PLENARY SPEAKERS Monday, August 29, 2005 N. Harris McClamroch, University of Michigan: “Pendulum Dynamics and Control Problems: The Planar Pendulum, the Spherical Pendulum and the 3D Pendulum” The classical planar pendulum has long been the paradigm for characterizing dynamic regularity, and its influence on technology has been profound. The planar pendulum has been a key academic example, motivating a vast amount of research on dynamics and control. The spherical pendulum, a 2D generalization of the planar pendulum, has also motivated dynamics and control research. A brief review is given of dynamics and control problems, and selected results, for the planar pendulum and for the spherical pendulum. The 3D pendulum consists of a rigid body, supported at a fixed, frictionless pivot, with three rotational degrees of freedom. A gravitational force and, perhaps, control forces and moments act on the pendulum; the center of mass of the pendulum is assumed to be distinct from the location of the pivot. Several different 3D pendulum models are introduced and used to analyze properties of the uncontrolled 3D pendulum dynamics: conservation properties, equilibria, relative equilibria, local stability properties, and global dynamics properties. Several feedback stabilization problems are proposed, and controllers are introduced that provide asymptotic stabilization of a specific equilibrium. The 3D coupling and the global dynamics of the 3D pendulum give rise to new dynamics and control challenges. An experimental laboratory facility, the triaxial attitude control testbed, is described and selected experimental results obtained to date are summarized. Concluding comments are made about the importance of pendulum models as academic benchmarks. It is suggested that 3D pendula are closely related to difficult problems that occur for robots and space vehicles. N. HARRIS MCCLAMROCH received his Ph.D. degree in Engineering Mechanics, from The University of Texas at Austin. Since 1967 he has been at The University of Michigan, Ann Arbor, Michigan, where he is a Professor and past Chair of the Department of Aerospace Engineering. He is also a Professor in the Department of Electrical Engineering and Computer Science. The main theory areas of his research have included: robustness, optimal control, digital feedback, statistical estimation, stochastic control, and nonlinear control. He has worked on projects that arise from many different engineering applications, including flexible space structures, constrained robotics, automated manufacturing, control technologies for buildings and bridges, rotorcraft guidance using computer vision, spacecraft docking, nonlinear flight control, underactuated and nonholonomic mechanical systems, spacecraft attitude control, and full body problems in astrodynamics. Dr. McClamroch is a Fellow of the IEEE, he received the Control Systems Society Distinguished Member Award, and he is a recipient of the IEEE Third Millennium Medal. He was an Associate Editor and subsequently the Editor of the IEEE Transactions on Automatic Control. He served as Program Chair for the 1994 Conference on Decision and Control and as General Chair of the 1999 Conference on Control Applications. He has held numerous administrative positions in the IEEE Control Systems Society, including Vice President for Publication Activities, Vice President for Financial Activities, and President of the Society.

Tuesday, August 30, 2005

Robert E. Skelton, University of California at San Diego: “Dynamics and Control of Tensegrity Systems”

The now classical ``Composite materials'' concept was to create static bulk properties that are not achievable with any of the constituent members alone. This research seeks to take the next giant leap, to create dynamic bulk mechanical, hydrodynamic, aerodynamic, acoustic, or electromagnetic properties that are not achievable with any of the constituent members alone. The key to this is the use of a material paradigm, known as tensegrity structures. These topologies are composed of rigid bars connected with elastic strings. The dynamic model has the form of a matrix differential equation that does not require inverting a variable mass matrix. We will describe the analytical and numerical tools developed thus far that enable engineers to design materials to have specified: 1) dynamic mechanical properties, such as changing its stiffness or its volume by a factor of hundred, 2) hydro and aerodynamic properties, such as to reduce drag, 3) acoustic properties to suppress, enhance, or alter sound reflections, 4) electromagnetic properties, such as negative permeability and negative permittivity, to alter optical or other reflection or radiation properties.

ROBERT E. SKELTON received his BSEE degree from Clemson University in 1963 and his Ph.D. degree from the University of California at Los Angeles in 1976. He began his career at the Marshall Space Flight Center, working first with Lockheed Missiles and Space Company and then Sperry Rand for 12 years. From 1975-1996, he was a professor of aeronautics and astronautics at Purdue University. He is a Fellow of AIAA and IEEE. He was the 1991 Russell Severence Springer Professor at the University of California at Berkeley. For five years, he served on the National Research Council's Aeronautics and Engineering Board. He served on the External Independent Review Team for the second servicing mission of the Hubble Space Telescope, and is now serving on this team for the next servicing mission. He has published three books and over four hundred papers. Recently, Dr. Skelton's work has focused on integrating system science and material science to create material systems. This is best accomplished using the tensegrity paradigm. Tensegrity is a malleable, flexible and adaptable structure which is composed of continuous strings and sticks. Based on the molecular structure of a spider's fiber, it can change shape by modifying the string tension. The easily adaptable features of tensegrity allow Materials Systems to be created that can modify their acoustic properties, their electromagnetic properties, and their mechanical properties. Tensegrity structures could be deployed into space as light-weight antennae, mirrors and satellites, or be used for airplane wings, water craft or anything else that needs to change shape to reduce drag. Built-in actuators, sensors and power storage devices make tensegrity structures a very attractive alternative to conventional designs for material systems.

Wednesday, August 31, 2005

Banavar Sridhar, NASA Ames Research Center: “Application of Control System Concepts to Large Complex Engineering Systems: Can we help to transform Global Air Traffic Flow?” A safe and efficient aviation industry is vital to the global economy. The growing traffic demand, rise in oil prices, delays in building new runways and security issues are putting pressures on the system to evolve from the current procedure-based human-centered system to a more flexible system with higher levels of automation. Air Traffic Management (ATM) involves several layers of decision-makers scattered between the service providers (Airports and FAA in the United States), Airlines, General Aviation, Cargo Carriers and other users of airspace. Several types of uncertainties are pervasive in the system. This talk will describe the characteristics of the ATM from a control engineer’s point-of-view, discuss problem areas in the current system and point opportunities for improving the system behavior using methods and technology based on systems and control concepts. BANAVAR SRIDHAR received his B.E. degree in Electrical Engineering from the Indian Institute of Science and his M.S. and Ph.D. degrees in Electrical Engineering from the University of Connecticut. He worked at Systems Control, Inc., Palo Alto, Ca and Lockheed Palo Alto Research Center before joining NASA Ames Research Center in 1986. At NASA, Dr. Sridhar has led projects on the development of automation tools for rotorcraft and other vehicles. Currently, he serves as Chief, Automation Concepts Branch, managing research activities in Advanced Air Transportation Technologies. His research interests are in the application of modeling and optimization techniques to aerospace systems. Dr. Sridhar received the 2004 IEEE Control System Technology Award for his contributions to the development of modeling and simulation techniques for multi-vehicle traffic networks and advanced air traffic system. He is a Fellow of the IEEE and the AIAA.