Author: webtestdcl

February 28, 2020 – 11:15 AM
TSRB auditorium

Abstract

The problem of Stochastic Optimal Control is ubiquitous in Robotics and Control since it is the fundamental formulation for decision-making under uncertainty. The answer to the problem can be computed by solving an associated Dynamic Programming (DP) problem. Unfortunately, the DP paradigm is also synonymous with the infamous “Curse of Dimensionality (COD),” a phrase coined by the discoverer of the Dynamic Programming paradigm, Richard Bellman, nearly 60 years ago, to capture the fact that the computational complexity of solving a DP problem grows exponentially in the dimension of the state space of the problem.

In this talk, we will introduce a newly discovered paradigm in stochastic optimal control, called “Decoupling,” that allows us to separate the design of the open and closed loops of a stochastic optimal control problem with continuous control space. This Decoupled solution allows us to break the COD inherent in DP problems, while remaining near-optimal, to third order, to the true stochastic control. The implications of the Decoupled design are examined in the context of Model Predictive Control (MPC) and Reinforcement Learning (RL). We shall introduce two algorithms, called the Trajectory Optimized Perturbation Feedback Control (T-PFC), and the Decoupled Data based Control(D2C), for the MPC and RL problems respectively. We shall also examine the consequences of the decoupling principle in partially observed/ belief space planning problems and present the Trajectory optimized Linear Quadratic Gaussian (T-LQG) algorithm.

Biography

Suman Chakravorty obtained his B.Tech in Mechanical Engineering in 1997 from the Indian Institute of Technology, Madras and his PhD in Aerospace Engineering from the University of Michigan, Ann Arbor in 2004. From August 2004- August 2010, he was an Assistant Professor with the Aerospace Engineering Department at Texas A&M University, College Station and since August 2010, he has been an Associate Professor in the department. Dr. Chakravorty’s broad research interests lie in the estimation and control of stochastic dynamical systems with application to autonomous, distributed robotic mapping and planning, and situational awareness problems. He is a member of AIAA, ASME and IEEE. He is an Associate Editor for the ASME Journal on Dynamical Systems, Measurement and Control and the IEEE Robotics and Automation Letters.

February 14, 2020 – 11:15 AM
TSRB auditorium

Abstract

We consider situations in which better informed agents must decide which message to transmit to a decision-making receiver, so as to influence the decision in their favor.

Such scenarios, some versions of which have been considered earlier in Economics under the umbrellas of ‘cheap talk’ and ‘persuasion theory’ have found renewed relevance in a number of cyber-socio-physical contexts, and have interesting connections to both information and game theory.

Starting with the simplest single transmitter-single receiver setup, we present several variants of such strategic information transmission of increasing complexity, in terms of (1) strategic refinement and rationality of the players, (2) information asymmetries and (3) sender network structure, as well as applications.

The nature of equilibrium sending strategies, as well as the sender’s ability to reach an appropriate decision despite deception vary widely depending on these assumptions, thus illustrating the subtlety of these deception games.

Biography

Cedric Langbort is an Associate Professor of Aerospace Engineering at the University of Illinois at Urbana–Champaign (UIUC), where he is also affiliated with the Decision & Control Group at the Coordinated Science Lab (CSL), and the Information Trust Institute. Prior to joining UIUC in 2006, he studied at the Ecole Nationale Superieure de l’Aeronautique et de l’Espace-Supaero in Toulouse (France), the Institut Non-Lineaire in Nice (France), and Cornell University, from which he received the Ph.D. in Theoretical & Applied Mechanics in January 2005. He also spent a year and a half as a postdoctoral scholar in the Center for the Mathematics of Information at Caltech. He works on applications of control, game, and optimization theory to a variety of fields; most recently to “smart infrastructures” problems within the Center for People & Infrastructures which he co-founded and co-directs at CSL. He is a recipient of the NSF CAREER Award, the advisor of an IEEE CDC Best Student Paper Award recipient, and has been an associate editor for OCAM, the journal of Optimal Control Application and Methods, as well as for Systems & Control Letters.

November 22, 2019 – 11:15 AM
TSRB Auditorium

Abstract

A number of problems in machine learning involve sequence-to-sequence transformations, i.e., nonlinear operators that map an input sequence to an output sequence. Traditionally, such input-output maps have been modeled using discrete-time recurrent neural nets. However, there has been a recent shift in sequence-to-sequence modeling from recurrent network architectures to autoregressive convolutional network architectures. These temporal convolutional nets (TCNs) allow for easily parallelizable training and operation, while still achieving competitive performance. In this talk, based on joint work with Joshua Hanson, I will show that TCNs are universal approximators for a large class of causal and time-invariant input-output maps that have approximately finite memory. Specifically, I will present quantitative approximation rates for deep TCNs with rectified linear unit (ReLU) activation functions in terms of the width and depth of the network and the modulus of continuity of the original input-output map. Next, I will show how to apply these results to input-output maps with incrementally stable nonlinear state-space realizations. As an example, I will discuss a class of nonlinear systems of Lur’e type that satisfy a variant of the discrete-time circle criterion.

Biography

Maxim Raginsky received the B.S. and M.S. degrees in 2000 and the Ph.D. degree in 2002 from Northwestern University, all in Electrical Engineering. He has held research positions with Northwestern, the University of Illinois at Urbana-Champaign (where he was a Beckman Foundation Fellow from 2004 to 2007), and Duke University. In 2012, he has returned to the UIUC, where he is currently an Associate Professor with the Department of Electrical and Computer Engineering and the Coordinated Science Laboratory. He also holds a courtesy appointment with the Department of Computer Science.

November 08, 2019 – 11:15 AM
TSRB Auditorium

Abstract

From simple logical constructs to complex deep neural network models, Artificial Intelligence (AI)-agents are increasingly controlling physical/mechanical systems. Self-driving cars, drones, and smart cities are just examples of such systems to name a few. However, regardless of the explosion in the use of AI within a multitude of cyber-physical systems (CPS) domains, the safety, and reliability of these AI-enabled CPS is still an understudied problem. Mathematically based techniques for the specification, development, and verification of software and hardware systems, also known as formal methods, hold the promise to provide appropriate rigorous analysis of the reliability and safety of AI-enabled CPS. In this talk, I will discuss our work on applying formal verification techniques to provide formal verification of the safety of autonomous vehicles controlled by end-to-end machine learning models and the synthesis of certifiable end-to-end neural network architectures.

Biography

Yasser Shoukry is an Assistant Professor in the Department of Electrical Engineering and Computer Science at the University of California, Irvine where he leads the Resilient Cyber-Physical Systems Lab. Before joining UCI, he spent two years as an assistant professor at the University of Maryland, College Park. He received his Ph.D. in Electrical Engineering from the University of California, Los Angeles in 2015. Between September 2015 and July 2017, Yasser was a joint postdoctoral researcher at UC Berkeley, UCLA, and UPenn. His current research focuses on the design and implementation of resilient cyber-physical systems and IoT. His work in this domain was recognized by the NSF CAREER Award, the Best Demo Award from the International Conference on Information Processing in Sensor Networks (IPSN) in 2017, the Best Paper Award from the International Conference on Cyber-Physical Systems (ICCPS) in 2016, and the Distinguished Dissertation Award from UCLA EE department in 2016. In 2015, he led the UCLA/Caltech/CMU team to win the NSF Early Career Investigators (NSF-ECI) research challenge. His team represented the NSF- ECI in the NIST Global Cities Technology Challenge, an initiative designed to advance the deployment of Internet of Things (IoT) technologies within a smart city. He is also the recipient of the 2019 George Corcoran Memorial Award for his contributions to teaching and educational leadership in the field of CPS and IoT.

November 01, 2019 – 11:15 AM
TSRB Auditorium

Abstract

Autonomous systems offer the promise of providing greater safety and access. However, this positive impact will only be achieved if the underlying algorithms that control such systems can be certified to behave robustly. This talk will describe a pair of techniques grounded in infinite dimensional optimization to address this challenge. The first technique, which is called Reachability-based Trajectory Design, constructs a parameterized representation of the forward reachable set, which it then uses in concert with predictions to enable real-time, certified, collision checking. This approach, which is guaranteed to generate not-at-fault behavior, is demonstrated across a variety of different real-world platforms. The second technique, is a polynomial optimization method that allows one to compute globally optimal solutions in real-time in the presence of hundreds of constraints. The utility of this approach is validated on a real-time trajectory design task for an autonomous ground vehicle.

Biography

Ram Vasudevan is an assistant professor in Mechanical Engineering and the Robotics Institute at the University of Michigan. He received a BS in Electrical Engineering and Computer Sciences, an MS degree in Electrical Engineering, and a PhD in Electrical Engineering all from the University of California, Berkeley. He is a recipient of the NSF CAREER Award and the ONR Young Investigator Award. His work has received best paper awards at the IEEE Conference on Robotics and Automation, the ASME Dynamics Systems and Controls Conference, and IEEE OCEANS Conference.

October 25, 2019 – 11:15 AM
TSRB Auditorium

Abstract

In the area of multi-robot systems, an understanding of collaboration has been developed and is showing great promise in real-world applications including self-driving cars, industrial automation, precision agriculture, and disaster response. However, existing multi-robot methods still leave much to be desired. In this talk, I will argue for innovation in several areas of multi-robot coordination that are often seen in real-world applications: (1) intermittent monitoring of slowly-evolving spatiotemporal processes on large scales; (2) robots that interact asymmetrically due to imperfect sensors and interference; (3) robots that collaborate as an informed response to a team objective and the environment; and (4) robots that interact with human experts. Towards this vision, I will first discuss methods we have developed that generate temporal deployment plans for multi-robot teams that balance the cost of deployment with the quality of information gathered about some evolving process of interest. In particular, I will outline a combinatorial optimization approach to this “intermittent deployment” problem, yielding greedy solutions with bounded suboptimality. Next, I will detail recent results in coordinated motion control for robots interacting with sensors exhibiting some limited field of view (FOV), along with experimental results in outdoor environments. Finally, I will outline planning problems we have developed that generate temporal interaction structures for multi-robot teams along with trajectories that complement the efforts of humans experts in a search and rescue domain. Throughout the talk I will show examples of the projects at the Coordination at Scale Lab (CAS Lab) at Virginia Tech that motivate the above methods, and conclude by discussing future directions in the area of multi-robot systems.

Biography

Ryan K. Williams received the B.S. degree in computer engineering from Virginia Polytechnic Institute and State University in 2005, and the Ph.D. degree from the University of Southern California in 2014. He is currently an Assistant Professor in the Electrical and Computer Engineering Department at Virginia Tech where he runs the Laboratory for Coordination at Scale (CAS Lab). His current research interests include control, cooperation, and intelligence in distributed multi-agent systems, topological methods in cooperative phenomena, and distributed algorithms for optimization, estimation, inference, and learning. Williams is a Viterbi Fellowship recipient, has been awarded the NSF CISE Research Initiation Initiative grant for young investigators, is a Junior Faculty Award Recipient at Virginia Tech, is a best multi-robot paper finalist at the 2017 IEEE International Conference on Robotics and Automation, and has been featured by various news outlets, including the L.A. Times.

October 11, 2019 – 11:15 AM
TSRB 523A

Abstract

Low gain feedback refers to a family of stabilizing state feedback gains that are parameterized in a scalar, referred to low gain parameter, and go to zero as the low gain parameter decreases to zero. Low gain feedback was initially proposed to achieve semi- global stabilization of linear systems subject to input saturation, and later found its other applications in the stabilization of nonlinear systems and linear systems with input delays. In this talk, we discuss the concept of low gain feedback, its properties, its design methods and its applications in constrained control, nonlinear stabilization and control of time-delay systems.

Biography

Zongli Lin is the Ferman W. Perry Professor in the School of Engineering and Applied Science and a Professor of Electrical and Computer Engineering at University of Virginia. He received his B.S. degree in mathematics and computer science from Xiamen University, Xiamen, China, in 1983, his Master of Engineering degree in automatic control from Chinese Academy of Space Technology, Beijing, China, in 1989, and his Ph.D. degree in electrical and computer engineering from Washington State University, Pullman, Washington, in 1994. His current research interests include nonlinear control, robust control, time delay systems, and control applications. He was an Associate Editor of the IEEE Transactions on Automatic Control (2001-2003), IEEE/ASME Transactions on Mechatronics (2006-2009) and IEEE Control Systems Magazine (2005-2012). He was elected a member of the Board of Governors of the IEEE Control Systems Society (2008- 2010, 2019-2021) and chaired the IEEE Control Systems Society Technical Committee on Nonlinear Systems and Control (2013-2015). He has served on the operating committees several conferences and was the program chair of the 2018 American Control Conference and a general chair of the 13th and 16th International Symposium on Magnetic Bearings (2012, 2018). He currently serves on the editorial boards of several journals and book series, including Automatica, Systems & Control Letters, Science China Information Sciences, and Springer/Birkhauser book series Control Engineering. He is a Fellow of IEEE, IFAC, and AAAS, the American Association for the Advancement of Science.