Compliant Mechanisms

Book Preface

Compliant mechanisms offer great promise in providing new and better solutions to many mechanical-design problems. Since much research in the theory of compliant mechanisms has been done in the last few years, it is important that the abundant information be presented to the engineering community in a concise, understand­able, and useful form. The purpose of this book is to fulfill this need for students, practicing engineers, and researchers.

The book presents methods for the analysis and design of compliant mechanisms and illustrates them with examples. The materials in the book provide ideas for engineers to employ the advantages of compliant mechanisms in ways that otherwise may not be possible. The analysis of small deflection devices is addressed, but emphasis is given to compliant mechanisms that undergo large, nonlinear deflections. The pseudo-rigid-body model is introduced as a method which simplifies the analysis of compliant mechanisms that undergo large deflections by modeling them with elements common to traditional mechanisms. This simplification makes it possible to design compliant mechanisms for many types of tasks. The advantages of compliant mechanisms in the emerging area of microelectromechanical systems (MEMS) are also addressed, and several MEMS examples are provided throughout the book.

The chapters are organized to flow from simple to more complex concepts; the book then concludes with the application of the previous materials to specific types of devices. This is done by organizing the chapters into major sections of introduc­tion, fundamentals, analysis, design, and special-purpose mechanisms. In a similar way, simple examples facilitate understanding, followed by more complicated examples that demonstrate how the material can be used in applications.

Review of essential topics in strength of materials, machine design, and kine­matics is provided to create a self-contained book that does not require a lot of addi­tional references to solve compliant-mechanism problems. These reviews can help emphasize important topics the reader has studied previously, or they can be used as a resource for those from other disciplines who are working in the area of MEMS or related areas. The appendixes provide a resource for quick reference to important equations presented in the book.

The area of compliant mechanisms exists thanks to the vision and insight of Professor Ashok Midha. Many have contributed to the knowledge of compliant mechanisms, but Professor Midha may be considered the father of modern compli­ant mechanisms. His insight and vision have had a profound effect on the field and on those with whom he has associated. I have greatly benefited from both his work in compliant mechanisms and his example and mentorship, and I am grateful for his influence.

The earlier versions of this book were used as notes in compliant mechanisms courses offered at Brigham Young University, Purdue University, and the University of Missouri, Rolla. Students made many helpful comments to improve the quality of the notes.

Several colleagues have graciously volunteered their time and expertise by con­tributing parts of the book. Professor G. K. Ananthasuresh at the University of Pennsylvania and Professor Mary I. Frecker at Pennsylvania State University wrote Chapter 9. Dr. Morgan D. Murphy of Delphi Automotive Systems contributed Appendix G. Chapter 11 relies heavily on graduate work completed by Brian Jensen when he was at Brigham Young University.

Some of the text and figures in this book are summarized from previous writ­ings, including a number of papers coauthored with graduate students and col­leagues and published by the American Society of Mechanical Engineers (ASME) in various conference proceedings and in the Journal of Mechanical Design. Work from a number of graduate student theses has also been included. Grateful thanks is extended to all those who have participated in this work: James Derderian, Patrick Opdahl, Brian Edwards, John Parise, and Brian Jensen have generously contributed sections of this book. The contributions of Scott Lyon, Brent Weight, and Greg Roach are also greatly appreciated, as are the efforts of many other students that have made this possible. The valuable assistance of Megan Poppitz is also grate­fully acknowledged.
The Mechanical Engineering Department at Brigham Young University has been very supportive of this project and has provided many resources to assist in its completion. The College of Engineering and the administration of Brigham Young University have also suppo11ed the author’s efforts in many ways.

In addition to the many students who have provided recommendations and encouragement for this work, others are thanked for their helpful reviews and com­ments to improve the manuscript. Special thanks to Professor G. K. Ananthasuresh, Dr. Morgan D. Murphy, Professor Kenneth W. Chase, and Professor Don Norton of Brigham Young University’s English Department, and the university editing service for valuable reviews and comments on the manuscript.

Much of the fundamental work in compliant mechanisms has been funded by the National Science Foundation (NSF). The resources provided were a wise invest­ment and will have a far-reaching impact for many years to come. The following NSF grants have supported the author’s work in the area of compliant mechanisms: DMI-96245 74 (CAREER Award), CMS- 99 78737, ECS-9 528238, and DMl- 998083 5. The Utah Center of Excellence Program is also acknowledged for support of commercialization of compliant mechanism theory through funding of the Cen­ter of Excellence in Compliant Mechanisms.
I express my love and gratitude to my wife and children for their continued love, support, and companionship. And my eternal thanks to my parents, for their love and sacrifice. Finally, I humbly acknowledge the gifts from God, for which no words could ever adequately express my gratitude.