Linear Engine / thesis

The Dynamic Design Lab has hosted me for nearly four years now, and interacting with its members has been one of the most rewarding parts of my research experience. Many of my problems were solved by my peers, who always seemed to have time to listen. Most important of these were Eric Rossetter, who was good enough to inadvisably trust me with his life while driving down Page Mill Road, and Chris Carlson, who even put up with living with me. Other important sounding boards and compatriots were Greg Shaver, Matt Schwall, Sam Chang, Jihan Ryu, and Paul Yih. Hong Bae deserves my particular thanks for educating me about the process of writing an Engineer’s Thesis. Special recognition goes to Doug Bourne, who during summer of 2001, worked with me on this project. His contribution is di cult to overestimate, both in terms of his actual work output and as a sounding board.

No one was more instrumental in this process than my advisor, Prof. Chris Gerdes. During my time at Stanford I was pleased to work with him as he made the transition from industry wizened newcomer to a professor emblematic of Frederick Terman’s idea of a “steeple of excellence”. He was resourceful and supportive in coming up with funding for this research, and patiently guided the process through many apparent dead ends. I’ve learned a great deal about engineering from him, and he helped me to learn much about myself.

Finally, I must thank my family. My brothers, Paul and Tom, have always been my best friends, and help me to keep things in perspective. My father, Ronald, is my most important role model as an engineer and as a good sport. My mother, Diana, taught me most of what I know about being a decent person. This thesis is devoted to them.

xi

Contents

2.1Benchmarking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.1.1West Virginia University . . . . . . . . . . . . . . . . . . . . . 12

2.1.2Sandia National Labs . . . . . . . . . . . . . . . . . . . . . . . 13

xiii

2.2.2Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.2.3 Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.1Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.1.1Thermodynamic System . . . . . . . . . . . . . . . . . . . . . 22

3.1.4Initial Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.2Electrical Machine Selection . . . . . . . . . . . . . . . . . . . . . . . 33

3.2.1Motor vs. Generator . . . . . . . . . . . . . . . . . . . . . . . 35

3.2.2Brush vs. Brushless . . . . . . . . . . . . . . . . . . . . . . . . 36

3.2.5Linear vs. Rotary . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.2.6The Aerotech BLMX-502B . . . . . . . . . . . . . . . . . . . . 38

3.3.1Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

3.3.3 Integrating the Electronic System . . . . . . . . . . . . . . . . 56

3.4Experimental Determination of Motor Constant . . . . . . . . . . . . 57

3.4.1 Applying a Known Constant Force . . . . . . . . . . . . . . . 59

3.4.2Measuring the Current . . . . . . . . . . . . . . . . . . . . . . 60

3.4.5Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

xiv

4.1Linear Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

4.2Energy Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

4.3Dynamic Cabling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

5.2Mechanical Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . 89

5.3Electrical Subsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

5.4Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

xv

List of Tables

2.1 Summary of Benchmark Linear Engine Parameters . . . . . . . . . . 12

3.1Notations for Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.2 Engine Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.3Comparison Between DC and AC Motors . . . . . . . . . . . . . . . . 37

3.4Comparison Between Linear and Rotary Motors . . . . . . . . . . . . 38

3.5Cost Comparison by Quantity of Linear Motors . . . . . . . . . . . . 39

3.6Key Motor System Parameters . . . . . . . . . . . . . . . . . . . . . . 41

4.1Failure Modes Necessitating Shock Absorber . . . . . . . . . . . . . . 77

xvii

List of Figures

2.1Schematic of Variable Valve Actuation System (taken from [14] with

2.2Optical Cylinder Interface . . . . . . . . . . . . . . . . . . . . . . . . 20

3.1Wire in a Magnetic Field . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.2Solenoid . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

3.5PV Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

3.6Position and Force vs. Time . . . . . . . . . . . . . . . . . . . . . . . 34

3.7BLMX-502b Coil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.8MTX-720 Magnet Way . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.9BAS-100 Sinusoidal Amplifier . . . . . . . . . . . . . . . . . . . . . . 40

3.10Mechanical and Electrical Data for Closed Loop Simulation . . . . . . 43

3.11PV Diagram for Closed Loop Simulation . . . . . . . . . . . . . . . . 44

3.12Mechanical and Electrical Data for Variable Rate Simulation . . . . . 45

xix

3.19Top Portion of Prototype, Inverted . . . . . . . . . . . . . . . . . . . 53

3.20End View of Complete Prototype . . . . . . . . . . . . . . . . . . . . 54

3.25Static Friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

3.26Current Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

3.27Current vs. Position, 50 lbs. . . . . . . . . . . . . . . . . . . . . . . . 62

3.28Current vs. Position, 100 lbs. . . . . . . . . . . . . . . . . . . . . . . 63

3.29Current vs. Position, 150 lbs. . . . . . . . . . . . . . . . . . . . . . . 64

4.1Schematic CAD Model of Igus Bearing . . . . . . . . . . . . . . . . . 71

4.2Photograph of Igus bearing in Prototype . . . . . . . . . . . . . . . . 71

4.3Ceramic Bearing and Pillow Block . . . . . . . . . . . . . . . . . . . . 73

4.4End View of Ceramic Bearing and Pillow Block on Shaft . . . . . . . 74

4.5Assembly of Bearings on Shaft . . . . . . . . . . . . . . . . . . . . . . 74

4.6Aluminum Honeycomb Material . . . . . . . . . . . . . . . . . . . . . 76

xx