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Annisthesis.Pdf (709.0Kb) Development of a Visual Demonstration Platform for Parallel Evaluation of Active Suspension Systems Nathanael Douglas Annis Thesis submitted to the Faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of the requirements for the degree of Master of Science in Mechanical Engineering Approved: Dr. Steve Southward Dr. Mehdi Ahmadian Dr. John Ferris November 29, 2006 Blacksburg, Virginia Key words: Suspension, Active, Bond graph, Actuator, Skyhook Development of a Visual Demonstration Platform for Parallel Evaluation of Active Suspension Systems Nathanael Douglas Annis ABSTRACT Vehicle suspensions have been a major focus of research and design since the introduction of the automobile. The two major characteristics that define the performance of a specific suspension design are the vehicle ride and handling. A simplified view of chassis development is that a desirable vehicle ride is provided by a “soft” suspension, and desirable vehicle handling is provided by “stiff” suspensions, it is impossible to simultaneously maximize both vehicle ride and handling in a passive suspension design. However, with the introduction of active components, such as actuators and semiactive dampers, coupled with dynamic control strategies, a more desirable compromise between the benefits of soft and stiff suspensions can be achieved. The purpose of this research is not to create a better suspension, but to investigate how active control can improve vehicle ride. As with any research area, a method for evaluating new ideas is required. Many computational methods exist for determining the ride performance of various suspension designs, however computational results alone can be hard to interpret and often deceiving. The following thesis outlines the design and validation of an experimental test rig for evaluating fully active or semi–active suspension algorithms. The test rig utilizes a fully active electromagnetic actuator which can simulate the performance characteristics of fully active as well as semiactive components which a suspension design may utilize. The demonstration rig couples visual inspection with computational analysis and provides the tools necessary for the designer to accurately interpret the ride performance of a new design and simultaneously compare it with a passive design. The goal is to provide a visual development platform in which new algorithms can be quickly and easily implemented and compared against existing algorithms to determine the performance characteristics of each on a physical system. The test rig demonstrated its ability to test both fully-active and semiactive skyhook control algorithms, and accurately simulated both fully-active and semiactive suspension ii components. The test rig provides a simple and cost effective way to evaluate new algorithms both computationally and visually on a physical system. iii ACKNOWLEDGEMENTS I would like to thank my advisor, Dr. Steve Southward, for his endless support and encouragement throughout my graduate studies in the Mechanical Engineering Department. I would also like to thank Dr. Mehdi Ahmadian and Dr. John Ferris for serving on my graduate Committee and providing assistance and support throughout this process. I would also like to thank my wife, Kara for her endless support and understanding, you have made this possible. Without the lifelong support from my parents Cynthia and Charles, this would not have been possible, and I am eternally grateful. Lastly, I would like to thank my siblings Erik, Jennifer, Rebekah, and Micah for always being there for me. iv CONTENTS Abstract...................................................................................................ii Acknowledgements................................................................................iv Contents ..................................................................................................v List of Figures........................................................................................vi Nomenclature...................................................................................... viii 1 Introduction .......................................................................................1 1.1 Literature Review........................................................................................................ 2 2 Dynamic Model..................................................................................4 2.1 Bond Graph................................................................................................................. 6 2.2 State Space System.................................................................................................... 10 3 Test Rig Construction......................................................................13 3.1 Base Construction...................................................................................................... 13 3.2 Vehicle Construction................................................................................................. 14 3.3 Instrumentation.......................................................................................................... 16 3.4 Signal Integration...................................................................................................... 18 4 Model Parameterization..................................................................20 5 Control System.................................................................................23 5.1 Fully Active Skyhook................................................................................................ 25 5.2 Semiactive Skyhook.................................................................................................. 28 5.3 Skyhook Response Summary.................................................................................... 36 6 Experimental Validation.................................................................38 6.1 Passive Results.......................................................................................................... 38 6.2 Fully Active Results .................................................................................................. 40 6.3 Semiactive Results.................................................................................................... 44 7 Conclusion ........................................................................................49 References .............................................................................................51 Appendix...............................................................................................55 v LIST OF FIGURES Figure 2-1. System Sketch .............................................................................................................. 4 Figure 2-2. Schematic diagram of dynamic system........................................................................ 6 Figure 2-3. First bond graph of dynamic system ............................................................................ 7 Figure 2-4. Full bond graph of dynamic system............................................................................. 8 Figure 2-5. Rolling road dynamic model...................................................................................... 10 Figure 3-1. Test rig base structure ................................................................................................ 13 Figure 3-2. Roller design .............................................................................................................. 14 Figure 3-3. Active (a) and passive (b) suspension designs........................................................... 15 Figure 3-4. Variable air damper.................................................................................................... 15 Figure 3-5. Passive and active suspension components................................................................ 16 Figure 3-6. Vehicle accelerometer mounting locations ................................................................ 17 Figure 3-7. Vehicle accelerometer mounting locations ................................................................ 17 Figure 3-8. Input accelerometer mounting location...................................................................... 18 Figure 3-9. Plot of custom integrator............................................................................................ 19 Figure 4-1. Optimized response of sprung mass........................................................................... 21 Table 4-2. System parameters....................................................................................................... 22 Figure 5-1. Schematic diagram of skyhook control...................................................................... 23 Figure 5-2. Simulink implementation of closed-loop system....................................................... 24 Figure 5-3. Simulink discrete time vehicle model........................................................................ 25 Figure 5-4. Simulink implementation of fully active skyhook control......................................... 26 Figure 5-5. Simulink fully-active skyhook control acceleration response ................................... 27 Figure 5-6. Simulink fully-active skyhook control velocity response.......................................... 28 Figure 5-7. Simulink baseline semiactive skyhook control.......................................................... 29 Figure 5-8. Simulink simulation
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