Department of Civil and Environmental Engineering Stanford University DECENTRALIZATION OF WIRELESS MONITORING AND CONTROL TECHNOLOGIES FOR SMART CIVIL STRUCTURES by Jerome Peter Lynch Report No. 140 August 2002 The John A. Blume Earthquake Engineering Center was established to promote research and education in earthquake engineering. Through its activities our understanding of earthquakes and their effects on mankind’s facilities and structures is improving. The Center conducts research, provides instruction, publishes reports and articles, conducts seminar and conferences, and provides financial support for students. The Center is named for Dr. John A. Blume, a well-known consulting engineer and Stanford alumnus. Address: The John A. Blume Earthquake Engineering Center Department of Civil and Environmental Engineering Stanford University Stanford CA 94305-4020 (650) 723-4150 (650) 725-9755 (fax) earthquake @ce. Stanford.edu http://blume.stanford.edu ©2003 The John A. Blume Earthquake Engineering Center DECENTRALIZATION OF WIRELESS MONITORING AND CONTROL TECHNOLOGIES FOR SMART CIVIL STRUCTURES A DISSERTATION SUBMITTED TO THE DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING AND THE COMMITTEE ON GRADUATE STUDIES OF STANFORD UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Jerome Peter Lynch August 2002 ii Copyright 2002 by Jerome Peter Lynch All Rights Reserved iii Abstract A smart civil structure is defined by sensing and/or actuation technologies embedded within the system to provide insight to the structure’s response and an opportunity to limit responses. The past thirty years have been characterized by a revolution in the field of smart structure technologies with sensors and actuators both reducing in size, power demands and unit costs. The efforts of this study have been chiefly focused upon two aspects of smart structure technologies: the development of a wireless monitoring system for structural health monitoring applications and decentralized structural control. The benefits of installing a monitoring system in a structure are multiple, including opportunities to assess the health of the structural system over its expected lifespan. Historically, monitoring systems for civil structures are wire-based and employ hub- spoke system architectures; unfortunately, their high installation and maintenance costs prevent them from becoming widely adopted. Using available technologies from the marketplace, a low cost alternative to traditional wire-based sensing systems has been developed. The unit’s key features include wireless communications, a 16-bit digital conversion of interfaced sensors, and a computational core that can perform various data interrogation techniques in near real-time. As a means of system validation, various performance tests were performed including installation in the Alamosa Canyon Bridge, New Mexico. Structural control systems can be used to limit the response of structures during external disturbances such as strong winds or large seismic events. As the trend of control devices progresses towards smaller and cheaper actuators, structural control systems will be characterized by large actuation densities. The resulting large-scale dynamic system iv is best controlled by decentralized control approaches. Various decentralized control techniques are considered including market-based control (MBC) and energy market- based control (EMBC). Originating from the realm of econometric optimization, the structural system is modeled as a marketplace of buyers and sellers that leads to an optimal control solution. The approach, implemented in various analytical models, exhibits control performances comparable to the centralized linear quadratic regulation (LQR) controller. One distinct advantage of EMBC is its robustness qualities with respect to actuation failures in the control system. v Acknowledgments An endeavor of this nature and magnitude cannot be attempted without the support of a wide cast of family and friends. First, I would like to thank my parents for their encouragement over the years and support during all of the challenges I have ever faced. My strength to see this task through to the end serves as a tribute to them. My brother, Stephen, and sister, Elizabeth, both have been incredibly supportive and helpful during this journey. I will forever be indebted to my advisor and friend, Professor Kincho Law, for helping me find an area of intellectual pursuit that fit my abilities and interests perfectly. Having learned under his tutelage helped me to grow both intellectually and as a person. Having an opportunity, while at Stanford University, to work with some of the best researchers in the world has been a real treat. Many thanks are owed to Professor Ed Carryer for unselfishly sharing with me his encyclopedic knowledge of embedded systems. I am grateful to Professor Anne Kiremidjian and Professor Thomas Kenny, for their endless contribution of ideas and insights that resulted in bettering my efforts to design wireless modular monitoring systems. I would also like to thank Professor Stephen Rock for opening my eyes to the beautiful world of control theory and control system design. Special thanks is owed to Doctor Erik Straser who laid the foundation for my research with his groundbreaking dissertation work on wireless monitoring systems for structures. During the summer of 1998, I had the unique opportunity to study the theoretical and practical aspects of structural control in Japan through the National Science Foundation’s Summer Institute in Japan program. As a visiting researcher at Kajima vi Corporation’s Kobori Research Complex, I was honored to interact with some of the visionaries in the field of structural control, particularly Doctor Tomohiko Hatada, Mr. Akihiro Kondo and Doctor Narito Kurata, an opportunity that comes along only once in one’s lifetime. I am indebted to Doctors Charles Farrar and Hoon Sohn of Los Alamos National Labs for providing me with invaluable insight into the world of structural health monitoring and damage detection algorithms for civil structures. They are responsible for providing access to the Alamosa Canyon Bridge as a validation deployment of the wireless sensing units. I thank Doctors Andrew Berlin and Warren Jackson, formerly of the Smart Matter group at Xerox PARC, for helping me get started with applying marketplace pricing and economic competitive equilibrium concepts to the problem of control in structural systems. The long path I have journeyed since enrolling as a civil engineering student at Cooper Union has been brightly lighted by the passion and integrity of two role models: Doctor Robert Smilowitz of Weidlinger Associates and Doctor Therios Lefcochilos of Saudi Aramco. They serve as examples of what the noble profession of structural engineering embodies. I thank all of my friends in the Engineering Informatics Group (EIG) for helping me with various aspects of my research, particularly David Liu, Chuck Han, Shawn Kerrigan, Gorie Lau, Yang Wang, Brian Flaherty and Arvind Sundararajan. Some of my fondest memories of Stanford will be of my time spent at the John A. Blume Earthquake Engineering Center. The intellectual and social interactions with all of the students in the Blume Center made many late nights enjoyable. I am particularly thankful to Nicolas Luco, Ricardo Medina, Fatemeh Jalayer, Babak Alavi-Shushtari, Medji Sama, Paul Cordova, Scott Hamilton, Jackie Lai, and Racquel Hagen. vii Finally, I want to express my deepest and sincerest gratitude for the support provided by Nadine Wong Shi Kam, Mishka Priven, Jun Peng, and Sam King. The entire Stanford experience would not have been the same without them. This research is sponsored and supported by the National Science Foundation, Grant Numbers CMS-9988909 and CMS-0121842. Additional support has been provided by the National Defense Science and Engineering Graduate Fellowship provided by the U.S. Department of Defense and administered by the Department of the Navy, and the Stanford Graduate Fellowship. viii Table of Contents Abstract.............................................................................................................................iv Acknowledgments.............................................................................................................vi Table of Contents..............................................................................................................ix List of Tables ..................................................................................................................xiv List of Figures..................................................................................................................xv 1 Introduction..................................................................................................................1 1.1 Smart Structure Technology ..............................................................................1 1.1.1 Structural Monitoring............................................................................................... 2 1.1.1.1 System Architecture ........................................................................................ 3 1.1.1.2 Cost of Structural Monitoring ......................................................................... 4 1.1.1.3 Limitations of Current Structural Monitoring Systems................................... 5 1.1.2 Structural Control....................................................................................................