Robotic Rock Classification and Autonomous Exploration
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Robotic Rock Classification and Autonomous Exploration Liam Pedersen Acknowledgements A tremendous debt of gratitude is due to the many people who assisted or contributed in different ways to this research. The Robotic Antarctic Meteorites Search project was a team effort, involving many people, all of who deserve credit for the project’s success. Firstly, thanks go to my thesis committee: Martial Hebert, Red Whittaker, Andrew Moore, Reid Simmons and Peter Cheeseman, for their time and effort. Martial Hebert, my academic advisor, has carefully nurtured this thesis and steadily kept me on track over the last few years. In spite of a busy schedule, he has always selflessly managed to make time to help make this research happen, write references, and generally smooth the way. All this in spite of not being directly involved with, or receiving direct credit for the successes of the Robotic Antarctic Meteorite Search project. Dimitrious Apostolopoulos, as project manager for the Robotic Antarctic Meteorite Search project tirelessly and consistently backed my research. Without his leadership and tenacity, the project would not have been completed and this research would not have been possible. William “Red” Whittaker, as director of the Field Robotics Center, has supported this project and my research throughout. His tenacity and experience at handling funding agencies ensured essential financial support, and his counsel has been invaluable both in the preparation of this document and in furthering this research. Dr. Ted Roush was happy for me to spend three summers at NASA’s Ames Research Center working with him on rock classification and spectroscopy. His continuous generosity and support have helped me tremendously with this research. He spent substantial time explaining fundamental geology and spectroscopy, and made available, at an inconvenience to himself, a marvelous spectrometer with which to study rocks in Antarctica. Dr. Bill Cassidy’s unstinting help and commitment to the cause of the Robotic Antarctic Meteorite Search were invaluable. I first met Bill at the beginning of the project, when I naïvely asked how to recognize meteorites. Bill nodded wisely and, every bit the wise veteran Antarctic explorer, told me “First you find a few, then you know what to look for”. Soon followed by “meteorites are where you find them”. Thus began a fruitful partnership, during which Bill patiently explained a lot of basic geology to me, loaned me his personal collection of meteorites, identified Antarctic rocks and was a paragon of dignity and humor under extreme conditions on the Antarctic ice sheets. Dr Gunter Faure of Ohio State University generously made his collection of Antarctic rocks from Elephant Moraine available for this research. Without this assistance it would not have been possible to prepare for the Elephant Moraine expedition. Dr Marilyn Lindstrom and the staff of the Antarctic meteorite curation facility at NASA’s Johnson Space Center gave me invaluable access to the Antarctic meteorite collection. The meteorites are kept in a clean room and are handled according to strict protocols. Lindstrom and others spent many hours with me in the clean room, patiently preparing the meteorites and helping me acquire spectral measurements crucial for this research. Pascal Lee, Mathew Deans, Kurt Schwehr, Michael Parris, Mark Sibenac, Stewart Moorehead and Alex Foessel spent significant time in the field with me, measuring and collecting rocks on the Antarctic ice sheet. In spite of extreme conditions they always maintained a sense of humor, patience and professionalism. It was a pleasure and a privilege to work with them. Michael Wagner and Ben Shamah kept the Nomad robot running in the field during the final trials. Mike was primarily responsible for the software operating Nomad, and spent considerable time with me to integrate my software with the vehicle. Ben designed and built the manipulator arm on Nomad, worked ceaselessly to build the mechanical parts and managed the logistics of the final operations in Antarctica. Their dedication and professionalism are impressive. Gretchen Benedix helped to identify and characterize many of the rock samples that were collected. Ralph Harvey and John Schutt of ANSMET respectively gave me a lot of advice about Antarctica and kept us out of trouble in the field. John is the gold standard to which all meteorite hunters (human or robotic) aspire. His ability to spot an extra-terrestrial rock at a thousand paces is impressive. Dot Marsh worked behind the scenes in so many ways to smooth things over and grease the wheels of academic progress. Without her help, consideration, cheerfulness and occasional prod in the back to wake me up things would have been very different. Finally, last, but by no means least, I must thank my family and friends for their continued encouragement and support throughout. My mother was always available and understanding. Chris Scarpinatto would periodically drag me away from the computer to make sure I was eating properly, had enough vegetables and could decompress a little. My neighbors Nick and Jo- Anne Redondo would send their children around with food for a certain thin (possibly starving) graduate student next door. Contents Chapter 1. Introduction............................................................................................................................. 6 1.1. Robotic Antarctic Meteorite Search (RAMS) project.................................................................. 7 1.1.1. Meteorites and the Antarctic environment .............................................................................. 8 1.2. Prior work .................................................................................................................................. 11 1.3. Contributions ............................................................................................................................. 12 1.4. Thesis outline............................................................................................................................. 12 1.5. References.................................................................................................................................. 12 Part I................................................................................................................................................... 15 The Bayesian Paradigm for Robotic Rock Classification............................................................................. 15 Chapter 2. Robotic Rock Classification.................................................................................................. 16 2.1. Issues in robotic rock and meteorite classification .................................................................... 16 2.2. Bayes network generative model............................................................................................... 20 2.2.1. Notation ................................................................................................................................ 20 2.2.2. Generative and diagnostic statistical models ........................................................................ 21 2.2.3. Bayes networks ..................................................................................................................... 23 2.3. Other classification systems....................................................................................................... 24 2.4. Conclusions................................................................................................................................ 26 2.5. References.................................................................................................................................. 27 Chapter 3. Bayes network classifier topology ........................................................................................ 28 3.1. Naïve Bayes architecture ........................................................................................................... 28 3.2. Naïve Bayes network with intermediate nodes.......................................................................... 29 3.3. Bayes network with weak data dependencies and intermediate node........................................ 31 3.4. The rock and meteorite Bayes network classifier ...................................................................... 32 3.5. References.................................................................................................................................. 33 Chapter 4. Bayes Network Training ....................................................................................................... 35 4.1. Bayesian parameter learning...................................................................................................... 35 4.1.1. Learning probabilities from uncertain data ........................................................................... 38 4.2. Quantization of continuous parameters and the “Curse of dimensionality” .............................. 39 4.2.1. Sensor noise models.............................................................................................................. 41 4.3. Laboratory training results......................................................................................................... 41 4.4. References.................................................................................................................................. 43 Part II ...............................................................................................................................................