CONTROL OF SPACECRAFT FORMATION FLYING AROUND ASTEROIDS by Arthur Kar Leung LIN B. Eng., Aerospace Engineering, Ryerson University, 2007 M.A.Sc., Aerospace Engineering, Ryerson University, 2009 A dissertation presented to Ryerson University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in the Program of Aerospace Engineering Toronto, Ontario, Canada, 2014 ©Arthur Kar Leung LIN 2014 All rights reserved ii Author’s Declaration I hereby declare that I am the sole author of this dissertation. This is a true copy of the dissertation, including any required final revisions, as accepted by my examiners. I authorize Ryerson University to lend this dissertation to other institutions or individuals for the purpose of scholarly research. I further authorize Ryerson University to reproduce this dissertation by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research. I understand that my dissertation may be made electronically available to the public.   iii iv Abstract CONTROL OF SPACECRAFT FORMATION FLYING AROUND ASTEROIDS Arthur Kar Leung Lin, Doctor of Philosophy, Aerospace Engineering Ryerson University, Toronto, June 2014 There exist thousands of different minerals and other possible resources out in space. To exploit these resources and to further expand our knowledge of the universe, planetary exploration has opened new gates towards mankind. There are more than one hundred thousand designated asteroids located inside the asteroid belt. Some of these asteroids are as old as the Big Bang itself. Tracking of astronomical bodies such as asteroids is the new stream of research that has attracted a lot of attention. However, due to environmental constraints around asteroids, monolithic spacecraft missions seem challenging. Multi-agent systems, on the other hand, provide significant advantages when it comes to orbiting around asteroids. In this study, novel consensus algorithms are applied to regulate the multi-agent decentralized formation flying for increased system flexibility and reliability. A nonlinear controller is developed to control the decentralized formation flying system of interest. Faults are evaluated and reduced to a minimum when planning a mission. However, the performance of the controller should not be affected when faults occur. For this reason, sensor and actuator faults are examined in this thesis in conjunction with actuator limitations which is commonly referred to as saturation. The proposed control law is not only able to control the system while faults occur, but rather it is capable of maintaining system stability in the presence of time variant external disturbances. Uncertainty in parameters and dynamic models are inevitable due to the complexity of the relatively new mission and lack of experimental data about the system dynamics. As such, a novel adaptive robust control methodology is developed that does not require full knowledge of the system dynamics. Moreover, the adaptive robust control law is combined with a Chebyshev neural network to overcome system uncertainties. Numerical simulations results along with stability analyses show that the proposed control methodology is capable of reducing the system state error close to zero within 1 orbit when maximum thrust of 5 mN with bounded external disturbance of 3 mN is applied for formation reconfiguration scenarios; these results will be useful for the future formation flying missions around asteroids.   v vi Acknowledgements I would like to express my sincere gratitude to my supervisor, Professor Krishna Dev Kumar, for his timely guidance, encouragement and support. 5 years ago, I was a rookie in space system dynamics and control discipline. If not because of Dr. Kumar, I would not be able to work on such an innovative topic and complete this wonderful dissertation. Thank you for helping me getting through all these challenging “rocket science” problems, and for your guidance and counsels that helped me make significant contributions in the field of Spacecraft Dynamics and Control. Your judicious suggestions made the successful completion of this thesis possible. I would like to extend this appreciation to Professor Puren Ouyang, Professor Anton de Ruiter and Professor Simant R. Upreti for their invaluable comments as members of my dissertation committee. I am grateful to my colleagues and friends with whom I had the greatest time. Names are not provided because they know who they are. Exclusive thanks to Siavash Khajehhasani and Sobhan Etemadi. They have been the best possible mentor in every sense of the word. Without that time table you, Siavash, set up for me, I would not be able to complete my thesis. Even though, I don’t have my 6 pack yet, I can do hand stand, cart wheel, pull up, 90 lbs bench press, all and all that I can almost have another PhD degree in gymnastics. Sobhan, you make me a stronger man literally. I give my special appreciation to Janaya Denys for the careful proof-reading of my thesis. She made this thesis much more readable. I would like to take this opportunity to thank my parents Raymond Chun-Lau Lin, and Lucenla Lai-King Lin Wong who deserve special recognition for their continuous encouragement and selfless support. In the path to this success, I have been fallen thousands of time, if not because of my parents, I won’t have the strength and perseverance to reach my current status.   vii viii gÉ `ç _Éä|Çz ctÜxÇàá? f|áàxÜ? YÜ|xÇwá tÇw YtÅ|Äç   ix x