A leading and authoritative text for advancing ground vehicle mobility
Theory of Ground Vehicles, Fifth Edition presents updated and expanded coverage of the critical factors affecting the performance, handling, and ride essential to the development and design of road and off-road vehicles.
Replacing internal combustion engines with zero-emission powerplants in ground vehicles to eliminate greenhouse gas emissions for curbing climate change has received worldwide attention by both the vehicle industry and governmental agencies. To enhance safety, traffic flow, and operating efficiency of road transport, automated driving systems have been under active development. With growing interest in the exploration of the Moon, Mars, and beyond, research in terramechanics for guiding the development of extraterrestrial rovers has been intensified. In this new edition, these and other topics of interest in the field of ground vehicle technology are explored, and technical data are updated. New features of this edition include: - Expanded coverage of the fundamentals of electric drives, hybrid electric drives, and fuel cell technology - Introduction to the classification and operating principles of the automated driving system and cooperative driving automation - Applications of terramechanics to guiding the development of extraterrestrial rovers - Elaboration on the approach to achieving the optimal operating efficiency of all-wheel drive off-road vehicles - Introduction to updated ISO Standards for evaluating vehicle ride
An updated and comprehensive text and reference for both the educational and professional communities, Theory of Ground Vehicles, Fifth Edition will prove invaluable to aspiring and practicing engineers seeking to solve real-world road and off-road vehicle mobility problems.
Table of Contents
Author Biography xiii
Preface to the Fifth Edition xv
Preface to the Fourth Edition xvii
Preface to the Third Edition xix
Preface to the Second Edition xxi
Preface to the First Edition xxiii
Conversion Factors xxv
Abbreviations and Acronyms xxvii
List of Symbols xxix
Introduction xxxix
About the Companion Website xli
1 Mechanics of Pneumatic Tires 1
1.1 Tire Forces and Moments 6
1.2 Rolling Resistance of Tires 7
1.3 Tractive (Braking) Effort and Longitudinal Slip (Skid) 15
1.3.1 Tractive Effort and Longitudinal Slip 15
1.3.2 Braking Effort and Longitudinal Skid 22
1.4 Cornering Properties of Tires 27
1.4.1 Slip Angle and Cornering Force 27
1.4.2 Slip Angle and Aligning Torque 32
1.4.3 Camber and Camber Thrust 34
1.4.4 Characterization of Cornering Behavior of Tires 37
1.4.5 The Magic Formula 49
1.5 Performance of Tires on Wet Surfaces 55
1.6 Ride Properties of Tires 61
1.7 Tire/Road Noise 71
References 74
Problems 75
2 Mechanics of Vehicle-Terrain Interaction: Terramechanics 77
2.1 Applications of the Theory of Elasticity to Predicting Stress Distributions in the Terrain under Vehicular Loads 78
2.2 Applications of the Theory of Plastic Equilibrium to the Mechanics of Vehicle-Terrain Interaction 84
2.3 Empirically Based Models for Predicting Off-Road Vehicle Mobility 99
2.3.1 NATO Reference Mobility Model (NRMM) 99
2.3.2 Empirical Models for Predicting Single Wheel Performance 106
2.3.3 Empirical Models Based on the Mean Maximum Pressure 108
2.3.4 Limitations and Prospects for Empirically Based Models 111
2.4 Measurement and Characterization of Terrain Response 114
2.4.1 Characterization of Pressure-Sinkage Relationships 116
2.4.2 Characterization of the Response to Repetitive Normal Loading 124
2.4.3 Characterization of Shear Stress-Shear Displacement Relationships 126
2.4.4 Characterization of the Response to Repetitive Shear Loading 132
2.4.5 Bekker-Wong Terrain Parameters 133
2.5 A Simplified Physics-Based Model for the Performance of Tracked Vehicles 134
2.5.1 Motion Resistance of a Track 135
2.5.2 Tractive Effort and Slip of a Track 137
2.6 An Advanced Physics-Based Model for the Performance of Vehicles with Flexible Tracks 142
2.6.1 Approach to the Prediction of Normal Pressure Distribution under a Track 143
2.6.2 Approach to the Prediction of Shear Stress Distribution under a Track 145
2.6.3 Prediction of Motion Resistance and Drawbar Pull as Functions of Track Slip 146
2.6.4 Experimental Substantiation 147
2.6.5 Applications to Parametric Analysis and Design Optimization 148
2.7 An Advanced Physics-Based Model for the Performance of Vehicles with Long-Pitch Link Tracks 157
2.7.1 Basic Approach 157
2.7.2 Experimental Substantiation 158
2.7.3 Applications to Parametric Analysis and Design Optimization 160
2.8 Physics-Based Models for the Cross-Country Performance of Wheels (Tires) 163
2.8.1 Motion Resistance of a Rigid Wheel 163
2.8.2 Motion Resistance of a Pneumatic Tire 166
2.8.3 Tractive Effort and Slip of a Wheel (Tire) 171
2.9 A Physics-Based Model for the Performance of Off-Road Wheeled Vehicles 175
2.9.1 Basic Approach 175
2.9.2 Experimental Substantiation 176
2.9.3 Applications to Parametric Analysis 177
2.10 Slip Sinkage 178
2.10.1 Physical Nature of Slip Sinkage 178
2.10.2 Simplified Methods for Predicting Slip Sinkage 180
2.11 Applications of Terramechanics to the Study of Mobility of Extraterrestrial Rovers and their Running Gears 185
2.11.1 Predicting the Performance of Rigid Rover Wheels on Extraterrestrial Surfaces Based on Test Results Obtained on Earth 185
2.11.2 Performances of Lunar Roving Vehicle Flexible Wheels Predicted Using the Model NWVPM and Correlations with Test Data 198
2.12 Finite Element and Discrete Element Methods for the Study of Vehicle-Terrain Interaction 202
2.12.1 The Finite Element Method 203
2.12.2 The Discrete (Distinct) Element Method 207
References 212
Problems 218
3 Performance Characteristics of Road Vehicles 221
3.1 Equation of Motion and Maximum Tractive Effort 221
3.2 Aerodynamic Forces and Moments 225
3.3 Internal Combustion Engines 239
3.3.1 Performance Characteristics of the Internal Combustion Engine 240
3.3.2 Emissions of Internal Combustion Engines 246
3.4 Electric Drives 248
3.4.1 Elements of an Electric Drive 251
3.4.2 Characteristics of Battery Electric Passenger Vehicles 255
3.5 Hybrid Electric Drives 256
3.5.1 Types of Hybrid Electric Drive 257
3.5.2 Characteristics of Energy Consumption and Emissions of Hybrid Electric Vehicles 270
3.6 Fuel Cells 273
3.6.1 Polymer Electrolyte Membrane Fuel Cells 274
3.6.2 Characteristics of Fuel Cell Vehicles 277
3.7 Transmissions for Vehicles with Internal Combustion Engines 278
3.7.1 Manual Gear Transmissions 279
3.7.2 Automatic Transmissions 287
3.7.3 Continuously Variable Transmissions 294
3.7.4 Hydrostatic Transmissions 296
3.8 Prediction of Vehicle Performance 298
3.8.1 Acceleration Time and Distance 299
3.8.2 Gradeability 301
3.9 Operating Fuel Economy of Vehicles with Internal Comustion Engines 302
3.10 Internal Combustion Engine and Transmission Matching 316
3.11 Braking Performance 319
3.11.1 Braking Characteristics of a Two-Axle Vehicle 319
3.11.2 Braking Efficiency and Stopping Distance 327
3.11.3 Braking Characteristics of a Tractor-Semitrailer 329
3.11.4 Antilock Brake Systems 332
3.11.5 Traction Control Systems 337
References 338
Problems 342
4 Performance Characteristics of Off-Road Vehicles 345
4.1 Drawbar Performance 346
4.1.1 Drawbar Pull and Drawbar Power 346
4.1.2 Drawbar (Tractive) Efficiency 350
4.1.3 All-Wheel Drive 354
4.1.4 Coefficient of Traction 364
4.1.5 Weight-to-Power Ratio for Off-Road Vehicles 364
4.2 Fuel Economy of Cross-Country Operations 366
4.3 Transport Productivity and Transport Efficiency 368
4.4 Mobility Map and Mobility Profile 369
4.5 Selection of Vehicle Configurations for Off-Road Operations 372
4.5.1 Wheeled Vehicles 373
4.5.2 Tracked Vehicles 373
4.5.3 Wheeled Vehicles versus Tracked Vehicles 374
References 378
Problems 379
5 Handling Characteristics of Road Vehicles 381
5.1 Steering Geometry 381
5.2 Steady-State Handling Characteristics of a Two-Axle Vehicle 384
5.2.1 Neutral Steer 387
5.2.2 Understeer 387
5.2.3 Oversteer 388
5.3 Steady-State Response to Steering Input 393
5.3.1 Yaw Velocity Response 393
5.3.2 Lateral Acceleration Response 394
5.3.3 Curvature Response 394
5.4 Testing of Handling Characteristics 397
5.4.1 Constant Radius Test 397
5.4.2 Constant Speed Test 398
5.4.3 Constant Steer Angle Test 399
5.5 Transient Response Characteristics 400
5.6 Directional Stability 403
5.6.1 Criteria for Directional Stability 403
5.6.2 Vehicle Stability Control 406
5.7 Driving Automation 412
5.7.1 Classification of Levels of Driving Automation 413
5.7.2 Automated Driving Systems and Cooperative Driving Automation 415
5.8 Steady-State Handling Characteristics of a Tractor-Semitrailer 417
5.9 Simulation Models for the Directional Behavior of Articulated Road Vehicles 421
5.9.1 The Linear Yaw Plane Model 421
5.9.2 TBS Model 421
5.9.3 Yaw/Roll Model 422
5.9.4 The Phase 4 Model 422
5.9.5 Summary 423
References 428
Problems 430
6 Steering of Tracked Vehicles 433
6.1 Simplified Analysis of the Kinetics of Skid-Steering 435
6.2 Kinematics of Skid-Steering 439
6.3 Skid-Steering at High Speeds 441
6.4 A General Theory for Skid-Steering on Firm Ground 444
6.4.1 Shear Displacement on the Track-Ground Interface 445
6.4.2 Kinetics in a Steady-State Turning Maneuver 449
6.4.3 Experimental Substantiation 452
6.4.4 Coefficient of Lateral Resistance 455
6.5 Power Consumption of Skid-Steering 457
6.6 Skid Steering Systems for Tracked Vehicles 458
6.6.1 Clutch/Brake Steering System 458
6.6.2 Controlled Differential Steering System 459
6.6.3 Planetary Gear Steering System 460
6.7 Articulated Steering 462
References 465
Problems 466
7 Vehicle Ride Characteristics 469
7.1 Human Response to Vibration 469
7.1.1 International Standard ISO 2631/1:1985 472
7.1.2 International Standard ISO 2631-1 : 1997/Amd.1 : 2010 474
7.1.3 Absorbed Power 480
7.2 Vehicle Ride Models 481
7.2.1 Two-Degrees-of-Freedom Vehicle Model for Vertical Vibrations of Sprung and Unsprung Mass 482
7.2.2 Numerical Methods for Determining the Response of a Quarter-Car Model to Irregular Surface Profile Excitation 494
7.2.3 Two-Degrees-of-Freedom Vehicle Model for Pitch and Bounce 497
7.3 Introduction to Random Vibration 501
7.3.1 Surface Elevation Profile as a Random Function 501
7.3.2 Frequency Response Function 507
7.3.3 Evaluation of Vehicle Vibration in Relation to Ride Comfort Criteria 509
7.4 Active and Semi-Active Suspensions 510
7.4.1 Active Suspensions 511
7.4.2 Semi-Active Suspensions 512
References 517
Problems 519
8 Introduction to Air-Cushion Vehicles 521
8.1 Air-Cushion Systems and their Performances 521
8.1.1 Plenum Chambers 521
8.1.2 Peripheral Jets 528
8.2 Resistances of Air-Cushion Vehicles 531
8.2.1 Momentum Drag 531
8.2.2 Trim Drag 532
8.2.3 Skirt Contact Drag 532
8.2.4 Total Overland Drag 535
8.2.5 Wave-Making Drag 537
8.2.6 Wetting Drag 539
8.2.7 Drag Due to Waves 540
8.2.8 Total Overwater Drag 540
8.3 Suspension Characteristics of Air-Cushion Systems 542
8.3.1 Heave (or Bounce) Stiffness 542
8.3.2 Roll and Pitch Stiffness 545
8.4 Directional Control of Air-Cushion Vehicles 546
References 549
Problems 550
Index 553
