Special issue on System Theory and Delay in honor of Vladimir Kharitonov

This special issue on “System Theory and Delay” is dedicated to Vladimir Kharitonov the occasion of his 70th birthday, in recognition academic leadership this field research. His work systems with delays (a topic that has captured interest since early years research) reached maturity well-known contributions Lyapunov–Krasovskii functionals, delay Lyapunov matrices, prediction-based control. also obtained ground-breaking results robustness polynomial/multivariable polynomial analysis, particularly theorem bears name. We invite reader discover journey scientific research at highest level excellence. In first paper issue, Alexey Egorov describes Vladimir's major Mathematical Systems Theory. Beyond their nature, shine by elegance simplicity, resulting from rigor, hard work, consistency, patience, discipline, indeed a rock-solid preparation St. Petersburg University (former Leningrad University). writings are characterized sobriety, one could even say austerity today's standards, but believes should speak for themselves. Also, outstanding teaching capacity, clarity exposition, patience toward audience, witnessed those who have followed courses or conferences where everything seems flow easily, earned respect admiration colleagues students. Last not least, had privilege spend time know sharp mind, pragmatism, wisdom, subtle sense humor. The content organized three directions: papers line exposed monography “Time-Delay Systems: Functionals Matrices,” fundamental issues theory, finally, new direction studies. thank all authors contributing sharing ideas community us. Among them university classmates, graduate students, occasional frequent collaborators, fellow researchers. Contributions linear continuation work: Aliseyko studies continuous dependence matrices perturbations systems. It shows can compute matrix arbitrary precision any system satisfying condition. second contribution, Gilberto Ochoa Marco Antonio Gomez, integral equations concentrated distributed delay. it possible use time-domain tools instead usual frequency domain approach determine critical parameters delays. following Reynaldo Ortiz, Egorov, Sabine Mondié continue development stability criteria expressed exclusively terms matrix, presentation necessary sufficient conditions equations. Next, Daniel Melchor Aguilar Hector Arismendi Valle introduce functionals multiple exponential estimates solutions. last part, Carlos Cuvas, Omar Santos, Patricio Ordaz, Liliam Rodríguez complete type approximate Bellman functional context suboptimal control design neutral Experimental presented. Fundamental theory: paper, Tamas Balogh, Islam Boussaada, Insperger, Silviu Niculescu study γ-stabilization time-invariant input/output via multiplicity-induced-dominancy-based controller present stabilizability case open-loop real rooted plants. other group, Rasvan discusses notion fragile differential marginally stable difference operator, arising several engineering applications. New directions studies: Irina Alexandrova Zhabko construct time-delay part homogeneous right-hand side degree greater than one. They independent when operator delay-free robust conditions. Alexander Aleksandrov, Natalya Andriyanova, Denis Efimov compare switched Persidskii aid Lyapunov–Razumikhin functions Lyapunov-Krasovskii functionals. discuss an application mechanical Xiang Xu, Lu Liu, Miroslav Krstic, Gang Feng apply backstepping unbounded predictor feedback method strict-feedback infinite-delayed integrator prove closed-loop system. Finally, Deesh Dileep, Christophe Fiter, Laurentiu Hetel, Wim Michiels analyze large-scale networks static asynchronous aperiodic sampled-data controllers. Here, topology may be time-varying switching. hope readers will find great insights into challenging topics further issue. As final comments, congratulations well-deserved 2021 IFAC Lifetime Achievement Awards Time-Delay recently received your pioneering analysis Thank you being inspiring, creative, passionate, allowing us walk our way as colleagues, wish best come.