A. GALIP ULSOY | HUEI PENG | MELIH ÇAKMAKCI

AUTOMOTIVE CONTROL SYSTEMS

AUTOMOTIVE CONTROL SYSTEMS This engineering textbook is designed to introduce advanced control systems for vehicles, including advanced automotive concepts and the next generation of vehicles for Intelligent Transportation Systems (ITS). For each automotive-control problem considered, the authors emphasize the physics and underlying principles behind the control-system concept and design. This is an exciting and rapidly developing field for which many articles and reports exist but no modern unifying text. An extensive list of references is provided at the end of each chapter for all topics covered. This is currently the only textbook, including problems and examples, that covers and integrates the topics of automotive powertrain control, vehicle control, and ITS. The emphasis is on fundamental concepts and methods for automotive control systems rather than the rapidly changing specific technologies. Many of the text examples, as well as the end-of-chapter problems, require the use of MATLAB and/or Simulink. A. Galip Ulsoy is the C. D. Mote Jr. Distinguished University Professor and the William Clay Ford Professor of Manufacturing at the University of Michigan. He served as director of the Ground Robotics Reliability Center and deputy director of the Engineering Research Center for Reconfigurable Manufacturing Systems. He has been on the faculty of the Department of Mechanical Engineering at Michigan since 1980 and was the founding director of the Program in Manufacturing. He served as technical editor of the American Society of Mechanical Engineers’ (ASME) Journal of Dynamic Systems, Measurement, and Control and is the founding technical editor of the ASME Dynamic Systems and Control Magazine. Professor Ulsoy is a member of the National Academy of Engineering and a Fellow of the ASME, the International Federation of Automatic Control, and the Society of Manufacturing Engineers; a Senior Member of IEEE; and a member of several other professional and honorary organizations. He is the past president of the American Automatic Control Council. He co-authored, with Warren R. DeVries, Microcomputer Applications in Manufacturing, and he is a co-author, with Sun Yi and Patrick W. Nelson, of Time Delay Systems. He has published more than 300 refereed technical articles in journals, conferences, and books. Huei Peng is a Professor in the Department of Mechanical Engineering at the University of Michigan. He served as the executive director of interdisciplinary and professional engineering programs. His research interests include vehicle dynamics and control, electromechanical systems, optimal control, human-driver modeling, vehicle active-safety systems, control of hybrid and fuel-cell vehicles, energy-system design, and control for mobile robots. He has received numerous awards and honors, including the ChangJiang Scholar Award, Tsinghua University; a 2008 Fellow of the ASME; the Outstanding Achievement Award, Mechanical Engineering Department, University of Michigan (2005); the Best Paper Award, 7th International Symposium on Advanced Vehicle Control (2004); and the CAREER Award, National Science Foundation (July 1998–June 2002). He has published more than 200 refereed technical articles in journals, conferences, and books. Professor Peng is co-editor of Advanced Automotive Technologies with J. S. Freeman and co-author of Control of Fuel Cell Power Systems – Principles, Modeling, Analysis and Feedback Design, with Jay T. Pukrushpan and Anna G. Stefanopoulou. Melih C ¸ akmakcı is a professor of Mechanical Engineering at Bilkent University in Ankara, Turkey. His research areas include modeling, analysis and control of dynamic systems, control systems, smart mechatronics, modeling of manufacturing systems and their control, automotive control systems, optimal energy-management algorithms, and design and analysis of network control systems. Prior to joining Bilkent University, he was a senior engineer at the Ford Scientific Research Center.

Automotive Control Systems A. Galip Ulsoy University of Michigan

Huei Peng University of Michigan

Melih C ¸ akmakcı Bilkent University

University Printing House, Cambridge CB2 8BS, United Kingdom One Liberty Plaza, 20th Floor, New York, NY 10006, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia 314-321, 3rd Floor, Plot 3, Splendor Forum, Jasola District Centre, New Delhi - 110025, India 79 Anson Road, #06-04/06, Singapore 079906 Cambridge University Press is part of the University of Cambridge. It furthers the University’s mission by disseminating knowledge in the pursuit of education, learning and research at the highest international levels of excellence. www.cambridge.org Information on this title: www.cambridge.org/9781107010116 © A. Galip Ulsoy, Huei Peng, and Melih Çakmakcı 2012 This publication is in copyright. Subject to statutory exception and to the provisions of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published 2012 A catalogue record for this publication is available from the British Library Library of Congress Cataloging in Publication data Ulsoy, Ali Galip. Automotive control systems / A. Galip Ulsoy, University of Michigan, Huei Peng, University of Michigan, Melih Çakmakci, Bilkent University. p. cm. Includes index. ISBN 978-1-107-01011-6 (hardback) 1. Automobiles – Automatic control. 2. Adaptive control systems. 3. Automobiles – Motors – Control systems. I. Peng, Huei. II. Çakmakci, Melih. III. Title. TL152.8.U47 2012 629.25´8–dc23 2011052559 ISBN 978-1-107-01011-6 Hardback ISBN 978-1-107-68604-5 Paperback Cambridge University Press has no responsibility for the persistence or accuracy of URLs for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate.

Contents

Preface

page ix

PART I INTRODUCTION AND BACKGROUND

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Motivation, Background, and Overview 1.2 Overview of Automotive Control Systems

3 7

2 Automotive Control-System Design Process . . . . . . . . . . . . . . . . . . . 21 2.1 Introduction 2.2 Identifying the Control Requirements

21 22

3 Review of Engine Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.1 Engine Operations 3.2 Engine Control Loops 3.3 Control-Oriented Engine Modeling

33 37 42

4 Review of Vehicle Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 4.1 4.2 4.3 4.4

Coordinates and Notation for Vehicle Dynamics Longitudinal Vehicle Motion Lateral Vehicle Motion Vertical Vehicle Motion

54 58 64 77

5 Human Factors and Driver Modeling . . . . . . . . . . . . . . . . . . . . . . . . . 93 5.1 Human Factors in Vehicle Automation 5.2 Driver Modeling

93 101

PART II POWERTRAIN CONTROL SYSTEMS

6 Air–Fuel Ratio Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119 6.1 Lambda Control 6.2 PI Control of a First-Order System with Delay

119 120

7 Control of Spark Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124 7.1 Knock Control

124 v

vi

Contents

8 Idle-Speed Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 9 Transmission Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 9.1 Electronic Transmission Control 9.2 Clutch Control for AWD

131 133

10 Control of Hybrid Vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 10.1 10.2 10.3 10.4 10.5 10.6

Series, Parallel, and Split Hybrid Configurations Hybrid Vehicle-Control Hierarchy Control Concepts for Series Hybrids Control Concepts for Parallel Hybrids Control Concept for Split Hybrids Feedback-Based Supervisory Controller for PHEVs

148 152 157 166 177 178

11 Modeling and Control of Fuel Cells for Vehicles . . . . . . . . . . . . . . . . 187 11.1 11.2 11.3 11.4 11.5

Introduction Modeling of Fuel-Cell Systems Control of Fuel-Cell Systems Control of Fuel-Cell Vehicles Parametric Design Considerations

187 189 196 201 205

PART III VEHICLE CONTROL SYSTEMS

12 Cruise and Headway Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 12.1 Cruise-Controller Design 12.2 Autonomous Cruise Control: Speed and Headway Control

213 224

13 Antilock Brake and Traction-Control Systems . . . . . . . . . . . . . . . . . 232 13.1 Modeling 13.2 Antilock Braking Systems 13.3 Traction Control

234 236 247

14 Vehicle Stability Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257 14.1 14.2 14.3 14.4

Introduction Linear Vehicle Model Nonlinear Vehicle Model VSC Design Principles

258 261 263 266

15 Four-Wheel Steering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272 15.1 Basic Properties 15.2 Goals of 4WS Algorithms

272 274

16 Active Suspensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287 16.1 Optimal Active Suspension for Single-DOF Model 16.2 Optimal Active Suspension for Two-DOF Model 16.3 Optimal Active Suspension with State Estimation

288 290 294

Contents

vii

PART IV INTELLIGENT TRANSPORTATION SYSTEMS

17 Overview of Intelligent Transportation Systems . . . . . . . . . . . . . . . . 309 17.1 17.2 17.3 17.4

Advanced Traffic Management Systems Advanced Traveler Information Systems Commercial Vehicle Operations Advanced Vehicle-Control Systems

310 312 314 314

18 Preventing Collisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322 18.1 Active Safety Technologies 18.2 Collision Detection and Avoidance

322 322

19 Longitudinal Motion Control and Platoons . . . . . . . . . . . . . . . . . . . . 332 19.1 Site-Specific Information 19.2 Platooning 19.3 String Stability

332 337 343

20 Automated Steering and Lateral Control . . . . . . . . . . . . . . . . . . . . . 348 20.1 Lane Sensing 20.2 Automated Lane-Following Control 20.3 Automated Lane-Change Control

348 352 356

APPENDICES

Appendix A: Review of Control-Theory Fundamentals . . . . . . . . . . . . . . 363 A.1 Review of Feedback Control A.2 Mathematical Background and Design Techniques

363 370

Appendix B: Two-Mass Three-Degree-of-Freedom Vehicle Lateral/Yaw/Roll Model . . . . . . . . . . . . . . . . . . . . . . . . . . 385 Index

391

Preface

This textbook is organized in four major parts as follows: I. Introduction and Background is an introduction to the topic of automotive control systems and a review of background material on engine modeling, vehicle dynamics, and human factors. II. Powertrain Control Systems includes topics such as air–fuel ratio control, idlespeed control, spark-timing control, control of transmissions, control of hybridelectric vehicles, and fuel-cell vehicle control. III. Vehicle Control Systems covers cruise control and headway-control systems, traction-control systems (including antilock brakes), active suspensions, vehiclestability control, and four-wheel steering. IV. Intelligent Transportation Systems (ITS) includes an overview of ITS technologies, collision detection and avoidance systems, automated highways, platooning, and automated steering. With multiple chapters in each part, this textbook contains sufficient material for a one-semester course on automotive control systems. The coverage of the material is at the first-year graduate or advanced undergraduate level in engineering. It is assumed that students have a basic undergraduate-level background in dynamics, automatic control, and automotive engineering. This textbook is written for engineering students who are interested in participating in the development of advanced control systems for vehicles, including advanced automotive concepts and the next generation of vehicles for ITS. This is an exciting and rapidly developing field for which numerous articles and reports exist. An extensive list of references, therefore, is provided at the end of each chapter for all topics covered. Due to the breadth of topics treated, the reference lists are by no means comprehensive, and new studies are always appearing. However, the lists cover many major contributions and the basic concepts in each sub-area. This textbook is intended to provide a framework for unifying the vast literature represented by the references listed at the end of each chapter. It is currently the only textbook, including problems and examples, that covers and integrates the topics of automotive powertrain control, vehicle control, and ITS. The emphasis is on fundamental concepts and methods for automotive control systems rather than the rapidly changing specific technologies. For each ix

x

Preface

automotive-control problem considered, we emphasize the physics and underlying principles behind the control-system concept and design. Any one of the many topics covered (e.g., engine control, vehicle-stability control, or platooning) could be discussed in more detail. However, rather than treating a specific control problem in its full complexity, we use each automotive control application as an opportunity to focus on a key engineering aspect of the control-design problem. For example, we discuss the importance of regulating the air–fuel ratio in engine control, the benefits for vehicle dynamics of reducing the vehicle side-slip angle in four-wheel steering and vehicle-stability control, the importance of predictive/preview action in the material on driver modeling, the concept of string stability for platoons and autonomous cruise-control systems, and the role of risk homeostasis in active-safetysystems design. We also use various automotive-control applications to focus on specific control methodologies. For example, the Smith predictor for control of time-delay systems is introduced in air–fuel ratio control; linear quadratic optimal estimation and control is introduced for active suspensions; adaptive control using recursive least squares estimation is introduced in the chapter on cruise-control systems; and sliding-mode control is introduced in the discussion of traction-control systems. However, all of these methods can be applied to many other automotive-control problems. End-of-chapter problems are included and many are used in our courses as homework and/or examination problems. Throughout the text, we include examples to illustrate key points. Many of these examples, as well as the end-of-chapter problems, require the use of MATLAB and/or Simulink. It is assumed that students are familiar with these computational engineering tools; for those who are not, we highly recommend the Control Tutorials for MATLAB and Simulink Web site (www.engin.umich.edu/class/ctms) for self-study. This textbook is based on course notes originally developed by A. Galip Ulsoy during the mid-1990s, then refined and added to by both Ulsoy and Huei Peng during a period of fifteen years of teaching this material to beginning graduate students at the University of Michigan, Ann Arbor. The students are primarily from mechanical engineering disciplines, but students with a suitable background from other engineering disciplines also are included, as well as practicing engineers in the automotive industry who take the course through distance-learning programs and short courses. We sincerely thank all of our former students for their useful feedback, which led to many improvements in and additions to this material. We also welcome your comments so that we can continue to improve future versions. The current textbook was rewritten extensively from those course notes in collaboration with Melih C¸akmakcı, who was not only a former student who took the course but also has worked in the automotive industry as a control engineer for a decade. He brings an additional perspective to the material from his extensive industrial experience. A. Galip Ulsoy Huei Peng Melih C ¸ akmakcı

PART I

INTRODUCTION AND BACKGROUND

1

Introduction

The century-old automobile – the preferred mode for personal mobility throughout the developed world – is rapidly becoming a complex electromechanical system. Various new electromechanical technologies are being added to automobiles to improve operational safety, reduce congestion and energy consumption, and minimize environmental impact. This chapter introduces these trends and provides a brief overview of the major automobile subsystems and the automotive control systems described in detail in subsequent chapters.

1.1 Motivation, Background, and Overview The main trends in automotive technology, and major automotive subsystems, are briefly reviewed. Trends in Automotive Control Systems The most noteworthy trend in the development of modern automobiles in recent decades is their rapid transformation into complex electromechanical systems. Current vehicles often include many new features that were not widely available a few decades ago. Examples include hybrid powertrains, electronic engine and transmission controls, cruise control, antilock brakes, differential braking, and active/semiactive suspensions. Many of these functions have been achieved using only mechanical devices. The major advantages of electromechanical (or mechatronic) devices, as opposed to their purely mechanical counterparts, include (1) the ability to embed knowledge about the system behavior into the system design, (2) the flexibility inherent in those systems to trade off among different goals, and (3) the potential to coordinate the functioning of subsystems. Knowledge about system behavior – in terms of vehicle, engine, or even driver dynamic models or constraints on physical variables – is included in the design of electromechanical systems. Flexibility enables adaptation to the environment, thereby providing more reliable performance in a wide variety of conditions. In addition, reprogrammability implies lower cost through exchanged and reused parts. Sharing of information makes it possible to integrate subsystems and obtain superior performance and functionality, which are not possible with uncoordinated systems. 3

4

Introduction

Today’s electrical and electronic devices have evolved into systems with good reliability and relatively low cost. They feature many new benefits including increased safety, reduced congestion and emissions, improved gas mileage, better drivability, and greater driver satisfaction and passenger comfort. Safety is perhaps the most important motivation for the increased use of electronics in automobiles. On average, one person dies every minute somewhere in the world due to a car crash. The cost of crashes totals 3 percent of the world’s gross domestic product (GDP) and was nearly $1 trillion in 2000. Clearly, the emotional toll of accidents and fatalities is immeasurable (Jones 2002). Data from the National Highway Transportation Safety Association (NHTSA) show that 6,335,000 accidents (with 37,081 fatalities) occurred on U.S. highways in 1998 (NHTSA 1999). In 2008, the same statistic improved by about 10 percent to 5,811,000 accidents (with 34,017 fatalities) (NHTSA 2009). Data also indicate that although various factors contribute to accidents, human error accounts for 90 percent of all accidents (Hedrick et al. 1994). Delays due to congestion are a major problem in metropolitan areas, providing strong motivation for an increase in automotive electronics. Traffic-information systems can reduce delays significantly by alerting drivers to accidents, congested areas, and alternate routes. Automated highway systems (AHS) at on ramps and tollbooths also can improve traffic flows. Significantly higher traffic flows can be achieved by closely packing automatically controlled vehicles in “platoons” on special highway lanes. These AHS concepts, developed and demonstrated in California, require automatic longitudinal and lateral control of vehicles (Rajamani et al. 2000). In 1970, only 30 million vehicles were produced and 246 million vehicles were registered worldwide; by 1997, these numbers had increased to 56 million and 709 million, respectively. By 2005, 65 million vehicles were produced and more than 800 million were registered (Powers and Nicastri 2000). Consequently, another major factor that contributes to the increased use of electronics is the expanding government regulation of automotive emissions. For example, the 2005 standard for hydrocarbon (HC) emissions was less than 2 percent of the 1970 allowance; for carbon monoxide (CO), it was 10 percent of the 1970 level; and for oxides of nitrogen (NOx ), it was 7 percent of the 1970 level. The California requirements for ultra-low emission vehicles (ULEV) reduced the levels approximately by half again. Spilling 5.7 liters of gasoline on a driveway produces as many HC emissions as a ULEV vehicle driven more than 160,000 kilometers. At the same time, government regulations also require improved fuel economy. Advanced control technologies (e.g., fuel injection, air–fuel ratio control, spark-timing control, exhaust-gas recirculation [EGR], and idle-speed control) are and will continue to be instrumental in reducing emissions and improving fuel economy (e.g., hybrid-electric, all-electric, and fuel-cell vehicles). This evolution (some might say “revolution”) of automotive electronics also is enabled by recent advances in relevant technologies, including solid-state electronics, computer technology, and control theory. Table 1.1 summarizes developments in automotive electronics from 1965 through 2010. The already-evident trend toward increased automotive electronics can be expected to continue in the foreseeable future (Cook et al. 2007; Ford 1986; Powers and Nicastri 2000). In the next decade, significant advances are expected in the use of power electronics, advanced control systems, and alternative powertrain concepts. Among others, new technologies are

1.1 Motivation, Background, and Overview Table 1.1. Historical development of automotive electronics Year

Examples of automotive electronics available

1965

Solid-state radio, alternator rectifier

1970

Speed control

1975

Electronic ignition, digital clock

1980

Electronic voltage regulator, electronic engine controller, electronic instrument cluster, electronic fuel injection

1985

Clock integrated with radio, audio graphic equalizer, electronic air suspension

1990

Antilock brakes, integrated engine and speed control, cellular phones, power doors and windows

1995

Navigation systems, advanced entertainment/information systems, active suspensions

2000

Collision avoidance, autonomous cruise control, vehicle stability enhancement, CVT

2005

Hybrid electric vehicles, driver monitoring, drive-by-wire, integrated vehicle controls

2010

Driver-assist systems (e.g., automated parallel parking), integrated telematics (i.e., location-aware vehicles via mobile devices), plug-in hybrid electric vehicles

being developed for fuel-efficiency management, integrated chassis control, power management of hybrid vehicles, electrical power steering, collision warning and prevention, automatic lane following, rollover and lane-departure warnings, and fuel-cell vehicles. In the near future, it is anticipated that these advancements may reach beyond individual vehicles and eventually lead to the development of Intelligent Transportation Systems (ITS) (Jurgen 1995). Due to rapidly increasing highway congestion, it is necessary for automotive and transportation engineers to devise ways to increase safety and throughput on existing highways. The term ITS (previously referred to as Intelligent Vehicle/Highway Systems [IVHS]) defines a collection of concepts, devices, and services to combine control, sensing, and communication technologies to improve the safety, mobility, efficiency, and environmental impacts of vehicle and highway systems. The importance of ITS is in its potential to produce a paradigm shift in transportation – that is, away from individual vehicles and roadways and toward the development of those that can cooperate effectively, efficiently, and intelligently. Major Automobile Subsystems To provide background for subsequent chapters, this section is an introductory overview of an automobile and its major subsystems. Refer to other sources, including Bastow et al. (2004), Bosch (2009), Dixon (1992), Ellis (1969), Gillespie (1992), Mizutani (1992), Ribbens (2003), Segel (1986), Washine (1989) and Wong (2008), for more in-depth discussions. The functional systems of an automobile are shown in Figure 1.1 and are classified as follows: Chassis or Body. This basic structure of an automobile supports many other systems described herein, as well as passengers and loads. It is supported by the suspension, which connects it to the axles and the wheels. The design of the chassis also affects vehicle dynamics, aerodynamic drag, fuel efficiency, and passenger comfort. The current trend is toward lighter body structures, including

5

This engineering textbook is designed to introduce advanced control systems for vehicles, including advanced automotive concepts and the next generation of vehicles for Intelligent Transportation Systems (ITS). For each automotive-control problem considered, the authors emphasize the physics and underlying principles behind the control-system concept and design. This is an exciting and rapidly developing field for which many articles and reports exist but no modern unifying text. An extensive list of references is provided at the end of each chapter for all topics covered. This is currently the only textbook, including problems and examples, that covers and integrates the topics of automotive powertrain control, vehicle control, and ITS. The emphasis is on fundamental concepts and methods for automotive control systems rather than the rapidly changing specific technologies. Many of the text examples, as well as the end-of-chapter problems, require the use of MATLAB and/or Simulink. A. Galip Ulsoy is the C. D. Mote Jr. Distinguished University Professor and the William Clay Ford Professor of Manufacturing at the University of Michigan. He served as director of the Ground Robotics Reliability Center and deputy director of the Engineering Research Center for Reconfigurable Manufacturing Systems. He has been on the faculty of the Department of Mechanical Engineering at Michigan since 1980 and was the founding director of the Program in Manufacturing. He served as technical editor of the American Society of Mechanical Engineers’ (ASME) Journal of Dynamic Systems, Measurement, and Control and is the founding technical editor of the ASME Dynamic Systems and Control Magazine. Professor Ulsoy is a member of the National Academy of Engineering and a Fellow of the ASME, the International Federation of Automatic Control, and the Society of Manufacturing Engineers; a Senior Member of IEEE; and a member of several other professional and honorary organizations. He is the past president of the American Automatic Control Council. He co-authored, with Warren R. DeVries, Microcomputer Applications in Manufacturing, and he is a co-author, with Sun Yi and Patrick W. Nelson, of Time Delay Systems. He has published more than 300 refereed technical articles in journals, conferences, and books. Huei Peng is a Professor in the Department of Mechanical Engineering at the University of Michigan. He served as the executive director of interdisciplinary and professional engineering programs. His research interests include vehicle dynamics and control, electromechanical systems, optimal control, human-driver modeling, vehicle active-safety systems, control of hybrid and fuel-cell vehicles, energy-system design, and control for mobile robots. He has received numerous awards and honors, including the Chang-Jiang Scholar Award, Tsinghua University; a 2008 Fellow of the ASME; the Outstanding Achievement Award, Mechanical Engineering Department, University of Michigan (2005); the Best Paper Award, 7th International Symposium on Advanced Vehicle Control (2004); and the CAREER Award, National Science Foundation (July 1998–June 2002). He has published more than 200 refereed technical articles in journals, conferences, and books. Professor Peng is co-editor of Advanced Automotive Technologies with J. S. Freeman and co-author of Control of Fuel Cell Power Systems – Principles, Modeling, Analysis and Feedback Design, with Jay T. Pukrushpan and Anna G. Stefanopoulou. Melih Çakmakcı is a Professor of Mechanical Engineering at Bilkent University in Ankara, Turkey. His research areas include modeling, analysis and control of dynamic systems, control systems, smart mechatronics, modeling of manufacturing systems and their control, automotive control systems, optimal energy-management algorithms, and design and analysis of network control systems. Prior to joining Bilkent University, he was a senior engineer at the Ford Scientific Research Center.

Cover photos (insets): Two vehicles negotiating a sharp turn. Blue vehicle is equipped with vehicle stability control, while the red vehicle is not. Courtesy of Ford Motor Company. Cover image: Schematic of two vehicles negotiating a sharp turn. Blue vehicle is equipped with vehicle stability control, while the red vehicle is not. Yellow indicates differential braking used to generate a corrective yaw moment. Courtesy of Ford Motor Company. Cover design by Alice Soloway