Handbook of Compliant Mechanisms

ISBN-13: 9781119953456 / Angielski / Twarda / 2013 / 344 str.

Larry L Howell

Opis

A fully illustrated reference book giving an easy-to-understand introduction to compliant mechanisms A broad compilation of compliant mechanisms to give inspiration and guidance to those interested in using compliant mechanisms in their designs, the Handbook of Compliant Mechanisms includes graphics and descriptions of many compliant mechanisms. It comprises an extensive categorization of devices that can be used to help readers identify compliant mechanisms related to their application. It also provides chapters on the basic background in compliant mechanisms, the categories of compliant mechanisms, and an example of how the Compendium can be used to facilitate compliant mechanism design.

• Fully illustrated throughout to be easily understood and accessible at introductory levels
• Covers all aspects pertaining to classification, elements, mechanisms and applications of compliant mechanisms
• Summarizes a vast body of knowledge in easily understood diagrams and explanations
• Helps readers appreciate the advantages that compliant mechanisms have to offer
• Practical approach is ideal for potential practitioners who would like to realize designs with compliant mechanisms, members and elements
• Breadth of topics covered also makes the book a useful reference for more advanced readers

Intended as an introduction to the area, the Handbook avoids technical jargon to assist non engineers involved in product design, inventors and engineers in finding clever solutions to problems of design and function.

Spis treści

List of Contributors xi

Acknowledgments xv

Preface xvii

PART ONE INTRODUCTION TO COMPLIANT MECHANISMS

1 Introduction to Compliant Mechanisms 3

1.1 What are Compliant Mechanisms? 3

1.2 What are the Advantages of Compliant Mechanisms? 6

1.3 What Challenges do Compliant Mechanisms Introduce? 6

1.4 Why are Compliant Mechanisms Becoming More Common? 7

1.5 What are the Fundamental Concepts that Help Us Understand Compliance? 8

1.5.1 Stiffness and Strength are NOT the Same Thing 8

1.5.2 It is Possible for Something to be Flexible AND Strong 8

1.5.3 The Basics of Creating Flexibility 10

1.6 Conclusion 13

References 13

2 Using the Handbook to Design Devices 15

2.1 Handbook Outline 16

2.2 Considerations in Designing Compliant Mechanisms 16

2.3 Locating Ideas and Concepts in the Library 19

2.4 Modeling Compliant Mechanisms 20

2.5 Synthesizing Your Own Compliant Mechanisms 21

2.6 Summary of Design Approaches for Compliant Mechanisms 22

PART TWO MODELING OF COMPLIANT MECHANISMS

3 Analysis of Flexure Mechanisms in the Intermediate Displacement Range 29

3.1 Introduction 29

3.2 Modeling Geometric Nonlinearities in Beam Flexures 31

3.3 Beam Constraint Model 34

3.4 Case Study: Parallelogram Flexure Mechanism 38

3.5 Conclusions 41

Further Reading 42

4 Modeling of Large Deflection Members 45

4.1 Introduction 45

4.2 Equations of Bending for Large Deflections 46

4.3 Solving the Nonlinear Equations of Bending 47

4.4 Examples 48

4.4.1 Fixed–Pinned Beam 48

4.4.2 Fixed–Guided Beam (Bistable Mechanism) 49

4.5 Conclusions 52

Further Reading 53

References 53

5 Using Pseudo–Rigid Body Models 55

5.1 Introduction 55

5.2 Pseudo–Rigid–Body Models for Planar Beams 57

5.3 Using Pseudo–Rigid–Body Models: A Switch Mechanism Case–Study 60

5.4 Conclusions 65

Acknowledgments 65

References 65

Appendix: Pseudo–Rigid–Body Examples (by Larry L. Howell) 66

A.1.1 Small–Length Flexural Pivot 66

A.1.2 Vertical Force at the Free End of a Cantilever Beam 67

A.1.3 Cantilever Beam with a Force at the Free End 67

A.1.4 Fixed–Guided Beam 69

A.1.5 Cantilever Beam with an Applied Moment at the Free End 70

A.1.6 Initially Curved Cantilever Beam 70

A.1.7 Pinned–Pinned Segments 71

A.1.8 Combined Force–Moment End Loading 73

A.1.9 Combined Force–Moment End Loads 3R Model 74

A.1.10 Cross–Axis Flexural Pivot 74

A.1.11 Cartwheel Flexure 76

References 76

PART THREE SYNTHESIS OF COMPLIANT MECHANISMS

6 Synthesis through Freedom and Constraint Topologies 79

6.1 Introduction 79

6.2 Fundamental Principles 82

6.2.1 Modeling Motions using Screw Theory 82

6.2.2 Modeling Constraints using Screw Theory 84

6.2.3 Comprehensive Library of Freedom and Constraint Spaces 86

6.2.4 Kinematic Equivalence 86

6.3 FACT Synthesis Process and Case Studies 87

6.3.1 Flexure–Based Ball Joint Probe 87

6.3.2 X–Y–ThetaZ Nanopositioner 88

6.4 Current and Future Extensions of FACT s Capabilities 89

Acknowledgments 90

References 90

7 Synthesis through Topology Optimization 93

7.1 What is Topology Optimization? 93

7.2 Topology Optimization of Compliant Mechanisms 95

7.3 Ground Structure Approach 98

7.4 Continuum Approach 100

7.4.1 SIMP Method 100

7.4.2 Homogenization Method 103

7.5 Discussion 104

7.6 Optimization Solution Algorithms 105

Acknowledgment 106

References 106

8 Synthesis through Rigid–Body Replacement 109

8.1 Definitions, Motivation, and Limitations 109

8.2 Procedures for Rigid–Body Replacement 111

8.2.1 Starting with a Rigid–Body Mechanism 111

8.2.2 Starting with a Desired Task 114

8.2.3 Starting with a Compliant Mechanism Concept 115

8.2.4 How DoWe Choose the Best Configurations Considering Loads, Strains, and Kinematics? 116

8.3 Simple Bicycle Derailleur Example 116

References 121

9 Synthesis through Use of Building Blocks 123

9.1 Introduction 123

9.2 General Building–Block Synthesis Approach 123

9.3 Fundamental Building Blocks 124

9.3.1 Compliant Dyad 124

9.3.2 Compliant 4–Bar 125

9.4 Elastokinematic Representations to Model Functional Behavior 125

9.4.1 Compliance Ellipses and Instant Centers 126

9.4.2 Compliance Ellipsoids 127

9.4.3 Eigentwist and Eigenwrench Characterization 130

9.5 Decomposition Methods and Design Examples 134

9.5.1 Single–Point Mechanisms 135

9.5.2 Multi–Port Mechanisms using Compliance Ellipsoids 139

9.5.3 Displacement Amplifying Mechanisms using Instant Centers 143

9.6 Conclusions 145

Further Reading 145

References 146

PART FOUR LIBRARY OF COMPLIANT MECHANISMS

10 Library Organization 149

10.1 Introduction 149

10.1.1 Categorization 149

10.2 Library of Compliant Designs 151

10.3 Conclusion 153

References 153

11 Elements of Mechanisms 155

11.1 Flexible Elements 155

11.1.1 Beams 155

11.1.2 Revolute 161

11.1.3 Translate 179

11.1.4 Universal 181

11.2 Rigid–Link Joints 186

11.2.1 Revolute 186

11.2.2 Prismatic 187

11.2.3 Universal 188

11.2.4 Others 189

References 191

12 Mechanisms 193

12.1 Basic Mechanisms 193

12.1.1 Four–Bar Mechanism 193

12.1.2 Six–Bar Mechanism 195

12.2 Kinematics 197

12.2.1 Translational 197

12.2.2 Rotational 204

12.2.3 Translation Rotation 209

12.2.4 Parallel Motion 214

12.2.5 Straight Line 218

12.2.6 Unique Motion Path 220

12.2.7 Stroke Amplification 227

12.2.8 Spatial Positioning 230

12.2.9 Metamorphic 233

12.2.10 Ratchet 237

12.2.11 Latch 241

12.2.12 Others 243

12.3 Kinetics 245

12.3.1 Energy Storage 245

12.3.2 Stability 252

12.3.3 Constant Force 262

12.3.4 Force Amplification 263

12.3.5 Dampening 267

12.3.6 Mode 268

12.3.7 Others 269

References 272

13 Example Application 277

13.1 Elements of Mechanisms: Flexible Elements 277

13.2 Mechanisms: Kinematic 282

13.3 Mechanisms: Kinetic 291

References 317

Index 319

O autorze

Larry L. Howell is Chair of the Mechanical Engineering Department at Brigham Young University in Provo, Utah.

Blurb

Provides guidance and inspiration for developing compliant mechanisms

Compliant mechanisms offer advantages such as increased performance (for example, high precision, low weight, low friction), lower cost (such as simplified manufacture, low part count), and ability to miniaturize (they make possible micro and nano mechanical devices). However, because compliant mechanisms are relatively new compared to more traditional devices, it is difficult to find examples and resources to guide them device designers in their work.

The Handbook of Compliant Mechanisms provides a resource to those interested in exploiting the unique advantages of compliant mechanisms. It includes a concise summary of modelling and design methods, plus a broad compilation of compliant mechanisms that will provide inspiration and guidance for new designs. Other chapters provide basic background in compliant mechanisms, summaries of the major methods for their modelling and design, and an example of how the Handbook can be used to facilitate compliant mechanism design.

Key features:

• Fully illustrated throughout to be easily understood and accessible at introductory levels, whilst the breadth of topics makes the book a useful reference for more advanced readers
• Helps readers appreciate the advantages that compliant mechanisms have to offer
• Covers all aspects pertaining to classification, elements, mechanisms and applications of compliant mechanisms