CONTROL OF SPACECRAFT FORMATION FLYING AROUND ASTEROIDS by Arthur Kar Leung ...

194 Pages·2014·3.52 MB·English

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
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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.

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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.

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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.

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