CRANFIELD UNIVERSITY O PLATTARD BRAKE FEEL: INVESTIGATION OF THE BRAKE DESIGN PARAMETERS’ INFLUENCE SCHOOL OF ENGINEERING MSc THESIS CRANFIELD UNIVERSITY SCHOOL OF ENGINEERING MSc THESIS Academic Year 2005-2006 O PLATTARD BRAKE FEEL : INVESTIGATION OF THE BRAKE DESIGN PARAMETERS’ INFLUENCE Supervisor: J Marco September 2006 This thesis is submitted in partial fulfilment of the requirements for the degree of Master of Science © Cranfield University 2006 All rights reserved No part of this publication may be reproduced without the written permission of the copyright owner Abstract The development of environmental-friendly cars has led car manufacturers to explore new propulsion systems One of them is the Hybrid Electric Vehicle This particular type of vehicle is usually fitted with a regenerative braking system that captures the vehicle kinetic energy lost when braking Therefore a brake emulator has to be implemented instead of the brake pedal to isolate the driver’s brake requirement In doing so, the feedback from the braking system – the brake feel – is lost and needs to be simulated by the brake emulator However up to now very little research has been done on this particular domain which remains relatively unknown The purpose of this thesis is to consequently understand the role each component of a braking system plays in brake feel In order to investigate the influence of the brake design parameters on brake feel a braking system model has been used and run with AMESim Brake feel was assessed using 10 criteria extracted from the curves representing pedal stroke vs applied force and pedal stroke vs vehicle deceleration A range of 13 brake design parameters were then tested and their influence studied The final result is two sets of maps The first one relates a given brake feel criteria to all the design parameters, and the second relates a given design parameter to all the brake feel criteria Furthermore a ratio has been calculated that gives the average influence each parameter has on brake feel and vice-versa These results can then be used to tune a brake emulator according to the brake feel one wants to give to a car One can also predict the brake feel associated with one particular braking system i ii Acknowledgment I would like to make the most of this page to acknowledge the assistance, patience and support of many people during my year at Cranfield University Firstly, I would like to express my deepest gratitude to my supervisor, Dr James Marco, for his continuous guidance and support throughout the length of the project His door has always been open and both his technical advice and friendliness proved to be of great value I would also like to thank Dr Marko Tirovic for having helped me at the early stage of the thesis Thank you to the Application Engineer from Imagine, Emmanuel Domingues, who has given me a lot of time and explanations My thanks go to the entire staff of the MSc in Automotive Product Engineering who have made this year a valuable year A special thanks goes to Catriona Rolfe who has put up with me for one year and whose e-mail will long be missed Special thanks are extended to my classmates who I had the pleasure to meet this year in an international context It has been a very enriching experience A very warm thank you to: Maryneidy Arocha Santiago Marie-Line Guillermin Ramy Karoun Hong Chi Lee Pierre Tipner Finally I would like to thank my parents and my sister for all their support throughout my academic life and especially for this year that has not always been funny iii iv Table of contents Abstract i Acknowledgment iii Table of contents v Table of figures vii Table of acronyms xi Presentation of the thesis .1 1.1 Context 1.2 Subject Literature review 2.1 Electro hydraulic and regenerative braking 2.2 Brake feel 2.3 Braking system model 11 2.4 Conclusions 14 The braking system model 16 3.1 Model requirements .16 3.2 Presentation of AMESim’s model 16 3.2.1 The global model 17 3.2.2 The vacuum booster .18 3.2.3 The master cylinder 20 3.2.4 The calliper 23 3.3 Improvement of the model 24 3.3.1 The Calliper 24 3.3.2 The master cylinder 25 3.3.3 The brake pedal 26 3.3.4 Implementing a fluid reservoir 29 3.3.5 Implementing a vehicle dynamic model 31 3.4 Validation of the model 35 3.5 Final model 37 3.6 Simulation parameters 37 3.7 Baseline results 37 Investigation of the parameters influencing brake feel 42 4.1 Vehicle dynamics’ parameters 42 4.1.1 Number of bores 43 4.1.2 Mean swept radius 44 4.1.3 Friction between pad and disc 46 4.1.4 Vehicle mass 47 4.1.5 Wheel radius 48 4.1.6 Discussion 49 4.2 Calliper’s parameters 50 4.2.1 Gap between pad and disc 50 4.2.2 Front bore’s diameter 52 4.2.3 Rear bore’s diameter 54 4.3 Vacuum booster’s parameters 55 4.3.1 Engine depression 55 4.3.2 Vacuum booster’s reaction disc diameter 58 v 4.4 Master cylinder’s parameters .59 4.4.1 Master cylinder’s diameter 60 4.4.2 Master cylinder’s volume .61 4.4.3 Primary spring 62 4.4.4 Secondary spring 64 4.4.5 Underlap 65 4.5 Pedal’s parameters .66 4.4.2 Pedal length 66 4.4.3 Pedal ratio 68 Results and further work 70 5.1 Presentation of the results 70 5.1.1 Relation brake feel to parameters 70 5.1.2 Relation parameter to brake feel 72 5.2 Further work 75 5.2.1 Useability of AMESim .75 5.2.2 Model enhancement .75 5.2.3 Brake feel assessment 75 5.2.4 Brake emulator development 75 Conclusion 76 References 79 Bibliography .81 Appendices 83 Appendix A: AMESim Final model .84 Appendix B: Summary of the brake design characteristics .86 Appendix B: Influence of mean swept radius 88 Appendix C: Influence of the coefficient of friction between the pad and the disc 89 Appendix D: Influence of the wheel radius 90 Appendix E: Influence of gap between pad and disc 91 Appendix F: Influence of front bore’s diameter .92 Appendix G: Influence of rear bore’s diameter 93 Appendix H: Influence of engine depression 94 Appendix I: Influence of reaction disc diameter .95 Appendix J: Influence of the master cylinder’s diameter 96 Appendix K: Influence of the master cylinder’s volume 97 Appendix L: Influence of the primary spring stiffness 98 Appendix M: Influence of the secondary spring stiffness 99 Appendix N: Influence of the underlap 100 Appendix O: Influence of the pedal length 101 Appendix P: Influence of the brake pedal ratio 102 vi ... regarding the influence of a braking system’s parameters on brake feel The thesis is therefore entitled: investigation of the brake design parameters’ influence on brake feel The following objectives... assess brake feel • Find all the design parameters of a braking system • Model the braking system • Validate the model • Investigate the influence of the design parameters on brake feel The modelling... B: Summary of the brake design characteristics .86 Appendix B: Influence of mean swept radius 88 Appendix C: Influence of the coefficient of friction between the pad and the disc 89