Automotive Chassis Engineering

337 Pages·2018·13.82 MB·English

by  David C Barton

David C. Barton
John D. Fieldhouse
Automotive
Chassis
Engineering
Automotive Chassis Engineering
David C. Barton John D. Fieldhouse
(cid:129)
Automotive Chassis
Engineering
123
DavidC. Barton JohnD.Fieldhouse
Schoolof MechanicalEngineering Schoolof MechanicalEngineering
University of Leeds University of Leeds
Leeds Leeds
UK UK
ISBN978-3-319-72436-2 ISBN978-3-319-72437-9 (eBook)
https://doi.org/10.1007/978-3-319-72437-9
LibraryofCongressControlNumber:2018931474
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Preface
A common concern of the automotive industry is that new recruits/graduates are
more than able to operate the modern computer-aided design packages but are not
fully aware or knowledgeable about the basic theory within the programmes.
Because of that lack of basic understanding, they are unable to develop the com-
mercial package(s) to suit the company’s needs nor readily appreciate the output
values.Evenmoreimportant,astimeprogressesandthatbasicknowledgebecomes
rarer within companies, the reliance on commercial software suppliers increases,
alongwithcosts.Thereisacontinuingneedforcompaniestobecomeself-sufficient
and be in a position to develop bespoke design ‘tools’ specific to their needs.
The advances in electric vehicle technology and move towards autonomous
drivingmakeitnecessaryfortheengineertocontinuallyupgradetheirfundamental
understanding and interrelationship of vehicle systems. The engineers in their
formativeyearsoftrainingneedtobeinapositiontocontributetothedevelopment
ofnewsystemsandindeedrealisenewones.Tomakeacontributionitisnecessary
to, again, understand the technology and fundamental understanding of vehicle
systems.
This textbook is written for students and practicing engineers working or
interestedinautomotiveengineering.Itprovidesafundamentalyetcomprehensive
understandingofchassissystemsandpresumeslittlepriorknowledgebythereader
beyond that normally presented in Bachelor level courses in mechanical or auto-
motive engineering. The book presents the material in a practical and realistic
manner, often using reverse engineering as a basis for examples to reinforce
understanding of the topics. Existing vehicle specifications and characteristics are
used to exemplify the application of theory. Each chapter starts with a review of
basic theory and practice before proceeding to consider more advanced topics and
research directions. Care is taken to ensure each subject area integrates with other
sections of the book to clearly demonstrate their interrelationships.
The book opens with a chapter on basic vehicle mechanics which indicates the
forces acting on a vehicle in motion, assuming the vehicle to be a rigid body.
Althoughthismaterialwillbefamiliartomanyreaders,itisanecessaryprerequisite
tothemorespecialistmaterialthatfollows.Thebookthenproceedstoachapteron
v
vi Preface
steering systems which includes a firm understanding of the principles and forces
involved under both static and dynamic loading. The next chapter provides an
appreciationofvehicledynamicsthroughtheconsiderationofsuspensionsystems—
tyres, linkages, springs, dampers, etc. The chassis structures and materials chapter
includes analysis tools (typically FEA) and design features that are used on modern
vehiclestoreducemassandtoincreaseoccupantsafety.ThefinalchapteronNoise,
VibrationandHarshness(NVH)includesabasicoverviewofacousticandvibration
theory and makes use of extensive research investigations and test procedures as a
means to alleviate NVH issues.
In all subject areas, the authors take account of modern trends, anticipating the
movetowardselectricvehicles,on-boarddiagnosticmonitoring,activesystemsand
performance optimisation. The book contains a number of worked examples and
case studies based on recent research projects. All students, especially those on
MastersleveldegreecoursesinAutomotiveEngineering,aswellasprofessionalsin
industrywhowanttogainabetterunderstandingofvehiclechassisengineeringwill
benefit from this book.
Leeds, UK David C. Barton
John D. Fieldhouse
Acknowledgements
TheoriginsofthisbooklieinacourseofthesamenamedeliveredtoMasterslevel
Automotive and Mechanical Engineering students at the University of Leeds for a
number of years. The authors are grateful to those who have contributed to the
design and development of the course, especially the late Professor David Crolla,
Professor David Towers, Dr. Brian Hall and Dr. Peter Brooks, as well as to
previous research students who have developed some of the case study material.
vii
Contents
1 Vehicle Mechanics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Modelling Philosophy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Co-ordinate Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Tractive Force and Tractive Resistance . . . . . . . . . . . . . . . . . . . 3
1.3.1 Tractive Force or Tractive Effort (TE). . . . . . . . . . . . . . 3
1.3.2 Tractive Resistances (TR). . . . . . . . . . . . . . . . . . . . . . . 4
1.3.3 Effect of TR and TE on Vehicle Performance . . . . . . . . 12
1.4 Tyre Properties and Performance. . . . . . . . . . . . . . . . . . . . . . . . 14
1.4.1 Tyre Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.4.2 Tyre Designation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.4.3 The Friction Circle. . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.4.4 Limiting Frictional Force Available. . . . . . . . . . . . . . . . 19
1.5 Rigid Body Load Transfer Effects for Straight Line Motion . . . . 21
1.5.1 Vehicle Stationary or Moving at Constant
Velocity on Sloping Ground. . . . . . . . . . . . . . . . . . . . . 21
1.5.2 Vehicle Accelerating/Decelerating on Level Ground. . . . 22
1.5.3 Rear Wheel, Front Wheel and Four Wheel Drive
Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.5.4 Caravans and Trailers. . . . . . . . . . . . . . . . . . . . . . . . . . 28
1.6 Rigid Body Load Transfer Effects During Cornering . . . . . . . . . 35
1.6.1 Steady State Cornering. . . . . . . . . . . . . . . . . . . . . . . . . 37
1.6.2 Non-steady State Cornering . . . . . . . . . . . . . . . . . . . . . 38
1.7 Concluding Remarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
2 Steering Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.1 General Aims and Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
2.2 Steering Requirements/Regulations . . . . . . . . . . . . . . . . . . . . . . 46
2.2.1 General Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . 46
2.2.2 Steering Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.2.3 Steering Behaviour. . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
ix
x Contents
2.3 Steering Geometry and Kinematics . . . . . . . . . . . . . . . . . . . . . . 49
2.3.1 Basic Design Needs . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.3.2 Ideal Ackermann Steering Geometry . . . . . . . . . . . . . . . 51
2.4 Review of Common Designs. . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.4.1 Manual Steering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.4.2 Rack and Pinion System. . . . . . . . . . . . . . . . . . . . . . . . 54
2.4.3 Steering Box Systems. . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.4.4 Hydraulic Power Assisted Steering (HPAS). . . . . . . . . . 58
2.4.5 Electric Power Assisted Steering (EPAS). . . . . . . . . . . . 60
2.4.6 Steer-by-Wire. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
2.5 Steering “Errors” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
2.5.1 Tyre Slip and Tyre Slip Angle . . . . . . . . . . . . . . . . . . . 66
2.5.2 Compliance Steer—Elastokinematics. . . . . . . . . . . . . . . 68
2.5.3 Steering Geometry Errors . . . . . . . . . . . . . . . . . . . . . . . 72
2.6 Important Geometric Parameters in Determining Steering
Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
2.6.1 Front Wheel Geometry. . . . . . . . . . . . . . . . . . . . . . . . . 73
2.6.2 Kingpin Inclination Angle (Lateral
Inclination Angle) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
2.6.3 Castor Inclination Angle (Mechanical Castor) . . . . . . . . 75
2.7 Forces Associated with Steering a Stationary Vehicle . . . . . . . . . 77
2.7.1 Tyre Scrub. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
2.7.2 Jacking of the Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . 80
2.7.3 Forces at the Steering Wheel . . . . . . . . . . . . . . . . . . . . 83
2.8 Forces Associated with Steering a Moving Vehicle. . . . . . . . . . . 91
2.8.1 Normal Force. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
2.8.2 Lateral Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
2.8.3 Longitudinal Force—Tractive Effort
(Front Wheel Drive) or Braking . . . . . . . . . . . . . . . . . . 100
2.8.4 Rolling Resistance and Overturning Moments . . . . . . . . 101
2.9 Four Wheel Steering (4WS) . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
2.10 Developments in Steering Assistance—Active Torque
Dynamics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
2.10.1 Active Yaw Damping. . . . . . . . . . . . . . . . . . . . . . . . . . 109
2.10.2 Active Torque Input. . . . . . . . . . . . . . . . . . . . . . . . . . . 109
2.11 Concluding Remarks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
3 Suspension Systems and Components. . . . . . . . . . . . . . . . . . . . . . . . 111
3.1 Introduction to Suspension Design. . . . . . . . . . . . . . . . . . . . . . . 111
3.1.1 The Role of a Vehicle Suspension. . . . . . . . . . . . . . . . . 112
3.1.2 Definitions and Terminology. . . . . . . . . . . . . . . . . . . . . 113
3.1.3 What Is a Vehicle Suspension?. . . . . . . . . . . . . . . . . . . 113
3.1.4 Suspension Classifications . . . . . . . . . . . . . . . . . . . . . . 114
Contents xi
3.1.5 Defining Wheel Position. . . . . . . . . . . . . . . . . . . . . . . . 115
3.1.6 Tyre Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
3.2 Selection of Vehicle Suspensions. . . . . . . . . . . . . . . . . . . . . . . . 122
3.2.1 Factors Influencing Suspension Selection. . . . . . . . . . . . 123
3.3 Kinematic Requirements for Dependent and Independent
Suspensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
3.3.1 Examples of Dependent Suspensions. . . . . . . . . . . . . . . 125
3.3.2 Examples of Independent Front Suspensions . . . . . . . . . 128
3.3.3 Examples of Independent Rear Suspensions. . . . . . . . . . 130
3.3.4 Examples of Semi-independent Rear Suspensions . . . . . 132
3.4 Springs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
3.4.1 Spring Types and Characteristics. . . . . . . . . . . . . . . . . . 135
3.4.2 Anti-roll Bars (Roll Stabilisers). . . . . . . . . . . . . . . . . . . 143
3.5 Dampers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151
3.5.1 Damper Types and Characteristics. . . . . . . . . . . . . . . . . 151
3.5.2 Active Dampers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
3.6 Kinematic Analysis of Suspensions . . . . . . . . . . . . . . . . . . . . . . 157
3.7 Roll Centres and Roll Axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
3.7.1 Roll Centre Determination . . . . . . . . . . . . . . . . . . . . . . 163
3.7.2 Roll Centre Migration . . . . . . . . . . . . . . . . . . . . . . . . . 166
3.8 Lateral Load Transfer Due to Cornering. . . . . . . . . . . . . . . . . . . 168
3.8.1 Load Transfer Due to Roll Moment . . . . . . . . . . . . . . . 170
3.8.2 Load Transfer Due to Sprung Mass Inertia Force. . . . . . 171
3.8.3 Load Transfer Due to Unsprung Mass Inertia Forces . . . 171
3.8.4 Total Load Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
3.8.5 Roll Angle Gradient (Roll Rate) . . . . . . . . . . . . . . . . . . 172
3.9 Spring Rate and Wheel Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
3.9.1 Wheel Rate Required for Constant Natural
Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
3.9.2 The Relationship Between Spring
Rate and Wheel Rate . . . . . . . . . . . . . . . . . . . . . . . . . . 178
3.10 Analysis of Forces in Suspension Members . . . . . . . . . . . . . . . . 180
3.10.1 Longitudinal Loads Due to Braking
and Accelerating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
3.10.2 Vertical Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
3.10.3 Lateral, Longitudinal and Mixed Loads . . . . . . . . . . . . . 186
3.10.4 Limit or Bump Stops . . . . . . . . . . . . . . . . . . . . . . . . . . 188
3.10.5 Modelling Transient Loads . . . . . . . . . . . . . . . . . . . . . . 190
3.11 Suspension Geometry to Combat Squat and Dive. . . . . . . . . . . . 190
3.11.1 Anti-dive Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
3.11.2 Anti-squat Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . 195
3.12 Vehicle Ride Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201