SAE R-217-2000 Fundamentals of Crash Sensing in Automotive Air Bag Systems (To Purchase Call 1-800-854-7179 USA Canada or 303-397-7956 Worldwide).pdf

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1、Fundamentals of Crash Sensing in Automotive Air Bag Systems Ching-Yao ChanFundamentals of Crash Sensing in Automotive Air Bag Systems Ching-Yao Chan Society of Automotive Engineers, Inc. Warrendale, Pa. Copyright 2000 Society of Automotive Engineers, Inc. eISBN: 978-0-7680-6378-3Library of Congress

2、Cataloging-in-Publication Data Chan, Ching-Yao. Fundamentals of crash sensing in automotive air bag systems / Ching-Yao Chan. p. cm. Includes bibliographical references and index. ISBN 0-7680-0499-3 1. Air bag restraint systems. 2. Crash sensors. 3. Automo- tive sensors. I. Title TL159.5.C47 2000 62

3、9.276-dc21 99-045839 CIP Copyright 2000 Society of Automotive Engineers, Inc. 400 Commonwealth Drive Warrendale, PA 15096-0001 U.S.A. Phone: (724)776-4841 Fax: (724)776-5760 E-mail: publicationssae.org http:/www.sae.org ISBN 0-7680-0499-3 All rights reserved. Printed in the United States of America

4、Permission to photocopy for internal or personal use, or the internal or personal use of specific clients, is granted by SAE for libraries and other users registered with the Copy- right Clearance Center (CCC), provided that the base fee of $.50 per page is paid directly to CCC, 222 Rosewood Dr., Da

5、nvers, MA 01923. Special requests should be addressed to the SAE Publications Group. 0-7680-0499-3/00-$.50. SAE Order No. R-217 Front cover photo courtesy of Delphi Automotive Systems. Back cover photo courtesy of Motorola.Contents Foreword vii Chapter 1 History and Background 1 1.1 A Historical Per

6、spective 1 1.2 Accident Statistics: Are Air Bags Effective? 4 1.3 How Do Air Bags Work? 7 1.4 Design Issues and Considerations. 10 1.5 Recent Developments 11 1.6 Summary 12 Exercises 13 References 13 Chapter 2 Crash Analysis 15 2.1 Crash Data 15 2.2 Crash Analysis: What Information Can Be Extracted

7、from Crash Data? 18 2.3 Crash Data Examples 22 2.4 Observations and Discussions about Crash Data 26 2.5 Crash Library for Sensor Design 34 2.6 Summary 34 References 35 Chapter 3 Crash Sensing Criteria 37 3.1 Threshold of Collision Severity: When is an Air Bag Deployment Needed? 37 3.2 Rule of 5 Inch

8、es Minus 30 Milliseconds and Sensor Triggering Time 39 3.3 Occupant Performance Criterion 42 iiiFundamentals of Crash Sensing in Automotive Air Bag Systems 3.4 Crash Sensing Characteristics 48 3.5 Summary 50 References 50 Chapter 4 Crash Sensing Concepts 53 4.1 Signals for Crash Detection 53 4.2 Spe

9、ed-Dependent Crash Sensing 56 4.3 Crush-Dependent Crash Sensing 59 4.4 Electronic Sensors 61 4.5 Other Sensor Concepts and Systems 64 4.6 Summary 65 References 65 Chapter 5 Mechanical Crash Sensors 67 5.1 Exemplar Crash Sensors 67 5.2 Mathematical Analysis of Mechanical Crash Sensors 73 5.3 Sensor S

10、ensitivity and Characteristics 80 5.4 Sensor Testing 84 5.5 Summary 86 References. 87 Chapter 6 Electronic Crash Sensors 89 6.1 What Are Electronic Crash Sensors and Why Are They Used? 89 6.2 Functions and Components of Electronic Crash Sensors91 6.3 Sensing Algorithms in Electronic Sensors 95 6.4 S

11、ignals and Variables in Sensing Algorithms 111 6.5 Summary 112 References 113 Chapter 7 Crash Sensor Placement Strategies 117 7.1 Distributed Sensing and Single-Point Sensing 118 7.2 All-Mechanical Air Bag Systems 121 7.3 Single-Point Sensing Concept and Electronic Sensors123 7.4 Summary 128 Exercis

12、es 129 References 129 ivContents Chapter 8 Side Impact Sensing and Air Bags 131 8.1 Side Impact 131 8.2 Kinematic Analysis of Side Impact 133 8.3 Sensing Concepts and Examples 137 8.4 Summary 147 References. 147 Chapter 9 Transitions and Trends in Crash Sensing Technologies and Automotive Restraint

13、Systems 151 9.1 Definition of a Smart Air Bag System 152 9.2 Elements of Smart Air Bags 156 9.3 Integrated Sensing System 160 9.4 A Perspective of Complete Restraint System Design 162 9.5 Summary 164 Exercises 165 References 165 Glossary 169 Bibliography 173 Index 185 About the Author 197 vForeword

14、This book has been written to address the needs of several groups of people: The first group consists of those who have not previously worked with air bag sensors or restraint systems. This includes engineers who have just started in the practice of designing crash sensors; accident reconstructionis

15、ts who would like to learn about vehicular safety systems; litigators who want to further their knowledge about such systems; and anyone else with a personal or professional interest in learning about the subject. In the second group are those who have worked in this field briefly or tangen- tially,

16、 but would benefit from a systematic reference covering the essential elements of the subject. A third group consists of persons in managerial positions or supervisory roles who require an overview of air bag sensors or restraint systems. When I first started working in this field, in 1988, I belong

17、ed to the first group described above. The air bag industry was just beginning to take off at that time, and research and development in the area was proceeding at a rapid rate. Although basic knowledge and expertise about air bags was well established, it was difficult for a newcomer to grasp it. T

18、he problem was that the leaders in the fieldthose with the most extensive technical backgrounds and understanding were too busy with day-to-day practical concerns to take time out to teach or write on the subject. I remember what a struggle it was for me to acquire pieces of knowledge about air bags

19、 and sensors in the absence of a good reference book on the subject. I hope this book will help readers who find themselves in the same situation I was in. viiFundamentals of Crash Sensing in Automotive Air Bag Systems What can one expect from this book? This book provides a systematic description o

20、f the essential techniques and pro- cedures used in the design of crash sensors. Its aim is to give readers an overall picture of how and why crash sensors in air bag systems work, and why in certain situations they do not work properly. Sophisticated equations are purposely absent from the book, al

21、though an under- standing of fundamental physics and mathematics may be required to read cer- tain sections. Tables or guidelines for selecting parts or materials for product development purposes have also been omitted, as these are considered too prod- uct-specific for a book of this nature. What i

22、s in this book? This book draws on the wisdom and opinions of many pioneers and knowledge- able individuals who have worked with air bag sensors and restraint systems. Since the field originated many years ago, long before I became involved, Ive found it necessary to cite prior art in order to help

23、formulate my own interpreta- tion. If Ive made any errors in discussing the work of others, I take full respon- sibility for any misrepresentation. This book contains nine chapters, which can be read sequentially or selectively. In Chapter 1, history, accident statistics and design issues are cited

24、to give the reader a background of the subject. In Chapter 2, the reader is introduced to the terminology and techniques of crash data analysis that are used throughout the book. Chapter 3 covers the procedure for determining the timing of sensor response. Chapter 4 introduces the basic concepts and

25、 types of crash sensors. Chapter 5 dissects the underlying principles and phenomena of mechanical sensors. viiiForeword Chapter 6 details the elements and sensing algorithms of electronic sensors. Chapter 7 discusses the strategies for placing crash sensors on a vehicle. Chapter 8 is devoted to side

26、 impact air bags and the associated sensor design problems. Chapter 9 explores the meaning of “smart“ air bag systems, which represent the upcoming generation of products, aimed at resolving certain shortcom- ings of current systems. The chapter concludes with some thoughts on future advancements in

27、 restraint technologies. How to read this book Since the book is intended for a wide range of readers, its is structured so that readers may choose to skip some sections. I offer the following suggestions: For a quick overview of crash sensing technologies, read Chapter 1 and the first halves of Cha

28、pters 5 and 6, and then Chapters 7, 8, and 9. This shortcut will provide a review of the history of sensing technologies and system intro- duction, principles and examples of existing sensors, placement of sensors, and the latest developments in sensing technologies. If you are just beginning to wor

29、k in the field, read Chapters 2, 3, and 4. After a study or review of these sections, you should have a solid understanding of the terminology and skills used by people in the field. For further explora- tion, read the second halves of Chapters 5 and 6, where specific design prin- ciples are discuss

30、ed. Those readers interested in the state of research and development of future safety systems will find discussions of specific topics in Chapter 9. In a fast- changing industry, research and development topics evolve continuously and current technology becomes obsolete rather quickly. Consequently

31、, the opin- ions and interpretation offered in this chapter should be viewed as a starting point, but not as the final word. As a “first“ book on the subject, this work focuses on fundamentals and pur- posely omits more complex aspects of air bag sensor design. In this sense it is ixFundamentals of

32、Crash Sensing in Automotive Air Bag Systems incomplete because there is a vast pool of knowledge and an extensive list of additional topics that could have been included. Interested readers are strongly encouraged to expand and update their knowledge by consulting both the cited references and curre

33、nt and future publications in the field. Ching-Yao Chan xChapter 1 History and Background This chapter provides a brief review of the history of automotive safety systems, particularly the growth of air bag technology from the late 1980s to the mid- 1990s. Also reviewed are statistics collected in r

34、ecent years about air bag ben- efits and problems. The functioning sequence of air bag restraint systems, especially the criticality of crash sensing devices, is also discussed. The chapter concludes with an overview of considerations and issues involved in the design of air bag systems. 1.1 A Histo

35、rical Perspective The evolution of vehicular safety and occupant restraint systems in the U.S. auto- motive industry progressed significantly in the 1980s and 1990s. However, a glance at Table 1.1, which lists selected milestones in the history of automotive safety systems, reveals that the developm

36、ent of safety devices from a prototype stage to that of a commonly accepted commercial product has taken a consider- able amount of time. 1.1.1 Selected Milestones in the History of Automotive Safety Systems Table 1.1 Selected milestones in automobile safety history 1 1Fundamentals of Crash Sensing

37、in Automotive Air Bag Systems Table 1.1 Selected milestones in automobile safety history 1 (cont.) 1.1.2 Selected Milestones in the Development of Automotive Air Bag Systems The first U.S. patent on an air bag system was issued to J.W. Hetrick on August 18, 1953 2. It is noteworthy that the inventio

38、n detailed in the patent contained many of the features still considered essential in many air bag products 30 years later. In particular, the crash sensor concept outlined in Hetricks patent is simi- lar in principle to certain types of sensors used on vehicles today. Table 1.2 lists major mileston

39、es in the implementation of air bag standards over the last three decades 3. 2History and Background Table 1.2 History of air bag standards 3 3Fundamentals of Crash Sensing in Automotive Air Bag Systems 1.1.3 Growing Presence of Air Bags A variety of forces converging in the 1980s finally brought ab

40、out the widespread installation and use of air bags in U.S. passenger vehicles. These forces included: (a) Government regulation The revision and enactment of federal regulations on passive restraint systems propelled automobile manufacturers and their suppliers to standardize and mass- produce air

41、bags. (b) Readiness and affordability of technologies A number of suppliers were ready to roll out products. Although the prices of these first air bags were initially high compared to today, they were at a level acceptable both to the automobile makers and to the public. (c) Consciousness about veh

42、icular safety By the late 1980s, a gradual shift in societys consciousness of vehicle safety culminated in the introduction of air bags. Educational and promotional efforts by various institutions and advocacy groups had already led to the enforcement of safety belt laws in many states; the installa

43、tion of air bags was the logical “next step.“ Subsequently, for a period of several years, most automobile manu- facturers used safety as the primary selling point in their advertisements and television commercials. (d) Cost reduction and mass production As air bag systems increasingly became standa

44、rd in new light-duty vehicles, the number of units produced soared. Fierce competition put enormous pressure on suppliers to reduce costs and unit prices. This economic factor, together with the other forces mentioned above, accelerated factory installation of one or more air bags in virtually all O

45、EM light vehicles sold in the U.S. today. 1.2 Accident Statistics: Are Air Bags Effective? In recent years, given the increasing number of vehicles on the road equipped with air bags, there have been ongoing discussions about the effectiveness of these devices. A number of incidents caused by air ba

46、g deployment, which resulted in fatalities and injuries, especially to children, have raised the concerns of the 4History and Background public in recent years. However, despite these concerns, the benefits of reducing fatalities and mitigating injuries are still being realized by standardizing air

47、bag installation. To further understand the reasons and arguments behind the debate regarding air bag benefits, from both sides of the issue, consult the articles sug- gested in the references 4. Based on data presented in a 1994 study 5, 53,717 motor vehicles were involved in 35,747 fatal crashes i

48、n 1993, resulting in 40,115 deaths. Of these fatalities, 22,031 deaths were of occupants of passengers cars and 7,171 of occupants of pickup and utility vehicles. Table 1.3 shows a further breakdown of these num- bers by type of crash and point of principal impact 5. It can be seen from Table 1.3 th

49、at approximately 50% of all fatalities occurred in frontal impacts, thus it is reasonable to pursue the protection of occupants by starting with frontal air bags. Since many fatalities also occur in side impacts, manufacturers have been justified in bringing side protection restraints into the market in recent years once frontal air bags became standard equipment. Table 1.3 Passenger vehicle occupant deaths by crash type and point of principal impact, 1993 With a significant number of air-bag-equipped cars now on the road, meaningful statistics have begun to revea