauges may pick up unnecessary noise
1.5 Objectives of Study
It is crucial to overcome the problem statements mentioned or at least to minimize them in order to achieve the most accurate results possible.
i) To acquire data from the tire force measuring device through an instrumentation system.
ii) To convert the acquired data into respective forces and moments. iii) To design a user interface program.
1.6 Scope of Study
The scopes in this study include:
i) To design a graphical user interface for the tire force measuring device using GUIDE.
ii) To determine the most suitable method of data acquisition of the strain gauge.
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LIST OF APPENDICES
APPENDIX TITLE PAGE
A A novel six-axis force sensor for measuring
the loading of the racing tyre on track. 110
B A novel six-component force sensor of good
measurement isotropy and sensitivities. 117
C GUI menu concepts 125
D Data from calibration of the tire force
measuring device 128
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CHAPTER 1
INTRODUCTION
1.1 The Wheel Dynamic Test Rig
The wheel dynamic test rig is designed by Goh C. K., a degree undergraduate of Universiti Teknikal Malaysia Melaka (UTeM), in favor of his final year project or also known as ‘Projek Sarjana Muda’ (PSM). The purpose of the wheel dynamic test rig is to investigate the handling dynamics of a tire. The test rig is built based on a quarter car model which includes a supporting frame, wheel, shaft and a conveyor belt that simulates the road input on a spinning wheel. The belt on the conveyer is given roughness as to simulate a real tar road condition. The conveyor will be powered by an electric motor and will run at a desired linear speed of 60km/h.
The core of the test rig is a six-component force sensor. According to Sheng A. Liu and Hung L. Tzo (2002), a six-component force sensor is a unit which functions to simultaneously measure six forces of which are three orthogonal forces and three orthogonal moments and is used for wind-tunnel balances, thrust stand testing of rocket engines, automobiles, shipbuilding, and particularly quite common for adaptive real-time control purpose of machines such as robotic systems. The three orthogonal forces are longitudinal force ( ), lateral force ( ) and vertical force ( ) while the three orthogonal moments are divided into the rolling moment ( ), pitching moment ( ) and yawing moment ( ).
(3)
The six-component force sensor is a small structure that is placed on the wheel shaft of the test rig. Strain gauges are installed on the six-component force sensor to detect strains and stresses experience by the structure of the six-component force sensor. The loads experienced by the tire will be transferred to the shaft itself and hence being interpreted by the six-component force sensor. Steering angle of the tire can be manipulated with adjustable settings in the test rig itself to investigate the handling dynamics and effects of the tire in various wheel settings.
The wiring of the strain gauges will imply the use of Wheatstone bridge. A data acquisition card is used to collect data from the force sensor and feed it to a personal computer for data conversion. The data are obtained and recorded in the personal computer. The computer program used to interpret these data is MATLAB with its sub program of Simulink, Data Acquisition Toolbox and GUIDE.
1.2 Design of the six-component force sensor.
(4)
The design of Goh C. K.’s six-component force sensor is improvised from Sheng A. Liu and Hung L. Tzo’s original design. Strain gauges are placed on the positions indicated by numbers in Figure 1. There are a total of 12 strain gauges placed on the device.
1.3 User Interface
The author is responsible for the digital parts of the project. An interface is needed to bridge between the user and the six-component force sensor. The interface functions by translating the data and information acquired from the device into a more comprehendible output. The interface also provides user friendly features as the user would only key in the inputs and automatically, outputs will be generated with ease. Other important outputs such as graphs or other visual outputs can be generated automatically with a touch of a button. In this context, the forces and moments that are acting towards the tire cannot be measured using the naked eye. These parameters can only be detected using measuring devices and the user interface forms a visible bridge between these parameters and the user.
The User Interface (UI) or also known as Human Computer Interface is the aggregate of means that enables human to interact with the system. The system can be a particular machine, device, computer program or other complex tools. The user interface provides means of input which allows the users to manipulate the system and output which allows the system to produce the effects of the users' manipulation. Graphical User Interface (GUI) accepts input via devices such as computer keyboard and mouse and provides articulated graphical output on the computer monitor or digital display. Software is the shift from computation-intensive design to presentation-intensive design. As computers and machines have become more powerful throughout the decades, the steadily increasing fraction of that power is used to improve presentation. The software patterns shifted from computation-intensive design to presentation-computation-intensive design, such as GUI. The pattern progressions can be concluded into three eras: batch (1945-1968), command-line (1969-1983) and graphical (1984 - current). Other explanation on user interface is
(5)
that a user interface is a linkage between a human and a device or system that allows the human to interact or exchange information with that device or system. An interface is a shared boundary or connection between two dissimilar objects, devices or systems through which information is passed and the connection can be either physical or logical.
The MATLAB programming language will be used to build the user interface. Raw data will be obtained and recorded via a sub program of MATLAB which is the Data Acquisition Toolbox. The data from the strain gauges, which are in terms of change of electrical resistances, ohm (Ω), will be converted into the three orthogonal forces and three orthogonal moments using the Wheatstone bridge and MATLAB program. The data from the strain gauge will be fed into the data acquisition card which is connected to a personal computer. The graphical user interface will be done using GUIDE which permits the user to input the duration of the force measurement process and obtain results in forms of tables and graphs.
1.4 Problem Statement
Building a user interface requires not only the comprehension of the MATLAB program, but also the logical equations in converting the data acquired from the strain gauges on the tire force measuring device. A user interface provides the data conversions function and graphical results. The possibilities of errors in the strain gauges used and the built-structure of the six-component force sensor need to be considered. The possible problems that might occur during the study are as follow:
i) The strain and stress experienced by each strain gauge for detecting the same force or moment might not be equal to each other due to errors in atomic level structure of the material used, the accuracy in the dimension of the device and strain gauge installation process. This can cause inaccuracy in data conversion.
(6)
ii) The value of the data acquired from the six-component axis might be very small and negligible.
iii) The strain gauges may pick up unnecessary noise
1.5 Objectives of Study
It is crucial to overcome the problem statements mentioned or at least to minimize them in order to achieve the most accurate results possible.
i) To acquire data from the tire force measuring device through an instrumentation system.
ii) To convert the acquired data into respective forces and moments. iii) To design a user interface program.
1.6 Scope of Study
The scopes in this study include:
i) To design a graphical user interface for the tire force measuring device using GUIDE.
ii) To determine the most suitable method of data acquisition of the strain gauge.