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Alessandro Astolfi, Imperial College London, UK
Title: Moments of Nonlinear Systems: From Model Reduction to Identification and Circuits Theory
Abstract: The notion of moment for linear systems is generalized to nonlinear, possibly time-delay, systems and to general classes of signal generators (i.e. interpolation points). It is shown that this notion provides a powerful tool for the solution of model reduction problems, for the identification of reduced order model from input-output data and for the analysis of power electronic circuits. In particular, it is shown that moments yield a generalization of the so-called phasor transform to circuits with power electronics components.
Biography: Alessandro Astolfi was born in Rome, Italy, in 1967. He graduated in electrical engineering "cum laude" from the University of Rome in 1991. In 1992 he joined ETH-Zurich where he obtained a M.Sc. in Information Theory in 1995 and the Ph.D. degree with Medal of Honor in 1995 with a thesis on discontinuous stabilization of nonholonomic systems. In 1996 he was awarded a Ph.D. from the University of Rome "La Sapienza" for his work on nonlinear robust control. Since 1996 he has been with the Electrical and Electronic Engineering Department of Imperial College London, London (UK), where he is currently Professor in Nonlinear Control Theory and Head of the Control and Power Group. From 1998 to 2003 he was also an Associate Professor at the Dept. of Electronics and Information of the Politecnico of Milano. Since 2005 he has also been a Professor at Dipartimento di Ingegneria Civile e Ingegneria Informatica, University of Rome Tor Vergata. He has been a visiting lecturer in "Nonlinear Control" in several universities, including ETH-Zurich (1995-1996); Terza University of Rome (1996); Rice University, Houston (1999); Kepler University, Linz (2000); SUPELEC, Paris (2001). His research interests are focused on mathematical control theory and control applications, with special emphasis for the problems of discontinuous stabilization, robust and adaptive control, game theory, observer design and model reduction. He is the author of more than 120 journal papers, of 30 book chapters and of over 240 papers in refereed conference proceedings. He is the recipient of the IEEE CSS A. Ruberti Young Researcher Prize (2007) and of the IEEE CSS George S. Axelby Outstanding Paper Award (2012). He is a "Distinguished Member" of the IEEE CSS. He is the author (with D. Karagiannis and R. Ortega) of the monograph "Nonlinear and Adaptive Control with Applications" (Springer-Verlag). He is Associate Editor of Automatica, the International Journal of Control and Area Editor for the International Journal of Adaptive Control and SignalProcessing. He is Senior Editor of the IEEE Trans. on Automatic Control and Editor-in-Chief of the European Journal of Control. He has also served in the IPC of various international conferences. He is currently the Chair of the IEEE CSS Conference Editorial Board.
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John A. Burns, Virginia Polytechnic Institute and State University, USA
Title: Physics Based Modeling for Design and Control of Thermal-Fluid Systems
Abstract: In this presentation we discuss several modeling and computational issues involved with control of thermal-fluid systems. The problems are motivated by applications to the design and operation of aircraft environmental control systems (ECS) and heating, ventilation, and air conditioning (HVAC) systems for buildings. These systems are typical of many of todays complex multi-physics, data-driven, uncertain physical systems arise in a wide variety of modern engineered systems. Physics based modeling produces mathematical models that are interconnected systems of ordinary and partial differential equations, empirical maps and table look-ups. It is important to keep in mind that if any one of the system’s components is infinite dimensional, then the composite system is infinite dimensional and should be treated as a distributed parameter control system.
Although such systems arise naturally when the problem is multidisciplinary (e.g., aeroelasticity, thermal-fluids) and often requires connecting different types of mathematical equations through boundary conditions, similar issues arise when actuator dynamics are included in the control model. We present examples to highlight some technical issues that occur when dealing with interconnected systems and then focus on a special class of composite systems that occur when actuator dynamics are included as part of the model. Finally, we suggest some new application areas that offer enormous opportunities for researchers interested in distributed parameter control.
Biography: John A. Burns is the Hatcher Professor of Mathematics at Virginia Tech and Technical Director of the Interdisciplinary Center for Applied Mathmatics. He received his B.S.E. and M.S.E. degrees in Mathematics from Arkansas State University (1967 and 1968) and M.S. and Ph.D. degrees in Mathematics from the University of Oklahoma (1970 and 1973). He spent a year as a Research Postdoc Fellow in the Lefschetz Center for Dynamical Systems at Brown University (1973). He has served on more than 12 editorial boards and he was the founding Editor of the SIAM Book Series on Advances in Design and Control. He served as Vice President of SIAM, is the past Chair of the SIAM Activity Group on Systems and Control and is a Fellow of the IEEE and SIAM. In 2012 he was awarded the W.T. and Idalia Reid Prize in Mathematics for his fundamental contributions in computational methods for and applications in control, design and optimization of infinite dimensional dynamical systems. Dr. Burns primary interests concern the development of rigorous and practical computational algorithms for control, optimization and design of complex engineering systems.
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Fariba Fahroo, DARPA, USA
Title: Computational Nonlinear Control Theory: A Path Forward for Meeting the Real World Challenges
Abstract: High performance complex systems prevalent in real world applications demand more powerful computational tools and new rigorous methodologies that could deal with the underlying high-dimensional, nonlinear, multi-layered nature of these systems. For control and design of these systems, existing methodologies fail to accomplish the dual tasks of providing rigor within a computational-based approach. These frameworks are either focused on large-scale simulations without foundations on establishing errors and performance bounds or they are focused on rigorous analysis of much simplified systems that are not representative of the complex systems of interest. To overcome these deficiencies, the new trends in computational control theory based on development of scalable, accurate algorithms for the controlled systems could take the lead in solving some of our outstanding problems such as flow control, control of large networks, design and control of electric power grids and control of swarms among others. In this talk, some of the challenges and approaches will be addressed.
Biography: Fariba Fahroo has joined DARPA Defense Science Office (DSO) since 2014 as a Math program manager. Her prior position has been with the Air Force Office of Scientific Research where she was a program officer for Math programs in Dynamics and Control, Computational Mathematics and Optimization and Discrete Math. While at AFOSR, she initiated and managed basic research programs in various areas of computational math and control theory such as multiscale modeling and computation, uncertainty quantification, design under uncertainty, distributed, multi-agent control and estimation and computational control theory.
Prior to her position at AFOSR, she was a professor of Applied Mathematics at the Naval Postgraduate School. She received her Ph.D. in Applied Math from Brown University, a Master of Arts degree in Mathematics from the University of Wisconsin, Madison, and Bachelor of Arts degrees in Mathematics and Physics from the University of California, Berkeley. Her research interests span control and design of distributed parameter systems and computational methods in control and uncertainty quantification. She is a senior member of IEEE, Associate Fellow of AIAA and is the Chair of the SIAM Control and Systems Theory Activity Group.
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Jorge Cortes, University of California, San Diego, USA
Title: Asymptotic Stability of Saddle-point Dynamics and Its Role in Network Coordination
Abstract: Primal-dual algorithms are saddle-point dynamics for determining the primal and dual solutions of (in)equality constrained convex optimization problems. These dynamics are used to solve problems in multiple scenarios, including network resource allocation in wireless systems, stabilization and optimization in power networks, and distributed learning in games. The specific structure of saddle-point dynamics make them particularly well-suited for solving in a distributed way networked optimization problems that involve aggregate objective functions with constraints that can be expressed locally. In this talk, we examine various conditions under which the set of saddle points is asymptotically stable under the saddle-point dynamics of a continuously differentiable function. Our convergence results are based on different properties of the function such as convexity-concavity, its behavior along the proximal normals to the set of saddle points, and its linearity in one argument. We illustrate our discussion with examples from distributed optimization, network bargaining, and zero-sum games.
Biography: Jorge Cortes is a Professor with the Department of Mechanical and Aerospace Engineering at the University of California, San Diego. He received the Licenciatura degree in mathematics from the Universidad de Zaragoza, Spain, in 1997, and the Ph.D. degree in engineering mathematics from the Universidad Carlos III de Madrid, Spain, in 2001. He held postdoctoral positions at the University of Twente, The Netherlands, and at the University of Illinois at Urbana-Champaign, USA. He was an Assistant Professor with the Department of Applied Mathematics and Statistics at the University of California, Santa Cruz from 2004 to 2007. He is the author of "Geometric, Control and Numerical Aspects of Nonholonomic Systems" (New York: Springer-Verlag, 2002) and co-author of "Distributed Control of Robotic Networks" (Princeton: Princeton University Press, 2009).
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Warren Dixon, University of Florida, USA
Title: Cybernetic Cycling: A Nonlinear Switched Systems Approach to Facilitate Neurological Rehabilitation
Abstract: Application of an electric field across skeletal muscle causes muscle contractions that produce limb movement. Closed-loop computer controlled stimulation of the muscles yields a cybernetic system where a person’s limbs can be tasked to follow a desired trajectory or force profile. Motivation for such a cybernetic system includes advanced rehabilitative outcomes (i.e., neuroplasticity and restoration of function) for individuals with neurological disorders. A challenge to developing these outcomes is that muscle activation dynamics are uncertain and nonlinear, and the dynamics of limb motion also require the coordinated switching among multiple muscle groups. Moreover, artificial stimulation of the muscle is highly inefficient, leading to rapid muscle fatigue, which can limit the therapeutic outcomes. This talk focuses on how perspectives from and advances in robotics / automation / control systems can be used to overcome these challenges. Underlying theories and experimental results for various closed-loop electrical stimulation methods will be described including recent advances in cybernetic cycling where a robotic bicycle is combined with an electrically stimulated person to facilitate various rehabilitative objectives.
Biography: Warren Dixon received his Ph.D. in 2000 from the Department of Electrical and Computer Engineering from Clemson University. He was selected as an Eugene P. Wigner Fellow at Oak Ridge National Laboratory (ORNL). In 2004, he joined the University of Florida in the Mechanical and Aerospace Engineering Department, where he currently holds the Newton C. Ebaugh Professorship. His main research interest has been the development and application of Lyapunov-based control techniques for uncertain nonlinear systems. He has published 3 books, an edited collection, 12 chapters, and over 100 journal and 200 conference papers. His work has been recognized by the 2015 & 2009 American Automatic Control Council (AACC) O. Hugo Schuck (Best Paper) Award, the 2013 Fred Ellersick Award for Best Overall MILCOM Paper, a 2012-2013 University of Florida College of Engineering Doctoral Dissertation Mentoring Award, the 2011 American Society of Mechanical Engineers (ASME) Dynamics Systems and Control Division Outstanding Young Investigator Award, the 2006 IEEE Robotics and Automation Society (RAS) Early Academic Career Award, an NSF CAREER Award (2006-2011), the 2004 Department of Energy Outstanding Mentor Award, and the 2001 ORNL Early Career Award for Engineering Achievement. He is an IEEE Control Systems Society (CSS) Distinguished Lecturer and is an IEEE Fellow for contributions to adaptive control of uncertain nonlinear systems.
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Thor I. Fossen, Norwegian University of Science and Technology, Norway
Title: Nonlinear Observer Design for GNSS- and Camera-Aided Strapdown Inertial Navigation Systems
Abstract: The navigation system is one of the key components when designing modern guidance, navigation and control (GNC) systems. Navigation is usually defined as the task of determining an object’s position, velocity and attitude (PVA) based on various types of information. For decades the Kalman filter (KF), and nonlinear extensions thereof, has been used to provide integrated navigation solutions based on different types of measurements. One disadvantage of the KF is its relatively high computational complexity, with the number of internal states growing quadratically with the number of actual estimates. Another disadvantage is that the KF is developed for linear systems and stability can be difficult or impossible to prove for nonlinear extensions such as the extended Kalman filter (EKF). Consequently, there is a growing interest in the design of nonlinear observers for strapdown inertial navigation systems (INS), which can provide explicit stability guarantees and reduced computational complexity. In recent years there has been a breakthrough in the development of low-cost inertial measurement units (IMUs) based on micro-electromechanical system (MEMS) technology. The IMU is the key component of a strapdown INS and nonlinear observer theory makes it possible to develop highly effective navigation. Applications are low-cost consumer electronics, cars, navigation systems for autonomous underwater vehicles (AUVs), ships, and unmanned aerial vehicles (UAVs) etc.
In this talk, a globally exponentially stable (GES) observer for attitude and gyro bias estimation is presented. The attitude observer uses gyro measurements and two or more pairs of vector measurements, typically body-fixed acceleration and magnetic field measurements. Velocity estimates from optical flow camera measurements can also be used. The attitude observer avoids the well-known topological obstructions to global stability by not confining the attitude estimate to SO(3), but rather estimating a full rotation matrix with nine degrees of freedom. A quaternion-based representation for effective implementation, which guarantees semiglobal exponential stability, is also presented. Next, a translational motion observer (TMO) for estimation of position and linear velocity is presented. The attitude and TMO observers form a feedback interconnection, which is analyzed using Lyapunov theory. Explicit stability requirements for GES are given. The nonlinear observer can be implemented using IMU, magnetometer and GNSS measurements. Extensions to camera-based navigation are also discussed. Low-cost integrated navigation systems using nonlinear observer theory is an emerging technology for autonomous vehicles operating in uncertain and harsh environments. The presentation focuses on the theory of nonlinear observers, stability properties and experimental validation of the methods using experimental data obtained from fixed-wing UAV experiments.
Biography: Thor I. Fossen is a naval architect and a cyberneticist. He received an MSc degree in Marine Technology in 1987 and a PhD degree in Engineering Cybernetics in 1991 both from the Norwegian University of Science and Technology (NTNU), Trondheim. He has been a Fulbright scholar in flight control at the Department of Aeronautics and Astronautics of the University of Washington, Seattle in 1989/1990 and he was appointed professor of guidance, navigation and control at NTNU at age 30. Fossen has been elected to the Norwegian Academy of Technological Sciences (1998) and elevated to IEEE Fellow (2016). He is teaching mathematical modeling of aircraft, marine craft, unmanned vehicles and control theory. Fossen has authored five textbooks. He is one of the co-founders of the DNV-GL company Marine Cybernetics where he was Vice President R&D in the period 2002-2008. He is currently the co-director of the Centre for Autonomous Marine Operations and Systems (AMOS) at NTNU. Fossen's expertise covers guidance, navigation, nonlinear control theory, unmanned vehicles, autonomous and intelligent systems, hydrodynamics, ship control systems and nonlinear observers for strapdown inertial navigation systems. He received the Automatica Prize Paper Award in 2002 and Arch T. Colwell Merit Award in 2008 at the SAE World Congress.
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Xiaohua Xia, University of Pretoria, South Africa
Title: Control Problems in Building Energy Retrofit and Maintenance Planning
Abstract: This paper presents a series of control problems in prioritizing building energy retrofit and maintenance plans through a review of our studies. The building energy retrofits can be strategically performed on policy level, building energy management level, building energy system level and unit level. Based on existing research efforts, this study casts the optimal building maintenance planing problem into a general control system framework. Unlike traditional control applications, this study argues that the control system framework is also applicable to the building energy management level, which will significantly improve the sustainability of realized energy savings and cost-effectiveness of building energy retrofits. In a general control framework, a number of research problems in the control systems are systematically formulated, namely 1) control system decay dynamics modeling; 2) control system inputs and model uncertainties; 3) control system outputs; 4) control system uncertainties and disturbances; 5) control system algorithm; and 6) grouping and modeling. The proposed control problems bring out the intrinsic relationship of reliability engineering, maintenance engineering and control engineering in the broad directions of energy efficiency and optimization. Investigations into the proposed control problems will contribute to further improvements in the building energy retrofit and maintenance plans than the currently prevailing engineering practice.
Biography: Xiaohua Xia obtained his PhD degree at Beijing University of Aeronautics and Astronautics, Beijing, China, in 1989. He stayed at the University of Stuttgart, Germany, as an Alexander von Humboldt fellow in May 1994 and for two years, followed by two short visits to Ecole Centrale de Nantes, France and National University of Singapore during 1996 and 1997, respectively, both as a post-doctoral fellow. He joined the University of Pretoria, South Africa, since 1998, and became a full professor in 2000. He also held a number of visiting positions, as an invited professor at IRCCYN, Nantes, France, in 2001, 2004 and 2005, as a guest professor at Huazhong University of Science and Technology, China, and as a Cheung Kong chair professor at Wuhan University, China. He is an IEEE fellow, served as the South African IEEE Section/Control Chapter Chair, as the chair of the Technical Committee of Non-linear Systems, as a member of the Technical Board (both of IFAC). He is an A-rated scientist by the National Research Foundation of South Africa, an elected fellow of the South African Academy of Engineering, and an elected member of the Academy of Science of South Africa. He has been an Associate Editor of Automatica, IEEE Transactions on Automatic Control, IEEE Transactions on Circuits and Systems II, and the Specialist Editor (Control) of the SAIEE Africa Research Journal. His research interests include: non-linear feedback control, observer design, time-delay systems, hybrid systems, modelling and control of HIV/AIDS, control and handling of heavy-haul trains and energy modelling and optimisation. He is a registered professional engineering by the Engineering Council of South Africa, and a certified measurement and verification professional by the American Association of Energy Engineers. He is the director of both the Centre of New Energy Systems at the University of Pretoria and the National Hub for the Postgraduate Programme in Energy Efficiency and Demand Side Management. He is an elected board member of measurement and verification council of South Africa (MVCSA) since 2014. He is the founding director of Onga Energy Efficiency and Management Pty Ltd - the first SANAS accredited M&V Company against ISO 17020 and he is invited as a technical assessor for the South African National Accreditation Systems (SANAS) for M&V inspection bodies in South Africa.
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