The colloquium will take place online in Google Meet. You can email the organizer for a link to the meeting.
Jan C. Willems Center for Systems and Control
World leading research in Systems and Control at the University of Groningen
The colloquium will take place online in Google Meet. You can email the organizer for a link to the meeting.
The colloquium will take place online in Google Meet. You can email the organizer for a link to the meeting.
Title: Kernel-based models for system analysis
Abstract: This talk introduces a computational framework to identify nonlinear input-output operators from data. The goal is to find operators that fit a set of system trajectories while satisfying prior knowledge in the form of integral quadratic constraints. The data fitting algorithm is thus regularized by suitable input-output properties required for system analysis and control design. This biased identification problem is shown to admit the tractable solution of a regularized least squares problem when formulated in a suitable reproducing kernel Hilbert space. The kernel-based framework is a departure from the prevailing state-space framework. It is motivated by fundamental limitations of nonlinear state-space models at combining the fitting requirements of data-based modeling with the input-output requirements of system analysis and physical modeling.
The colloquium will take place online in Google Meet. You can email the organizer for a link to the meeting.
Title: On internal and external notions of string stability
Abstract: String stability is an important concept in the analysis and control of vehicle platoons (“strings”) as it prohibits the amplification of disturbances through the string. However, various – somewhat scattered – notions of string stability exist in the literature, ranging from stability-like properties of an equilibrium (internal) to performance-like properties (external). In this talk I will discuss some very preliminary ideas for linking such internal and external string stability properties by drawing inspiration from dissipativity theory.
The colloquium will take place online in Google Meet. You can email the organizer for a link to the meeting.
In this talk I will present some partial answers, starting from the port-Hamiltonian formulation of physical systems. In particular, I will show how the ‘isothermals’ and ‘adiabatics’ in the classical Carnot cycle for heat engines can be directly generalized to port-Hamiltonian systems endowed with a specific interconnection structure. The talk will be illustrated by a series of characteristic examples; from the gas-piston-damper system of thermodynamics to synchronous generators, DC motors and electromechanical actuators.
References:
A. van der Schaft, D. Jeltsema, Limits to Energy Conversion, IEEE-TAC, 2021
A. van der Schaft, D. Jeltsema, On Energy Conversion in Port-Hamiltonian Systems, 60th CDC, Austin, 2021
Dr. Henk van Waarde has joined the SCO group as Assistant Professor for Data-driven control in January 2022. Henk received his PhD degree (cum laude) in Systems and Control from the University of Groningen in 2020 and was awarded with the 2020 DISC Best PhD Thesis. During his PhD he was a visiting researcher at University of Washington, Seattle, in the lab of Mehran Mesbahi. After that he was a postdoctoral researcher, first at Cambridge University under supervision of Rodolphe Sepulchre, and later at ETH Zürich where he worked with Florian Dörfler. His research interests are in data-driven modeling and control as well as applications to networked systems and neuronal dynamics.
The colloquium will take place online in Google Meet. You can email the organizer for a link to the meeting.
Title: A solution theory for coupled systems of PDEs and switched DAEs
Abstract: A distributional solution framework is developed for systems consisting of linear hyperbolic partial differential equations (PDEs) and switched differential-algebraic equations (DAEs) which are coupled via boundary conditions. The unique solvability is then characterize in terms of a switched delay DAE. The theory is illustrated with an example of electric power lines modeled by the telegraph equations which are coupled via a switching transformer where simulations confirm the predicted impulsive solutions.
The colloquium will take place online in Google Meet. You can email the organizer for a link to the meeting.
Title: Clustering-based model reduction of network systems containing cycle
Abstract: In the model reduction of networked systems, clustering-based methods are able to preserve the network structure and synchronisation properties. However, the selection of clustering that results in a reduced-order model with optimal approximation error remains an open problem. The method of [1] enables identifying two nodes/sub-systems that show similar behaviour and, therefore, choosing two nodes to be clustered and resulting in a good approximation, based on the analysis of the Gramians of the edge dynamics. This method works perfectly on networked systems with tree structures, but the extension to more general graph structures containing cycles is not straightforward. In this colloquium, I will present my ongoing research on solving the problem of finding the best-clustering of networks containing cycles using the concept of Gramians for semi-stable systems [2].
[1] Besselink, Bart, Henrik Sandberg, and Karl H. Johansson. “Clustering-based model reduction of networked passive systems.” IEEE Transactions on Automatic Control 61.10 (2015): 2958-2973.
[2] Cheng, Xiaodong, and Jacquelien MA Scherpen. “Novel Gramians for linear semistable systems.” Automatica 115 (2020): 108911.