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Topics in Guided Motion Control of Marine Vehicles Thesis for the degree of philosophiae doctor
Trondheim, June 2010
Norwegian University of Science and Technology Faculty of Information Technology, Mathematics and Electrical Engineering Department of Engineering Cybernetics
NTNU Norwegian University of Science and Technology Thesis for the degree of philosophiae doctor Faculty of Information Technology, Mathematics and Electrical Engineering Department of Engineering Cybernetics Morten Breivik ISBN 978-82-471-2084-2 (printed ver.) ISBN 978-82-471-2085-9 (electronic ver.) ISSN 1503-8181 ITK Report 2010-7-W Doctoral Theses at NTNU, 2010:63 Printed by Tapir Uttrykk
This thesis is dedicated to my wife Siri as a token of my love and admiration.
Summary A mix between a monograph and an article collection, this PhD thesis considers the concept of guided motion control for marine vehicles, in particular focusing on underactuated marine surface vehicles. The motion control scheme is defined to involve the combination of a guidance system which issues meaningful velocity commands with a velocity control system which has been specifically designed to take vehicle maneuverability and agility constraints into account when fulfilling these commands such that a given motion control objective can be achieved in a controlled and feasible manner without driving the vehicle actuators to saturation. Furthermore, motion control scenarios are classified in a novel way according to whether they involve desired motion which has been defined a priori or not. Consequently, in addition to the classical scenarios of point stabilization, trajectory tracking, path following and maneuvering, the so-called target tracking scenario is considered. The resulting scenarios then involve target tracking, path following, path tracking and path maneuvering. In addition, it is proposed to define the control objectives associated with each scenario as work-space tasks instead of configuration-space tasks. Such a choice seems better suited for practical applications, since most vehicles operate in an underactuated configuration exposed to some kind of environmental disturbances. The thesis also proposes a novel mechanization of constant bearing guidance, which is a classical guidance principle well-known in the guided missile literature. This suggestion is motivated by a need to solve the target tracking motion control objective for marine vehicles. The proposed implementation enables explicit specification of the transient rendezvous behavior toward the target by selection of two intuitive tuning parameters. In addition, a singularity-free guidance law applicable to path following scenarios involving regularly parameterized paths which do not need to be arc-length parameterized is proposed. An extension to this guidance law is also suggested in order to enable off-path traversing of regularly parameterized paths for formation control purposes. A novel velocity control system which inherently takes maneuverability, agility and actuator constraints into account is developed for the purpose of controlling underactuated marine vehicles moving at high speed. The system is derived through a design method which involves a control-oriented modeling approach and requires a minimum of system identification tests to be carried out.
The thesis also gives a novel overview of the major developments in marine control systems as seen from a Norwegian perspective. The development can be viewed as three waves of control, where the first wave concerned development of novel ship automation technology in the 1960s and 1970s, the second wave involved development of unique dynamic positioning systems in the 1970s and 1980s, while the third wave is expected to encompass the development of unmanned vehicle technology for a large number of maritime applications. A summary of the historical development, present status and future possibilities associated with unmanned surface vehicles (USVs) is also given. Current Norwegian activities are particularly emphasized. Furthermore, an overview of the main formation control concepts applicable to marine surface vehicles is given. A novel formation control functionality named coordinated target tracking is subsequently suggested within a leader-follower framework. Employing a guided motion control system using the suggested mechanization of constant bearing guidance, this functionality is then implemented for two different types of underactuated USVs such that they are able to move in formation with a leader vessel which can maneuver freely without being constrained to any predefined motion pattern. In particular, excerpts from successful full-scale formation control experiments involving a manned leader vessel and the two USVs executing coordinated target tracking at high speed are presented. This functionality currently seems to be unique on a worldwide basis, providing a convenient plug-and-play formation control capability for manned leader vessels involved in maritime survey operations.
Preface This thesis is based on research carried out in the period July 2003 through December 2009. From July 2003 through June 2006 my work was financed by a PhD scholarship sponsored by the Norwegian Research Council (NFR) through the Centre for Ships and Ocean Structures (CeSOS) at the Norwegian University of Science and Technology (NTNU) in Trondheim, Norway. From July 2006 through June 2008 I worked as a temporarily engaged assistant professor at the Department of Engineering Cybernetics (ITK) at NTNU, while I have been working partly as a temporarily appointed assistant professor at NTNUs Department of Marine Technology (IMT) and partly as a researcher at CeSOS since July 2008. In addition, I have worked as a scientific advisor for the Trondheim-based company Maritime Robotics from June 2007 through December 2008 on the NFR-sponsored project 175977: Unmanned Surface Vehicle. The financial support from these institutions is gratefully acknowledged. I would particularly like to thank Professor Thor I. Fossen for originally convincing me to embark on a PhD study and for serving as my thesis supervisor. I consider myself very fortunate and privileged to have been brought up professionally under his wings. He has provided me with the freedom to pursue my own ideas, has given me the possibility to travel around the world, and has been very efficient and helpful in dealing with practical issues concerning financing and bureaucracy during my studies. Without his invaluable guidance and continued support, I would not have been where I am today. I would also like to thank Professor Roger Skjetne for inspiring me to start my PhD study through his work on maneuvering theory and his advisory role during the work with my MSc thesis. Professor Asgeir J. Srensen is also thanked for his great advice and continued support during my time at NTNU. In addition, I would like to thank Professor Torgeir Moan, the director of CeSOS, for always having an open door and his willingness to support unconventional research topics. Furthermore, I would like to thank Professor Andrew R. Teel for inviting me to visit the Center for Control Engineering and Computation (CCEC) at the University of California, Santa Barbara (UCSB) in the period September 2005 through April 2006. The US-Norway Fulbright Foundation for Educational Exchange is gratefully acknowledged for financing my stay in the US. Special thanks is due to Maxim V. Subbotin for our joint work on guided formation control as well as the UCSB College Republicans and the International Students Association at UCSB for giving me many fun moments during my stay in California. Richard Schuh is also thanked for showing me just how hospitable Americans can be to newcomers, while Carlos Ortiz and his family always will have a special place in my heart after opening their home to me.
Ive had a great time working with the crew at Maritime Robotics since 2007. This collaboration has given me invaluable insights into the relationship between theory and practice and the unique opportunity to test my motion control ideas in the real world. Many thanks are due to Vegard E. Hovstein, Arild Heps, Eirik E. Hovstein, Stein Johansen, Idar Petersen and Kristin Sundfr Schive. In addition to those co-authors whose names are mentioned elsewhere in this Preface, I would especially like to acknowledge Jann Peter Strand, Renato Skejic, Alexey Pavlov, Gunnar Sand and Geir Hovland for their efforts on our joint publications. My friends and colleagues at NTNU are thanked for providing a diverse, interesting and stimulating working environment up through the years, in particular Ivar Ihle, Johannes Tjnns, Jostein Bakkeheim, Frank Jakobsen, Andrew Ross, Tristan Perez, Jerome Jouffroy, Jon Refsnes, Kari Unneland, Luca Pivano, Tu Duc Nguyen, Gullik Jensen, Christian Holden, Jrgen Hals, Roberto Galeazzi, Dominik Breu and Anastasios Lekkas. Thanks are also due to those who have joined for football practice each week, especially Torkel Hansen and Stefano Bertelli for organizing the training sessions. Ive also had the privilege of supervising many bright and creative MSc students on their project and thesis work, and would particularly like to mention Benjamin Golding, Jon Alme and ivind Loe. My current group of MSc students should also be thanked for their eagerness and enthusiasm, including Jon-Erik Loberg, ivind Kre Kjerstad, Joakim Haugen, Vetle Vintervold and Per Nord. The administrative staff consisting of Sigrid Bakken Wold and Karelle Gilbert at CeSOS and Tove K. B. Johnsen, Eva Amdahl and Unni Johansen at ITK are thanked for handlin