Motion Coordination of Multiple Autonomous Vehicles in a Spatiotemporal Flowfield

Title of dissertation: MOTION COORDINATION OF MULTIPLE AUTONOMOUS VEHICLES IN A SPATIOTEMPORAL FLOWFIELD Cameron Kai Peterson, Doctor of Philosophy, 2012 Dissertation directed by: Professor Derek Paley Department of Aerospace Engineering The long-term goal of this research is to provide theoretically justified control strategies to operate autonomous vehicles in spatiotemporal flowfields. The specific objective of this dissertation is to use estimation and nonlinear control techniques to generate decentralized control algorithms that enable motion coordination for multiple autonomous vehicles while operating in a time-varying flowfield. A cooperating team of vehicles can benefit from sharing data and tasking responsibilities. Many existing control algorithms promote collaboration of autonomous vehicles. However, these algorithms often fail to account for the degradation of control performance caused by flowfields. This dissertation presents decentralized multivehicle coordination algorithms designed for operation in a spatially or temporally varying flowfield. Each vehicle is represented using a Newtonian particle traveling in a plane at constant speed relative to the flow and subject to a steering control. Initially, we assume the flowfield is known and describe algorithms that stabilize a circular formation in a time-varying spatially nonuniform flow of moderate intensity. These algorithms are extended by relaxing the assumption that the flow is known: the vehicles dynamically estimate the flow and use that estimate in the control. We propose a distributed estimation and control algorithm comprising a consensus filter to share information gleaned from noisy position measurements, and an information filter to reconstruct a spatially varying flowfield. The theoretical results are illustrated with numerical simulations of circular formation control and validated in outdoor unmanned aerial vehicle (UAV) flight tests. MOTION COORDINATION OF MULTIPLE AUTONOMOUS VEHICLES IN A SPATIOTEMPORAL FLOWFIELD by Cameron Kai Peterson Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2012 Advisory Committee: Dr. Derek A. Paley, Chair/Advisor Dr. Robert M. Sanner Dr. J. Sean Humbert Dr. David L. Akin Dr. Balakumar Balachandran, Dean’s Representative c © Copyright by Cameron Kai Peterson 2012 Acknowledgments I wish to thank my adviser, Dr. Derek Paley for his guidance, knowledge and time. He encouraged and supported me, gave me feedback on the problems and possibilities, made invaluable suggestions to correct and clarify my work, and patiently guided me through the process of completing my Ph.D. I am indebted to him for working with my non-traditional time constraints and never giving up on me throughout this process. I am also grateful to my employer, the Johns Hopkins University Applied Physics Laboratory (JHU/APL) for the financial support and flexible work schedule that enabled me to complete this degree. They also let me use their equipment so that I could complete my flight experiments. I am indebted to Jon Castelli who spent a great deal of time helping me set-up the hardware simulators, answering multitudes of questions, and overseeing flight experiments. I am also appreciative of others who helped me with technical issues and conducting experimental flights – especially Mike Conner, Jeff Barton, Levi DeVries, and Mike Foust. I am grateful to a number of associates who gave me valuable advice and feedback on my work, particularly Pat Murphy, Eric Frew, Pedro Rodriguez, Andy Newman, Jeromy McDerment, Lazlo Techy, and Sachit Butail. I also appreciated the help of my friends in the CDCL group, Levi, Seth, Nitn, Tracy, Amanda, Sonia, Sachit, and Rochelle. To these and others who have offered encouragement and given assistance of any kind, I express appreciation. Finally, I would like to thank my family and friends for their enduring support. My friends kept me fed and ran my errands when I was too busy, pulled me away from work when I needed a break and displayed plenty of enthusiasm whenever I managed to draw yet another circle. Huge thanks to Claire, JP, Heather, Adam, Tyler, Mikale, Ali, Jake, Nicole and Jill. My parents and siblings have also incredibly supportive. I would like to thank my mother, Lucille Peterson, for teaching me that education should always be a lifelong pursuit and my father, Eugene Peterson, for his encouraging stories of hurricanes, current bushes, and failed Shakespeare classes. I am grateful for their encouragement and devotion to me. This work was partially funded by the Office of Naval Research under grant N00014-09-1-1058 and National Science Foundation under grant CMMI0928416.