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Theoretical and Experimental Investigations on a New Adaptive Duo Servo Drum Brake with High and Constant Brake Shoe Factor

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Theoretical and Experimental Investigations on a New Adaptive Duo Servo Drum Brake with High and Constant Brake Shoe Factor THEORETICAL AND EXPERIMENTAL INVESTIGATIONS ON A NEW ADAPTIVE DUO SERVO DRUM BRAKE WITH HIGH AND CONSTANT BRAKE SHOE FACTOR Zur Erlangung des akademischen Grades eines DOKTORS DER INGENIEURWISSENSCHAFTEN (Dr.-Ing) von der Fakultät für Maschinenbau der Universität Paderborn genehmigte DISSERTATION von M. Sc. Khaled R. M. Mahmoud aus El-Minia- Ägypten i ACKNOWLEDGEMENTS This dissertation was elaborated during my stay as a member of Egyptian scholarships on the mechatronic and dynamic research group, university of Paderborn, Paderborn, Germany. I would like to thank especially Prof. Dr-Ing. J. Wallaschek for his encouragement and guidance during my Ph. D. studies. He supported me far exceeded my expectations and contributed definitely to the success of this thesis. Also, he helped me to pursue this research. I thank sincerely Prof. Dr-Ing. D. Zimmer, who nicely accepted to write the second expert’s survey. I want to thank sincerely to ass Prof. T. Sattel for his guidance for the theoretical part of the thesis and for his daily conversations and scientific discussions. Special thanks to all members of mechatronic and dynamic research group for their help and assistance. I am particularly grateful to Dr-Ing H. Storck, Dipl-Ing R. Boer, Dipl-Ing M. Liekenbröcker and Dr-Ing T. Hemsel who were right downstairs when I had questions about my theoretical and experimental works. I thank sincerely Prof. Dr-Ing. D. Zimmer and Dipl-Ing H. Kammler for their help and allowance to built my test rig in their laboratory during the experimental part of this study. My wife and my children deserve an award for their patience and supporting during the writing of this thesis. I could not have done it without them. I am grateful for the supporting of my parents over the last decade or so as I finished my studies. Paderborn, July 2005 Khaled Mahmoud Aus dieser Arbeit wurden keine Teile bereits veröffentlicht. Paderborn den 11.04.05 Khaled Mahmoud iii To my wife v Contents 1 Introduction.....................................................................................................1 2 Background on automotive brake systems and state of the art.................3 2.1 Friction brakes ................................................................................................. 3 2.1.1 Disc brake.....................................................................................................5 2.1.2 Drum brakes .................................................................................................6 2.2 Brake-by-wire................................................................................................... 8 2.2.1 Electromechanical brake EMB....................................................................10 2.3 Electro hydraulic brake EHB .......................................................................... 11 2.4 Design considerations for wheel brakes ........................................................ 11 2.4.1 Coefficient of friction ...................................................................................11 2.4.2 General aspects..........................................................................................15 2.4.3 Special requirements for brake-by-wire ......................................................17 2.5 Concepts for self-amplifying wheel brakes..................................................... 19 2.5.1 Literature and patent survey .......................................................................19 2.5.2 Wedge disc brake .......................................................................................20 2.5.3 Drum brakes ...............................................................................................21 3 Problem formulation.....................................................................................23 3.1 Deficits of present day self-amplifying wheel brakes ..................................... 23 3.2 Proposed solution: adaptive self-amplification brake ..................................... 24 3.3 Aim of the study ............................................................................................. 25 4 Analysis of self-amplifying wheel brakes ...................................................27 4.1 Lever brake.................................................................................................... 27 4.2 Wedge brake ................................................................................................. 29 4.3 Drum brakes .................................................................................................. 30 4.3.1 Simplex drum brake....................................................................................30 4.3.2 Duplex drum brake .....................................................................................33 4.3.3 Duo servo drum brake ................................................................................34 4.4 Comparison of the concepts and selection of the most promising solution approach................................................................................................................... 42 5 Design of a prototype of an adaptive duo servo drum brake ...................45 5.1 General concept ............................................................................................ 45 5.2 Control concepts............................................................................................ 47 5.2.1 Brake control system ..................................................................................47 5.2.2 Friction observer .........................................................................................47 5.2.3 Adaptation strategies ..................................................................................48 6 Experimental setup and results...................................................................51 6.1 Description of the test-rig prototype ............................................................... 51 6.2 Description of the test-rig and measurement equipment................................ 52 6.2.1 Applied force generation.............................................................................52 6.2.2 Linear actuator construction........................................................................52 6.2.3 Stroke sensor measurement.......................................................................53 6.2.4 Torque and speed measurements ..............................................................54 6.2.5 Motor and gearbox......................................................................................54 6.2.6 Experimental investigations of the brake system ........................................56 6.3 Experimental results ...................................................................................... 57 6.3.1 Effect of the working parameters ................................................................58 6.3.2 Control of the brake shoe factor..................................................................67 7 Conclusions ..................................................................................................73 8 Summary and outlook ..................................................................................79 References ...............................................................................................................81 vii NOMENCLATURES Symbol unit meaning a m Distance between drum centre point and floating link A N Anchor pin side force b m Distance between drum centre point and hydraulic cylinder c m Distance between drum centre point and tangential force C* Brake shoe factor C1 Brake shoe factor at primary shoe C2 Brake shoe factor at secondary shoe e N Control error Force difference between modeled and actual forces E J Brake energy F N Applied force L m Band length m kg Vehicle mass N N Normal force N1 N Normal force at primary shoe N2 N Normal force at secondary shoe R N Brake force r m Drum radius R1 N Brake force at primary shoe R2 N Brake force at secondary shoe Ractual N Measured brake force Rmod N Modeled brake force S N Side force S1 N Side force at floating link from primary shoe side S2 N Side force at floating link from secondary shoe side α deg Self amplification angle δ deg Inclination of floating link to x-direction µ Coefficient of friction 1 1 Introduction Ever since the invention of the wheels thousands years ago, it was required to slow down or stop the wagon. Firstly, there were horse wagons and the animals were the only power source. They were not only used to accelerate but also to slow down and to completely stop the wagon. Later on, mechanical means were used to stop the vehicle such as a braking system consisting of a hand lever to push a wooden friction directly against the metal trade of the wheels. There were many inventions to develop braking systems, for example the rope brakes developed around 100 AD or chariot braking systems depending on a wrapped chain around the protruding wheel hub with one end anchored to the chariot body to stop it. The early years of automotive industry were an interesting period for design engineers. Braking system design was one of the important features that determined the limiting speed of the vehicle. Drum brakes were common in the first generation of the vehicle. The drum brake consisted of two shoes which could be expanded inside the drum. In 1902 in England Dr. F. W. Lanchester introduced the first disc brake patent. Disc brakes were firstly produced for the Lanchester car in the period between
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