Aerodynamic Sensing for Autonomous Unmanned Aircraft Systems by Derrick W. Yeo A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Aerospace Engineering) in The University of Michigan 2013 Doctoral Committee: Associate Professor Ella M. Atkins, Co-Chair Professor Wei Shyy, Co-Chair Associate Professor Luis P. Bernal Professor Carlos E. Cesnik Associate Professor Yin Lu (Julie) Young To a young boy, who was so busy playing with aeroplanes that he forgot to grow up. ii Acknowledgements I have had a wonderful time at the University of Michigan and would like to mention the following people in particular, thereby letting everyone know how grateful I am for everything they have done for me. Dr. Atkins: An entire chapter would be needed to adequately express my gratitude for your guidance, support and friendship throughout the years. Thank you for always providing me with a much-needed reality check every time I dropped by your office, in utter despair about some perceived research tragedy or new and exciting character flaw on my part. From midnight laundry madness to midday lawn mowing by way of epic battles with seasickness, our flight-test adventures have always been great fun. Working in your lab has been a wonderful journey and I am grateful for the memories. Dr. Shyy: Thank you for all the encouragement and support you have provided me, in all the years since I first showed up at your office looking to start an aero- modeling club. Your confidence in me has always been inspiring even when I iii inspired little confidence in anyone else. I have a long way to go as a researcher, and will always remember your advice. Dr. Bernal: Thank you for the heroic levels of patience you have shown me over the years since my undergraduate days. In the context of this dissertation, thank you for not throwing me out of your office when I showed up one day waving a screwdriver with two tubes unceremoniously strapped to one end, proclaiming “My beta-probe works!” To my friends and colleagues: Thank you, Ryan and Justin for always providing doses of sanity through the years along with much appreciated servings of humor. The A2Sys motorcycle gang did not last long and broke no laws, but I like to think we were Born to be Wild anyway. Thank you, Cat for always caring enough to provide feedback during practice presentations, even after everyone else had either fallen asleep or discovered the secret of the universe within their phones. Thank you, Roland for taking time off your own work to help me run the vacuum tests, and always being ready to visit a Mediterranean restaurant. Thank you, Dan for showing me the engineering behind the world of artistry and introducing me to the magical world of back-room Computer Aided Manufacturing. Thank you, Jerry for your capable assistance around the lab. To my other friends and loved ones who have supported me over the years, you know who you are: Thank you. And finally, I would like to thank my family. Thank you, Mum and Pa for being my first research sponsors and buying me my first radio controlled aeroplane when I was six. Thank you for listening to the endless complaints from every school teacher I have ever had, and still sending me off to college anyway. Thank you, my dear sister, for having had to bear the brunt of my marvelous stupidity growing up. Thank you all for the patience and loving support you have provided me throughout my thirty one years of childhood. It has been a long time since that first RC flight, but I still always find myself standing about with an aeroplane in my hand and a big smile on my face. iv Table of Contents Dedication ……………………………………………………………………………..ii Acknowledgements …………………………………………………………………….iii List of Tables ........................................................................................................ ix List of Figures ....................................................................................................... x List of Appendices .............................................................................................. xiv Abstract ......................................................................................................... xv Chapter 1 Introduction .......................................................................................... 1 1.1 Motivation ................................................................................................ 2 1.2 Basic challenges and requirements ......................................................... 3 1.3 Research objectives ................................................................................ 4 1.4 Thesis overview ....................................................................................... 5 1.5 Contributions & innovations ..................................................................... 8 Chapter 2 Background........................................................................................ 11 2.1 Aerodynamic lift generation ................................................................... 11 2.2 Traditional approach to aerodynamic force measurements ................... 14 2.3 A pressure-based aerodynamic data system ........................................ 15 2.4 Flapping wing vehicle background......................................................... 18 2.5 High angle of attack, fixed-wing UAS operations ................................... 21 Chapter 3 Pressure Based Aerodynamic Force Estimation for Flapping Wing Vehicles ....................................................................................................... 26 3.1 Introduction ............................................................................................ 26 3.2 Experimental approach .......................................................................... 27 v 3.3 Flapping wing experimental setup ......................................................... 28 3.3.i Flap stand overview ........................................................................ 28 3.3.ii VICON testing instrumentation........................................................ 31 3.3.iii Vacuum chamber test setup and instrumentation. .......................... 32 3.3.iv Wind tunnel test setup and instrumentation .................................... 34 3.4 Flapping wing kinematics ...................................................................... 37 3.4.i Mechanical design and geometry ................................................... 38 3.4.ii VICON motion capture validation of mechanics .............................. 39 3.4.iii 3D Linkage solver and comparison to VICON data ......................... 42 3.5 Multi-phase experimental characterization of loads ............................... 44 3.5.i Vacuum chamber measurements of inertial loads .......................... 44 3.5.ii Wind tunnel vertical force and pressure measurements ................. 45 3.6 Experimental data processing and analysis .......................................... 46 3.6.i Force-Torque sensor data – frequency domain analysis ................ 47 3.6.ii Pressure based aerodynamic force estimation ............................... 56 3.6.iii Comparison of pressure based estimates and force sensor aerodynamic force measurements ............................................................... 60 3.7 Phase and magnitude shifts due to pressure lines ................................ 65 3.8 Forward flight cases .............................................................................. 66 3.8.i Forward flight test procedure .......................................................... 67 3.8.ii Additional data processing for forward flight ................................... 68 3.8.iii Forward flight test results ................................................................ 72 3.9 Summary of test results ......................................................................... 74 3.9.i Comparison of experimental methodologies ................................... 75 3.10 Flapping wing conclusions ................................................................. 77 vi Chapter 4 Aerodynamic Moment Estimation for Fixed Wing Vehicles in High Angle of Attack Maneuvering .............................................................................. 80 4.1 Introduction ............................................................................................ 80 4.2 Steady level flight equations .................................................................. 81 4.3 Proposed linear model for high angle-of-attack flight ............................. 83 4.4 Embedded instrumentation .................................................................... 87 4.4.i Embedded pressure sensors on flight surfaces .............................. 89 4.4.ii Custom designed multi-hole probes ................................................ 91 4.5 Aircraft configuration .............................................................................. 92 4.6 Aerodynamic sensing - tail section ........................................................ 94 4.6.i Dedicated multi-hole probe for prop-wash estimation ..................... 95 4.6.ii Instrumented tail ............................................................................. 97 4.7 Calibration of instrumentation ................................................................ 99 4.7.i Prop-wash probe calibration ........................................................... 99 4.7.ii Tail-surface pressure port and sensor calibration ........................