Details of a Researcher - Namerikawa, Toru

Papers - Namerikawa, Toru

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Safe Hierarchical Control of CAVs in Mixed Traffic Scenario: A Level-K Reasoning Based Coalitional Game Approach

Y Nakai, T Namerikawa

2025 IEEE Conference on Control Technology and Applications (CCTA), 596-601 596 - 601 2025.08

Research paper (international conference proceedings), Joint Work, Accepted

This study proposes a hierarchical control of CAVs (Connected and Automated Vehicles) in a mixed traffic scenario. Although there have been many studies using CAVs, there are still few studies on mixed traffic in which a HDV (Human Driven Vehicle) and CAVs coexist. Focusing on the merging control of mixed traffic scenario, many studies have fixed the merging point and merging order, which should be able to be determined freely. To address this problem, we propose a 3-layer hierarchical control method. The upper layer uses a coalitional game based on level-K reasoning. The middle layer uses model predictive control. Finally, the lower layer uses control barrier function. The upper layer decides when to merge in an area by considering the behavior of HDV. The middle layer generates trajectories within constraints. The lower layer uses elliptical constraints to follow trajectories under free merging order safely. Each layer operates at a different time step. Simulation verification of highway merging is performed to demonstrate the effectiveness of the proposed method.

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Distributed Averaging Control for Wide-Area Frequency Synchronization in Power Systems under Passivity

H Kang, T Namerikawa

2025 American Control Conference (ACC), 2956-2961 2956 - 2961 2025.07

Research paper (international conference proceedings), Accepted, ISSN 07431619

The frequency synchronization problem of wide-area control from the higher level of networked power systems is considered. We investigate the exponential convergence and robustness of the passivity-based distributed averaging controller used in damping the inter-area oscillations of power networks and coping with the time-varying power demand. A strict composite storage function is constructed that allows us to quantify the exponential convergence rate of the closed-loop system. Furthermore, L<inf>2</inf> gain performance is utilized as a tool to quantify the impact of time-varying power demand on control areas. We simulate the controller performance on a four-area network which is equivalent to the IEEE New England 39-Bus system.

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Resilient formation control in multi-agent systems considering leader failure

T Murakami, T Namerikawa

SICE Journal of Control, Measurement, and System Integration (Taylor & Francis) 18 ( 1 ) 2025.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 1882-4889

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Relationship Between the Number of Agents and Sparse Observability Index

T. Shinohara, T. Namerikawa

IEEE Open Journal of Control Systems (Institute of Electrical and Electronics Engineers) 4 144 - 155 2025.05

Research paper (scientific journal), Joint Work, Accepted, ISSN 2694085X

The state estimation problem in the presence of malicious sensor attacks is commonly referred to as a secure state estimation problem. Central to addressing this problem is the concept of the sparse observability index, defined as the largest integer δ for which the system remains observable after the removal of any δ sensors. This index plays a critical role in quantifying the resilience of the system, as a higher δ enables unique state reconstruction despite the presence of more compromised sensors. In this study, for undirected multi-agent systems consisting of n agents, we analyze the relationship between the number of agents n and the sparse observability index δ for effective secure state estimation. In particular, we consider four typical graph structures: path, cycle, complete, and complete bipartite graphs. Our analysis reveals that δ does not increase monotonically with n, and that resilience is intricately tied to the underlying network structure. Notably, we demonstrate that the system exhibits enhanced resilience when the number of agents n is a prime number, although the specifics of this relationship vary depending on the graph topology.

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Passivity‐Based Distributed Averaging Control for Wide‐Area Frequency Synchronisation with Time‐Varying Power Demand

Heng Kang, Toru Namerikawa

IET Control Theory & Applications (John Wiley and Sons Inc) 19 ( 1 ) 2025.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 17518644

The frequency synchronisation problem of wide-area control from the higher level of networked power systems is considered. We investigate the asymptotic convergence and robustness of the passivity-based distributed averaging control used in damping the inter-area oscillations of power networks and coping with the time-varying power demand. A strict composite storage function is constructed that allows us to quantify the asymptotic convergence rate of the closed-loop system. Furthermore, the power sharing and (Formula presented.) gain performance are utilized as a tool to quantify the impact of time-varying power demand on control areas. We simulate the controller performance on a four-area network which is equivalent to the IEEE New England 39-Bus system.

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Adaptive CBF を用いた CAV の階層型制御

中井優太，滑川徹

計測自動制御学会論文集 (計測制御自動学会) 61 ( 3 ) 166 - 174 2025.03

Research paper (scientific journal), Last author, Accepted

Distributed and Cooperative Exploration for Multiple Targets Using Detection Maps

H Kobayashi, T Namerikawa

Transactions of the Society of Instrument and Control Engineers (計測制御自動学会) 61 ( 3 ) 203 - 210 2025.03

Research paper (scientific journal), Joint Work, Accepted

Consensus Control for Resilient Multi-Agent Systems Considering Leader Failure

Murakami Takuya, Namerikawa Toru

2025 SICE International Symposium on Control Systems, SICE Iscs 2025 (Institute of Electrical and Electronics Engineers Inc.) 38 - 42 2025.03

Research paper (international conference proceedings), Accepted

In this paper, we study a consensus control problem for resilient multi-agent systems considering leader failure. We present cooperative control to solve the formation problem, enabling the agents to maintain relative positions even if any agent, including the leader, malfunctions. To accomplish this goal, we designed an algorithm that implements distributed observers for fault detection to assess each agent's reliability. The algorithm reduces the effect of faults by limiting information exchange with low-reliability agents. Next, we extended the adjacency matrix so that any follower can replace the leader in response to the leader's failure. Finally, we verify the proposed method through simulations.

Optimal Security Investment Problem for Secure State Estimation on Cyber-Physical Systems

Takumi Shinohara, Toru Namerikawa

IEEE Transactions on Automatic Control 70 ( 2 ) 1244 - 1251 2025.02

Research paper (scientific journal), Joint Work, Accepted, ISSN 00189286

In this article, we deal with the optimal security investment problem for secure state estimation on cyber-physical systems. Toward effective secure state estimation, we aim to determine an optimal security investment that maximizes cost-effectiveness between the cost of the countermeasures and the effect of reinforcing the system resilience. Specifically, for each sensor, we decide whether to take costly security-aware action or inexpensive nonsecurity-aware action. In this article, we call the problem the optimal security investment problem, and we show that it is coNP-hard. Therefore, unless P = coNP, it is generally impossible to compute the optimal security investment in polynomial time. However, we also show a positive result that the optimal security investment can be solved in polynomial time if all the eigenvalues of the system matrix have geometric multiplicity 1. This article also presents the effect of improving the system resilience by adopting security-aware actions.

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Passivity‐based event‐triggered frequency control in power system using dynamic pricing

Yasutomo Shibata, Heng Kang, Toru Namerikawa

IET Control Theory & Applications (John Wiley and Sons Inc) 19 ( 1 ) 2025.01

Research paper (scientific journal), Joint Work, Last author, Accepted, ISSN 17518644

The integration of renewable energy resources in modern power systems promotes flexible demand response but poses challenges to power balance and frequency stability due to their intermittent generation. To address this problem, this study deals with the frequency control of power system in the presence of demand responses. The dynamic electricity pricing scheme enabling both demand response participants and suppliers to contribute to the frequency regulation via their own decision-making process is proposed. The main concern in the controller design is the integration of physical and human systems on the same timescale, encompassing controllers based on frequency dynamics and dynamic pricing. Therefore, event-triggered conditions are proposed to decrease the communication frequency while ensuring system stability, leveraging the passivity property of the system. Under the proposed event-triggered conditions, the authors clearly demonstrate the asymptotic stability around the equilibrium point of the entire system. Furthermore, a numerical simulation using a four areas power network system is performed, confirming the effectiveness of the proposed control scheme and the stability of the system.

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Security Measure Implementation for Distributed State Estimation

T Shinohara, T Namerikawa

IFAC-PapersOnLine 58 ( 30 ) 308 - 313 2024.12

Research paper (international conference proceedings), Accepted, ISSN 24058971

Toward the realization of secure and resilient cyber-physical human systems (CPHS), this paper deals with the distributed secure state estimation problem considering security measure implementation for the systems. We present that the implementation enhances the system resilience, which means that the distributed state estimation can be achieved even if more networks are compromised. We also show that the implementation is coNP-hard, but, on the positive side, the implementation can be solved in polynomial time when the system satisfies a certain condition. This paper further provides a distributed secure state estimator exploiting the security implementation.

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Learning-Allocation Dynamics in Coalitional Games with Transferable Utility

A Khaleghi, D Bauso, T Namerikawa

IFAC-PapersOnLine 58 (30), 31-36 58 ( 30 ) 31 - 36 2024.12

Research paper (international conference proceedings), Joint Work, Accepted, ISSN 24058971

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Event-triggered Pricing-based Frequency Control in Power System via Passivity Analysis

Y Shibata, T Namerikawa

2024 IEEE 63rd Conference on Decision and Control (CDC), 5777-5782 5777 - 5782 2024.12

Research paper (international conference proceedings), Accepted, ISSN 07431546

This study addresses the problem of frequency control in a power system with the participation of demand response (DR). The pricing-based controller is applied to the power system so that DR participants and suppliers can contribute to the frequency regulation via electricity price. However, the high frequency of communication between frequency dynamics and pricing-based controllers is thought to be a problem. To address this problem, we derive event-triggered conditions that reduce the communication frequency while maintaining stability based on the passivity property of the system, and the asymptotical stability around the equilibrium point of the overall system is derived under the proposed event-triggered conditions. Furthermore, numerical simulation with simplified power network system is conducted so the effectiveness of the proposed system design and system stability is confirmed.

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Model Predictive Control Algorithm Based on Signal Temporal Logic with Disturbances Guaranteeing Feasibility

A Kuchiki, T Namerikawa

2024 IEEE 100th Vehicular Technology Conference (VTC2024-Fall) 2024.11

Research paper (international conference proceedings), Joint Work, Accepted

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Distributed Multi-Task Assignment for Multi-Agent Systems

Takamizawa Soya, Tsuge Shunsuke, Namerikawa Toru

International Conference on Control Automation and Systems (IEEE Computer Society) SCI24 ( 0 ) 1457 - 1462 2024.10

Research paper (international conference proceedings), Accepted, ISSN 15987833

In this research, we solve the task assignment problem of multiple agents to multiple tasks in a multi-agent system. Regarding the problem of one agent versus multiple tasks, we use the concept of "grouping,"in which each agent seeks a set of tasks that it can handle at once. On the other hand, for the problem of multiple agents versus one task, we use the concept of the "Timetable"with the goal of synchronizing the start time of each agent's task. By combining the two concepts, it is possible to deal with complex assignment problems, such as each agent executing multiple tasks at the same time, or multiple agents executing one task at the same time. Furthermore, we show that this solution can respond if circumstances changes, such as when the number of agents decreases or the number of tasks increases.

Hierarchical Control of CAV Using Adaptive CBF

NAKAI Yuta, NAMERIKAWA Toru

International Conference on Control Automation and Systems (IEEE Computer Society) 471 - 476 2024.10

Research paper (international conference proceedings), Accepted, ISSN 15987833

<p>This research proposes a hierarchical control method using model predictive control and control barrier functions for CAVs (connected and automated vehicles). By using model predictive control for the upper layer and a control barrier function for the lower one, we aim to achieve control with reduced fuel consumption while ensuring safety even in environments where the behavior of the vehicle ahead is unpredictable. In this study, we aim to improve the feasibility of the lower layer by using Adaptive CBF. The upper layer takes preventive safety actions based on predictions of the preceding vehicle's behavior and ensures feasibility by using slack variables. The lower one using Adaptive CBF ensures the safety that is lacking. The effectiveness of the proposed method is demonstrated through simulations, comparing the results with those of previous studies.</p>

Distributed and Cooperative Exploration for Multiple Targets Using Probabilistic Roadmaps

H Kobayashi, T Namerikawa

2024 SICE Festival with Annual Conference (SICE FES), 601-606 601 - 606 2024.08

Research paper (international conference proceedings), Accepted

In this study, we propose a distributed search method for multiple targets in In this study, we propose a distributed search method for multiple targets in a two-dimensional space using HEDAC(Heat Equation Driven Area Coverage). HEDAC has been recently used to control multi-agent systems. In contrast to the conventional centralized HEDAC, this paper proposes a decentralized algorithm that uses probability maps to make it more practical. Specifically, each search agent shares the probability of target detection by its own search as a probability map with other agents, and is controlled along the gradient of the potential field created based on this map, enabling it to conduct its search activities in a distributed and efficient way. The contribution of this paper is to improve the flexibility of conventional search methods by decentralizing them. Finally, we confirm the effectiveness of the proposed method through simulation validation.

On the Equivalence between Prescribed Performance Control and Control Barrier Functions

R Namerikawa, A Wiltz, F Mehdifar, T Namerikawa, DV Dimarogonas

2024 American Control Conference (ACC), 2458-2463 2458 - 2463 2024.07

Research paper (international conference proceedings), Accepted, ISSN 07431619

In this paper, we show that Prescribed Performance Control (PPC) is a model-free Control Barrier Function (CBF)-based control approach. Specifically, we establish that a function utilized in the PPC design is a Time-Varying Reciprocal Control Barrier Function (TVRCBF). We demonstrate that PPC satisfies the same gradient condition that is well-known in the CBF literature, ensuring forward invariance. As a result, the control inputs generated by the PPC law belong to the input set characterized by the TVRCBF. Apart from assuming a certain controllability property, no further knowledge on the system dynamics is required. Our theoretical findings improve the understanding of the relationship between PPC and other CBF-based controllers. The theoretical results are validated through numerical simulations.

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Passivity-short-based system-wide stability with L2 gain and stabilization of heterogeneous power systems

H Kang, T Namerikawa

SICE Journal of Control, Measurement, and System Integration (Taylor & Francis) 17 ( 1 ) 2024.07

Research paper (scientific journal), Joint Work, Accepted, ISSN 1882-4889

The problem of decentralized control for overall system stability has received increasing attention due to heterogeneity in power networks. To address this problem, two passivity indices are introduced to characterize the shortage of nonlinear negative imaginary property and (Formula presented.) stability of the coupling network. In a modular decomposition, novel passivity-short-based conditions in a decentralized manner are investigated to ensure asymptotically stability of the overall system and (Formula presented.) stability of the network simultaneously, which is so-called system-wide stability with (Formula presented.) gain. Furthermore, the local subsystems are equipped with a linear matrix inequality-based controller, implementing decentralized stabilization. A numerical simulation with three heterogeneous bus dynamics is illustrated to demonstrate the effectiveness of the proposed controller design considering load change and measurement errors, offering insights into system robustness.

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外乱存在下での実行可能性を保証した Signal Temporal Logic によるモデル予測制御アルゴリズム

朽木瑛，滑川徹

計測自動制御学会論文集 (計測制御自動学会) 60 ( 7 ) 429 - 438 2024.07

Research paper (scientific journal), Joint Work, Accepted

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