CISE Seminar: Thomas Parisini, Imperial College London

Date: April 24, 2026
Time: 3:00pm – 4:00pm
Location: 665 Commonwealth Ave., CDS 1101

Thomas Parisini
Professor
Imperial College London, Aalborg University, & University Trieste

Control for Optimisation: from Centralised to Distributed, from Finite-Dimensional to Infinite-Dimensional

In this tutorial lecture we present some key use-cases of challenging
optimisation problems – centralised, distributed, and infinite-dimensional – in which it is shown that a control theoretic approach can have a considerable impact, especially when robustness is considered. Methodologies and tools such as Lyapunov analysis, ISS stability, small-gain theory, time-scales separation, and passivity are all instrumental to unveil fundamental properties of optimisation methods with a significant potential impact on key application areas such as multi-agent systems and large-scale critical infrastructures.

In the first use-case, we revisit the distributed version of the unconstrained Arrow-Hurwicz-Uzawa primal-dual algorithm, which was introduced in 2010 by J. Wang and N. Elia. Here, by means of a Lyapunov-based analysis, we prove global ISS of the algorithm relative to a closed invariant set composed of optimal equilibria and with respect to perturbations affecting the algorithm’s dynamics. In the absence of perturbations, this result implies linear convergence of the local estimates and Lyapunov stability of the optimal steady state. Moreover, we unveil fundamental connections with the well-known Gradient Tracking algorithm and with distributed integral control.

In the second use-case -distributed minimum sharing – a set of decision-makers compute the minimum of some local quantities of interest in a distributed and decentralized way by exchanging information through a communication network. We propose an adjustable approximate solution which enjoys several properties of crucial importance in applications. Specific application contexts are illustrated first. The analysis shows that the proposed solution has good decentralization properties, and it is scalable in that the number of local variables does not grow with the size or topology of the communication network. Moreover, a global and uniform (both in the initial time and in the initial conditions) asymptotic stability result is provided towards a steady state which can be made arbitrarily close to the sought minimum. Exact asymptotic convergence can be recovered at the price of losing uniformity with respect to the initial time. A real industrial use case is described in the metal industry sector.

Next, we consider the discrete-time Arrow-Hurwicz-Uzawa primal-dual algorithm, also known as the first-order Lagrangian method, for constrained optimisation problems involving a smooth strongly convex cost and smooth convex constraints. We deal with the long-standing open problem of nonlocal asymptotic stability of such an algorithm. It is proved that an optimal equilibrium exists, it is unique, and it is semi-globally exponentially stable. We also show that, in the presence of constraints, global asymptotic stability cannot be established for the considered algorithm; hence, semi-global guarantees are the best achievable in general. The generalisation to the distributed version of the constrained discrete-time Arrow-Hurwicz-Uzawa primal- dual algorithm by a control theoretic approach is also addressed showing that passivity tools are instrumental in this challenging context.

Finally, early preliminary attempts to address infinite-dimensional optimisation problems are presented with their potential application of machine learning without function parametrisation.

Thomas Parisini received the Ph.D. degree in electronic engineering and computer science from the University of Genoa, Italy, in 1993. He was an Associate Professor with Politecnico di Milano, Milano, Italy. He currently holds the Chair of industrial control and is the Head of the Control and Power Research Group, Imperial College London, London, U.K. He also holds a Distinguished Professorship at Aalborg University, Denmark. Since 2001, he has been the Danieli Endowed Chair of automation engineering with the University of Trieste, Trieste, Italy, where from 2009 to 2012, he was the Deputy Rector. In 2023, he held a “Scholar-in-Residence” visiting position with Digital Futures-KTH, Stockholm, Sweden. He has authored or coauthored a research monograph in the Communication and Control Series, Springer Nature, and more than 400 research papers in archival journals, book chapters, and international conference proceedings. Dr. Parisini was the recipient of the Knighthood of the Order of Merit of the Italian Republic for scientific achievements abroad awarded by the Italian President of the Republic in 2023. In 2018 he received the Honorary Doctorate from the University of Aalborg, Denmark and in 2024, the IEEE CSS Transition to Practice Award. Moreover, he was awarded the 2007 IEEE Distinguished Member Award and was co-recipient of the IFAC Best Application Paper Prize of the Journal of Process Control, Elsevier, for the three-year period 2011-2013 and of the 2004 Outstanding Paper Award of IEEE TRANSACTIONS ON NEURAL NETWORKS. In 2016, he was awarded as Principal Investigator with Imperial of the H2020 European Union flagship Teaming Project KIOS Research and Innovation Centre of Excellence led by the University of Cyprus with an overall budget of over 40 million Euros. He was the 2021-2022 President of the IEEE Control Systems Society, and he was the Editor-in-Chief of IEEE TRANSACTIONS ON CONTROL SYSTEMS TECHNOLOGY (2009-2016). He was the Chair of the IEEE CSS Conference Editorial Board (2013-2019). Also, he was the associate editor of several journals including the IEEE TRANSACTIONS ON AUTOMATIC CONTROL and the IEEE TRANSACTIONS ON NEURAL NETWORKS. He is currently an Editor of Automatica and the Editor-in Chief of the European Journal of Control. He was the Program Chair of the 2008 IEEE Conference on Decision and Control and General Co-Chair of the 2013 IEEE Conference on Decision and Control. He is a Fellow of IEEE and IFAC. He chairs the IEEE CSS Awards and serves as a Member of IEEE TAB Periodicals Review and Advisory Committee.

Faculty Host: Christos Cassandras
Student Host: Chae Woo Lim