Tokyo Institute of Technology · Engineering
Professor Rui Kato's research lab specializes in the analysis and control of networked and cyber-physical systems under adversarial conditions, with a focus on security and stability. The lab investigates the resilience of nonlinear control systems against Denial-of-Service (DoS) attacks, particularly through quantized feedback and linearization-based approaches under limited data rates. A key research direction involves developing robust control strategies—such as resilient dynamic quantizers and switched system models—that ensure asymptotic and local stability despite packet losses and attack-induced disruptions. The lab also explores cluster synchronization in complex oscillator networks, applying averaging methods and Lyapunov techniques to understand synchronization dynamics in heterogeneous systems.
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Motivated by the recent security issues in cyber-physical systems, this article studies the stabilization problem of networked control systems under denial-of-service (DoS) attacks. In particular, we consider to stabilize a nonlinear system with limited data rate via linearization. We employ a deterministic DoS attack model constrained in terms of attacks’ frequency and duration, allowing us to cover a large class of potential attacks. To achieve asymptotic stabilization, we propose a resilient
We explore a security analysis of nonlinear networked control systems under denial-of-service (DoS) attacks. In particular, we focus on the vulnerability of a linearization approach in a stabilization problem. When linearization-based control is used, DoS attacks can make the state leave the region of attraction. This situation can occur when the initial state lies outside a certain region around the equilibrium, the size of which depends on the strength of the attacks on the network. In this ar
In this paper, we consider the stability analysis of nonlinear networked control systems under Denial-of-Service (DoS) attacks. In particular, we investigate local stabilization through a linearization approach. To formulate the networked control problem subject to such attacks, a switched system representation is employed with the controlled and uncontrolled modes. We provide a characterization of the frequency and duration of DoS attacks under which local stability is guaranteed. Moreover we d
New stability conditions for cluster synchronization of Kuramoto oscillators are presented. Our approach is based on averaging criteria, but the standard method for stability analysis cannot be directly applied due to the lack of uniform continuity with respect to a perturbation parameter. First, we overcome this technical difficulty with the help of nonmonotonic Lyapunov functions. Our extensions of averaging criteria are the key to unify the existing cluster synchronization conditions: (i) the
This paper deals with a quantized feedback stabilization problem of nonlinear networked control systems via linearization. In particular, we study circumstances where the communication channel is interrupted by Denial-of-Service (DoS) attacks and its data rate is limited. We employ a deterministic DoS attack model which constraints the amount of attacks only by their frequency and duration, allowing us to capture a large class of potential attacks. To achieve asymptotic stabilization, we propose
In this paper, we investigate cluster synchronization of heterogeneous Kuramoto oscillators, where multiple synchronized groups of oscillators coexist in a connected network. Motivated by recent studies on brain networks, we provide a framework to analyze stability of the cluster synchronization manifold via timescale separation. A condition known as almost equitable partitions is employed to characterize an invariant manifold of the Kuramoto dynamics. Relying on averaging methods, we show that
In this letter, we develop a framework for estimating the Hausdorff dimension of a compact invariant set for both autonomous and interconnected systems. We first generalize Smith’s method for Hausdorff dimension estimates by using variable metrics in linear matrix inequalities. Then, we study open systems with a characterization similar to the differential dissipativity theory. For linear time-invariant systems, we show that our characterization can be considered as a pure input/output property.
Motivated by complex and diverse dynamics in engineering and nature, this paper considers Hausdorff dimension estimates for compact invariant sets of dynamical systems. Our aim is to develop a framework of dimension analysis as an extension of Lyapunov's stability theory as well as Willems’ dissipativity theory. In particular, we extend the existing result by Smith involving Lyapunov inequalities for Hausdorff dimension estimates by employing state-dependent metrics. The obtained result is then
The equivalence between local and global characteristics of Lur'e systems is investigated. Historically, such problems date back to Vyshnegradskii's conjecture on Watt governors and Eden's conjecture on Lorenz attractors. In the present paper, we develop a unified framework for stability and dimension analyses. This is motivated by the recent works on hidden oscillations and their relations with absolute stability theory. We combine an energy perspective in Lyapunov analysis and a linearization
Incremental stability has become increasingly common in the context of nonlinear control. However, there is a lack of understanding of the difference between several notions of incremental stability. The objective of this paper is to show that the notion of incremental global asymptotic stability is very similar to that of incremental global exponential stability. In particular, nonexponential relaxation of the convergence rate appears only “locally” but not “globally.” Some examples are provide
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