Abstract
There are time delays not only in natural systems such as electrical systems, biological systems, chemical processes, and social networks, but also in artificial systems such as networks. However, since time-delay systems are infinite dimensional rather than finite dimensional, analytic techniques had hardly handled time-delay systems. This talk will address meaningful numerical techniques for analysis of time delay systems.
In 1999, an integral inequality was introduced that plays a key role in generating the delay-dependent stability condition of time-delay systems in terms of linear matrix inequalities. The integral inequality has two kinds of vectors inside: state-derivative vectors that are a function of the integrant and the other vectors that are not, leading to the construction of a delay-dependent stability condition. This work initiated a new direction in robust control for time delay systems with numerical techniques based on linear matrix inequalities. Whereas the integral inequality lemma played a key role in guiding various delay-dependent criteria for time-delay systems, the Jensen integral inequality had become an alternative as a way of reducing the number of decision variables at the expense of a deterioration in performance. It loosened the integral term of the quadratic quantities directly into the quadratic term of the integral quantities, which lead to a linear combination of positive functions weighted by the inversion of the convex parameters. In 2011, a reciprocal-convexity lower bound lemma was suggested for such a combination, which dramatically increased the performance behavior of the Jensen inequality lemma almost identical to that of the integral inequality lemma, but with much less decision variables. Therefore, this lemma overcame the issue of large computation in the numerical techniques. As an alternative of integral inequalities in 1999, the Jensen integral inequality combined with the reciprocal-convexity lower bound lemma in 2011 became a powerful mathematical tool for stability analysis of time-delay systems. In 2015, a new class of integral inequalities were generated to produce much tighter bounds. When the function is expressed in terms of orthogonal bases, the total energy is the sum of the energy of each component corresponding to the bases. This insight produced multiple-order integral inequalities based on various orthogonal bases.

Biography
PooGyeon Park received the B.S. and M.S. degrees in control and instrumentation engineering from Seoul National University, Seoul, South Korea, in 1988 and 1990, respectively, and the Ph.D degree in electrical engineering from Stanford University, Stanford, CA, USA, in 1995. Since 1996, he has been affiliated with the division of electrical engineering with the Pohang University of Science and Technology (POSTECH), Pohang, South Korea, where he is currently a Professor. His current research interests include robust control for LPV systems, network systems, time delay systems, fuzzy systems, and multi-agent systems. He won 2020 Korea Engineering Award from the President of the Republic of Korea. He is a member of the Korea Academy of Science and Technology, a Nam-go Chair Professor, a fellow of the Institute of Control, Robotics, and Systems, and the Vice-President for Education of the Asian Control Association.

Abstract
The well-known disturbance observer is re-interpreted in terms of singular perturbation theory. The first finding is a necessary and sufficient condition for robust stability under arbitrarily large parametric uncertainties. This finding in turn yields a way of designing coefficients of Q-filter for robust stability. In addition, it is shown that DOB guarantees not only robust steady-state response but also robust “transient” response (with a slight modification of the structure). The analysis is performed in the state-space, which also easily applies to nonlinear plants or multi-input-multi-output plants.

Biography
Hyungbo Shim received the B.S., M.S., and Ph.D. degrees from Seoul National University, Korea, and held the post-doc position at University of California, Santa Barbara till 2001. He joined Hanyang University, Seoul, in 2002. Since 2003, he has been with Seoul National University, Korea. He served as associate editor for Automatica, IEEE Trans. on Automatic Control, Int. Journal of Robust and Nonlinear Control, and European Journal of Control, and as editor for Int. Journal of Control, Automation, and Systems. He serves for the IFAC World Congress 2026 as the general chair. His research interests include stability analysis of nonlinear systems, observer design, disturbance observer technique, secure control systems, and synchronization for multi-agent systems.

Abstract
This presentation will review the basic concept of the compressed sensing approach to control systems. Compressed sensing has been widely researched in the fields of signal processing, machine learning, and statistics. The core idea in compressed sensing is to use the characteristic of sparsity behind the data. The technique is, for example, group testing, spares regression, and feature extraction. Recently, this idea has been applied to systems and control. In particular, sparse control, also known as maximum hands-off control, has attracted much attention in the field of systems and control. This lecture will show the mathematical formulation of maximum hands-off control as a resource-aware control and its applications to physical distribution systems, multi-drone systems, and thermos active building systems.

Biography
Masaaki Nagahara received a bachelor’s degree in engineering from Kobe University in 1998 and a master’s degree and a Doctoral degree in informatics from Kyoto University in 2000 and 2003, respectively. He is currently a Full Professor at the Graduate School of Advanced Science and Engineering, Hiroshima University. He has been a Visiting Professor at Indian Institute of Technology Bombay since 2017. His research interests include control theory, machine learning, and sparse modeling. He received remarkable international awards: Transition to Practice Award in 2012 and George S. Axelby Outstanding Paper Award in 2018 from the IEEE Control Systems Society. Also, he received many awards from Japanese research societies, such as SICE Young Authors Award in 1999, SICE Best Paper Award in 2012, SICE Best Book Authors Awards in 2016 and 2021, SICE Control Division Research Award (Kimura Award) in 2020, and the Best Tutorial Paper Award from the IEICE Communications Society in 2014. He is a senior member of IEEE, and a member of IEICE, SICE, ISCIE, and RSJ.