研究者データベース
有泉 亮ARIIZUMI Ryoアリイズミ リヨウ
| ■所属部署名 | 工学研究院 機械システム工学部門 | |||
| ■職名 | 准教授 | |||
Last Updated :2026/07/29
業績情報
氏名・連絡先
氏名
アリイズミ リヨウ, 有泉 亮, ARIIZUMI Ryoeメールアドレス
ryoariizumi
go.tuat.ac.jp
主たる所属・職名
工学研究院 機械システム工学部門, 准教授
経歴
学歴
学位
科学研究費助成事業
- 基盤研究（B）
可変環境への適応と改変を利用したヘビ型ロボットの超冗長制御
自 2024年, 至 2024年 - 基盤研究（B）
可変環境への適応と改変を利用したヘビ型ロボットの超冗長制御
自 2023年, 至 2023年 - 基盤研究(C)
受動性を活用したロボットの強化学習とそのためのデータ駆動モデル構築
自 2022年, 至 2024年 - 基盤研究(B)
物理的事前知識を活用するロボットの強化学習
自 2025年, 至 2028年 - 基盤研究（B）
ヘビ型ロボットによる作業の体系化と大出力化
自 2025年, 至 2025年
論文
- Special Issue on Robotics and Mechatronics Technology for Snake-Like and Hyper-Redundant Robots
Tanaka, Motoyasu; Kamegawa, Tetsushi; Ariizumi, Ryo
JOURNAL OF ROBOTICS AND MECHATRONICS
FUJI TECHNOLOGY PRESS LTD
2024年12月20日, 研究論文（学術雑誌）, 共同, 36, 6, 0915-3942, DOI(公開)(r-map), 1301, 1301 - Motion Design of a Snake Robot to Move Between Two Adjacent Walls
Ariizumi, Ryo; Mizuno, Hiroto; Sasaki, Hiroki; Asai, Toru; Azuma, Shun-ichi; Tanaka, Motoyasu
JOURNAL OF ROBOTICS AND MECHATRONICS
FUJI TECHNOLOGY PRESS LTD
2024年12月20日, 研究論文（学術雑誌）, 共同, 36, 6, 0915-3942, DOI(公開)(r-map), 1357, 1368 - Default detection in demand response based on block-sparse structure
Xu, Fangyuan; Azuma, Shun-ichi; Kobayashi, Koichi; Yamaguchi, Nobuyuki; Ariizumi, Ryo; Asai, Toru
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS
ELSEVIER SCI LTD
Demand response (DR) is the change in electric consumption by prompting consumers to change their normal consumption patterns in response to financial incentives. In various forms of DR, the contract-based DR is a framework to achieve a certain reduction by the contract with individual participants for their reduction. However, in practice, it is inevitable to encounter a default, implying that some of the participants fail contracted reduction owing to an unexpected event. This study develops a method to detect defaulting participants in contract-based DR. The method iterates two steps: estimating the most suspicious participant and inspecting its smart meter. By utilizing block-sparse structures in the detection problem, it can exactly determine the defaulting participants with a small number of inspections. The performance is evaluated by simulation, which indicates that our method has much higher performance than the conventional method in the sense that the number of inspections approximately 96.8% fewer than that of the conventional one.
2024年11月, 研究論文（学術雑誌）, 共同, 162, 0142-0615, DOI(公開)(r-map) - The Dynamical Model and the Slithering Controller of Continuous Snakelike Robot on Smooth Surface
Harada, Koki; Ariizumi, Ryo; Asai, Toru; Azuma, Shun-ichi
INTERNATIONAL JOURNAL OF CONTROL AUTOMATION AND SYSTEMS
INST CONTROL ROBOTICS & SYSTEMS, KOREAN INST ELECTRICAL ENGINEERS
This paper introduces a new dynamical model for a continuous snake-like robot and a controller yielding slithering motion on a smooth curved surface. Smooth curve models are common tools in studies on snake-like robots, however, the application of those models is limited to cases without sideslips. Our new model can deal with locomotion with sideslips on curved surfaces. Moreover, the numerical simulation of climbing up the surface of a cylinder based on our model reveals the important role of the tangential friction of the body, which was underestimated by previous studies. The result illuminates the trade-off relation between the energy efficiency and the reachability of the snake-like robots.
2024年10月, 研究論文（学術雑誌）, 共同, 22, 10, 1598-6446, DOI(公開)(r-map), 3133, 3146 - Extremum Seeking Control of Hopping Rover
Shuntaro Takekuma, Shun-Ichi Azuma, Ryo Ariizumi and Toru Asai
Proceedings of the 8th International Symposium on Swarm Behavior and Bio-Inspired Robotics
2024年09月20日, 研究論文（国際会議プロシーディングス）, 共同, 2433-5096, 217, 220 - Simultaneous Optimization of Discrete and Continuous Parameters Defining a Robot Controller
Takato Ishii, Ryo Ariizumi and Fumitoshi Matsuno
Proceedings of the 8th International Symposium on Swarm Behavior and Bio-Inspired Robotics
2024年09月17日, 研究論文（国際会議プロシーディングス）, 共同, 2433-5096, 75, 81 - Path-Following Control of a Snake Robot with Multiple Passive Joints
R. Ariizumi, K. Sakakibara, T. Asai, and S. Azuma
International Journal of Control, Automation and Systems
INST CONTROL ROBOTICS & SYSTEMS, KOREAN INST ELECTRICAL ENGINEERS
A snake robot should be robust to actuator failures because it has more actuators than required for locomotion. However, controlling a snake robot is problematic if some of the joints become passive because of problems in power supply lines. In a recent study, we proposed a controller to achieve path-following in cases where one of the joints is passive. However, the controller applies only to cases with a single passive joint. With two or more passive joints, it cannot be applied even if sufficient active joints remain. This paper considers the path-following control of a snake robot with passive joints by extending our previous study (the single passive joint case). The validity of the method is verified by numerical simulation.
2024年08月, 研究論文（学術雑誌）, 共同, 22, 8, 1598-6446, DOI(公開)(r-map) - Networks of Classical Conditioning Gates and Their Learning
S. Azuma, D. Takakura, R. Ariizumi, and T. Asai
New Generation Computing
SPRINGER
A research project on chemical AI, called the Molecular Cybernetics Project, was launched in Japan in 2021 with the goal of creating a molecular machine that can learn a type of conditioned reflex through the process of classical conditioning. In this project, we have developed a learning method for the network of such learning molecular machines, which is reported in this paper. First, as a model of a learning molecular machine, we formulate a logic gate that can learn conditioned reflex and introduce the network of the logic gates. Then we derive a key principle for learning, called the flipping principle, by which we present a learning algorithm for the network to realize a desired function.
2024年06月, 研究論文（学術雑誌）, 共同, 42, 2, 0288-3635, DOI(公開)(r-map), 203, 216 - Data Informativity for Distributed Positive Stabilization
T. Iwata, S. Azuma, R. Ariizumi, and T. Asai
IEEE Control Systems Letters
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
2024年05月22日, 研究論文（学術雑誌）, 共同, 8, DOI(公開)(r-map), 826, 831 - Data-driven Estimation of the Algebraic Riccati Equation for the Discrete-Time Inverse Linear Quadratic Regulator Problem
S. Sugiura, R. Ariizumi, M. Tanemura, T. Asai, and S. Azuma
Discover Applied Sciences
SPRINGER
2024年05月20日, 研究論文（学術雑誌）, 共同, 6, 6, DOI(公開)(r-map) - A Small-data Solution to Data-driven Lyapunov Equations: Data Reduction from O(n^2) to O(n)
K. Tsuji, S. Azuma, I. Banno, R. Ariizumi, T. Asai, and J. Imura
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences
When a mathematical model is not available for a dynamical system, it is reasonable to use a data -driven approach for analysis and control of the system. With this motivation, the authors have recently developed a data -driven solution to Lyapunov equations, which uses not the model but the data of several state trajectories of the system. However, the number of state trajectories to uniquely determine the solution is O(n(2)) for the dimension n of the system. This prevents us from applying the method to a case with a large n. Thus, this paper proposes a novel class of data -driven Lyapunov equations, which requires a smaller amount of data. Although the previous method constructs one scalar equation from one state trajectory, the proposed method constructs three scalar equations from any combination of two state trajectories. Based on this idea, we derive data -driven Lyapunov equations such that the number of state trajectories to uniquely determine the solution is O (n) .
2024年05月, 研究論文（学術雑誌）, 共同, E107A, 5, 0916-8508, DOI(公開)(r-map), 806, 812 - Existence of Reservoir with Finite-Dimensional Output for Universal Reservoir Computing
S. Sugiura, R. Ariizumi, T. Asai, and S. Azuma
Scientific Reports
NATURE PORTFOLIO
In this paper, we prove the existence of a reservoir that has a finite-dimensional output and makes the reservoir computing model universal. Reservoir computing is a method for dynamical system approximation that trains the static part of a model but fixes the dynamical part called the reservoir. Hence, reservoir computing has the advantage of training models with a low computational cost. Moreover, fixed reservoirs can be implemented as physical systems. Such reservoirs have attracted attention in terms of computation speed and energy consumption. The universality of a reservoir computing model is its ability to approximate an arbitrary system with arbitrary accuracy. Two sufficient reservoir conditions to make the model universal have been proposed. The first is the combination of fading memory and the separation property. The second is the neighborhood separation property, which we proposed recently. To date, it has been unknown whether a reservoir with a finite-dimensional output can satisfy these conditions. In this study, we prove that no reservoir with a finite-dimensional output satisfies the former condition. By contrast, we propose a single output reservoir that satisfies the latter condition. This implies that, for any dimension, a reservoir making the model universal exists with the output of that specified dimension. These results clarify the practical importance of our proposed conditions.
2024年04月11日, 研究論文（学術雑誌）, 共同, 14, 1, 2045-2322, DOI(公開)(r-map) - Sufficient condition for locally unidentifiable edge weights from any single state trajectory in networked linear systems
M. Yamakawa, T. Asai, R. Ariizumi, and S. Azuma
SICE Journal of Control, Measurement, and System Integration
TAYLOR & FRANCIS LTD
2024年02月17日, 研究論文（学術雑誌）, 共同, 17, 1, 1882-4889, DOI(公開)(r-map), 80, 86 - ポートハミルトン形式によるヘビ型ロボットの関節角経路追従制御に関するロバスト性解析
近藤暖浩，有泉亮，浅井徹，東俊一
システム制御情報学会誌
2024年02月15日, 研究論文（学術雑誌）, 共同, 37, 2, DOI(公開)(r-map), 35, 44 - 未来地図を利用した搬送ロボットの制御―グラフを利用した経路生成―
松高亜樹，東俊一，有泉亮，浅井徹
システム制御情報学会誌
2024年02月15日, 研究論文（学術雑誌）, 共同, 37, 2, DOI(公開)(r-map), 55, 64 - Automatic Temperature Parameter Tuning for Reinforcement Learning Using Path Integral Policy Improvement
Nakano, Hiroyasu; Ariizumi, Ryo; Asai, Toru; Azuma, Shun-Ichi
IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
In this article, we propose a novel variant of path integral policy improvement with covariance matrix adaptation(PI2-CMA), which is a reinforcement learning (RL) algorithm that aims to optimize a parameterized policy for the continuous behavior of robots. PI2-CMA has a hyperparameter called the temperature parameter, and its value is critical for performance; however, little research has been conducted on it and the existing method still contains a tunable parameter, which can be critical to performance. Therefore, tuning by trial and error is necessary in the existing method. Moreover, we show that there is a problem setting that cannot be learned by the existing method. The pro-posed method solves both problems by automatically adjusting the temperature parameter for each update. We confirmed the effectiveness of the proposed method using numerical tests.
2023年09月29日, 研究論文（学術雑誌）, 共同, 2162-237X, DOI(公開)(r-map) - Local Unidentifiability of Edge Weights for Linear Systems with Graph Laplacian
M. Yamakawa, T. Asai, R. Ariizumi, and S. Azuma
Proceedings of the SICE Annual Conference
2023年09月, 研究論文（国際会議プロシーディングス）, 共同, DOI(公開)(r-map) - Data-driven Estimation of Algebraic Riccati Equation for Inverse Linear Quadratic Regulator Problem
S. Sugiura, R. Ariizumi, T. Asai, and S. Azuma
Proceedings of the SICE Annual Conference
2023年09月, 研究論文（国際会議プロシーディングス）, 共同, DOI(公開)(r-map) - Multi-objective Reinforcement Learning with Path Integral Policy Improvement
R. Ariizumi, H. Sago, T. Asai, and S. Azuma
Proceedings of the SICE Annual Conference
2023年09月, 研究論文（国際会議プロシーディングス）, 共同, DOI(公開)(r-map) - Nonessentiality of Reservoir's Fading Memory for Universality of Reservoir Computing
Sugiura, Shuhei; Ariizumi, Ryo; Asai, Toru; Azuma, Shun-Ichi
IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
This article describes a novel sufficient condition concerning approximations with reservoir computing (RC). Recently, RC using a physical system as the reservoir has attracted attention. Because many physical systems are modeled as state-space systems, it is necessary to guarantee the approximations given by reservoirs represented as nonlinear state-space systems. There are two problems with existing approaches: a reservoir must have a property called fading memory and must be represented as a set of maps between input and output signals on the bi-infinite-time (BIT) interval. These two conditions are too strict for reservoirs represented as nonlinear state-space systems as they require the reservoir to have a unique equilibrium state for the zero input. This article proposes an approach that employs operators from right-infinite-time (RIT) inputs to RIT outputs. Furthermore, we develop a novel extension of the Stone-Weierstrass theorem to handle discontinuous functions. To apply the extended theorem, we define functionals corresponding to operators and introduce a metric on the domain of the functionals. The resulting sufficient condition does not require the reservoir to have fading memory or continuity with respect to inputs and time. Therefore, our result guarantees the approximations with very common reservoirs and provides a rationale for physical RC. We present an example of a physical reservoir without fading memory. With the example reservoir, the RC model successfully approximates NARMA10, a benchmark task for time series predictions.
2023年08月16日, 研究論文（学術雑誌）, 共同, 2162-237X, DOI(公開)(r-map) - Data Informativity for Lyapunov Equations
Banno, Ikumi; Azuma, Shun-Ichi; Ariizumi, Ryo; Asai, Toru; Imura, Jun-ichi
IEEE CONTROL SYSTEMS LETTERS
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Recently, the novel framework for data-driven analysis and control, called data informativity , was proposed. This notion represents whether the given data contain sufficient information to solve a problem or not. This letter characterizes the data informativity for Lyapunov equations in the form of AP+PA⊤=−Q . First, we clarify the relationship between the unique solution and an invariant subspace of the matrix A . Second, based on this result, we provide a necessary and sufficient condition for the data informativity, which is characterized by the possibility of the matrix decomposition of Q . Finally, we present a data-driven method for solving the Lyapunov equation.
2023年06月15日, 研究論文（学術雑誌）, 共同, 7, DOI(公開)(r-map) - Simultaneous Optimization of Discrete and Continuous Parameters Defining a Robot Morphology and Controller
Koike, Ryosuke; Ariizumi, Ryo; Matsuno, Fumitoshi
IEEE TRANSACTIONS ON NEURAL NETWORKS AND LEARNING SYSTEMS
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
The morphology and controller design of robots is often a labor-intensive task performed by experienced and intuitive engineers. Automatic robot design using machine learning is attracting increasing attention in the hope that it will reduce the design workload and result in better-performing robots. Most robots are created by joining several rigid parts and then mounting actuators and their controllers. Many studies limit the possible types of rigid parts to a finite set to reduce the computational burden. However, this not only limits the search space, but also prohibits the use of powerful optimization techniques. To find a robot closer to the global optimal design, a method that explores a richer set of robots is desirable. In this article, we propose a novel method to efficiently search for various robot designs. The method combines three different optimization methods with different characteristics. We apply proximal policy optimization (PPO) or soft actor-critic (SAC) as the controller, the REINFORCE algorithm to determine the lengths and other numerical parameters of the rigid parts, and a newly proposed method to determine the number and layout of the rigid parts and joints. Experiments with physical simulations confirm that when this method is used to handle two types of tasks-walking and manipulation-it performs better than simple combinations of existing methods. The source code and videos of our experiments are available online (https://github.com/r-koike/eagent).
2023年05月24日, 研究論文（学術雑誌）, 共同, 2162-237X, DOI(公開)(r-map) - Optimal Movement for SLAM by Hopping Rover
Takekuma, Shuntaro; Azuma, Shun-ichi; Ariizumi, Ryo; Asai, Toru
IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES
IEICE-INST ELECTRONICS INFORMATION COMMUNICATION ENGINEERS
A hopping rover is a robot that can move in low gravity planets by the characteristic motion called the hopping motion. For its autonomous explorations, the so-called SLAM (Simultaneous Localization and Mapping) is a basic function. SLAM is the combination of estimating the position of a robot and creating a map of an unknown environment. Most conventional methods of SLAM are based on odometry to estimate the position of the robot. However, in the case of the hopping rover, the error of odometry becomes considerably large because its hopping motion involves unpredictable bounce on the rough ground on an unexplored planet. Motivated by the above discussion, this paper addresses a problem of finding an optimal movement of the hopping rover for the estimation performance of the SLAM. For the problem, we first set the model of the SLAM system for the hopping rover. The problem is formulated as minimizing the expectation of the estimation error at a pre-specified time with respect to the sequence of control inputs. We show that the optimal input sequence tends to force the final position to be not at the landmark but in front of the landmark, and furthermore, the optimal input sequence is constant on the time interval for optimization.
2023年05月, 研究論文（学術雑誌）, 共同, E106A, 5, 0916-8508, DOI(公開)(r-map), 715, 720 - Path tracking control of a snake robot with a passive joint
Sakakibara, Kazunori; Ariizumi, Ryo; Asai, Toru; Azuma, Shun-ichi
ADVANCED ROBOTICS
TAYLOR & FRANCIS LTD
The highly redundant nature of a snake robot will enable the robot to complete its task even with a passive joint caused by an actuator failure. However, existing control methods cannot be applied to a snake robot with a passive joint. This paper proposes a control law that achieves linear path-following control of a snake robot with a passive joint. The effectiveness of our control method is shown via numerical simulation and experiment.
2023年04月03日, 研究論文（学術雑誌）, 共同, 37, 7, 0169-1864, DOI(公開)(r-map), 447, 457 - Relation between leader-follower consensus control and feedback vertex sets
Sugiyama, Daiki; Azuma, Shun-ichi; Ariizumi, Ryo; Asai, Toru
ADVANCED ROBOTICS
TAYLOR & FRANCIS LTD
Leader-follower consensus control is a kind of consensus control, where some special agents, called the leaders, have relatively high flexibility in changing their states, and the other agents, called the followers, follow the leaders. One of the important issues for leader-follower consensus control is a leader selection problem, i.e. determining leaders to achieve a desired performance. On the other hand, the notion of a feedback vertex set is well-known in graph theory. Feedback vertex sets are known to play an important role in various problems, e.g. deadlock avoidance and sensing node selection of biological networks. Thus, they are expected to be closely related to leader-follower consensus control. However, their relationship has never been studied so far. This paper discloses the relationship between leader selection and feedback vertex sets. We deal with a problem of finding a minimum leader set to achieve the fastest convergence to consensus and show that a solution to the leader selection problem is given by a feedback vertex set.
2023年01月17日, 研究論文（学術雑誌）, 共同, 37, 1-2, 0169-1864, DOI(公開)(r-map), 37, 45 - Sparse event-triggered control of linear systems
Banno, Ikumi; Azuma, Shun-ichi; Ariizumi, Ryo; Asai, Toru
INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL
WILEY
In event-triggered control, a situation where the control input must be sparse often arises. Therefore, in this study, we propose sparse event-triggered control, meaning that the control input is sparse and updated in an event-triggered manner. First, we present a model-based method for sparse event-triggered control of linear systems, where the event condition is defined by a Lyapunov function. The resulting control input is proven to be sparse and the control system is confirmed to be asymptotically stable. Second, we extend it to a data-driven version, where the event condition is adaptively updated from online data on the state trajectory. Finally, we discuss the possibility of extending our framework to two cases of disturbance and nonlinear dynamics.
2023年01月10日, 研究論文（学術雑誌）, 共同, 33, 1, 1049-8923, DOI(公開)(r-map), 134, 158 - Maximum turn-off control for discrete-time linear systems
Iwata, Takumi; Azuma, Shun-ichi; Ariizumi, Ryo; Asai, Toru
INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL
WILEY
We aim to address the problem of finding a control input maximizing the time instants when all control channels take a zero-value (are turned off) while stabilizing the system to zero over a given horizon length. This problem is called the maximum turn-off control problem. To solve it, we reduce the problem into a block-sparse optimization problem with respect to the control input sequence, where the l2/l0$$ {\ell}_2/{\ell}_0 $$ norm of the control input sequence is the objective function that must be minimized. Because the problem is not convex, we introduce a relaxed problem based on the l2/l1$$ {\ell}_2/{\ell}_1 $$ norm, which is a convex function, and characterize the equivalence relation between the original and relaxed problems using the so-called block restricted isometry property (block-RIP). Based on the equivalence, the solution can be obtained by solving the convex relaxed problem. However, the block-RIP is not easy to interpret and verify. Thus, we propose the notion of sparse controllability Gramians, which is an extension of the controllability Gramians, and show that the block-RIP can be interpreted by the eigenvalues of the sparse controllability Gramian. This study presents an easy-to-check condition of the block-RIP. Moreover, the above control framework is extended to a model predictive control scheme. These results are demonstrated using numerical examples.
2023年01月10日, 研究論文（学術雑誌）, 共同, 33, 1, 1049-8923, DOI(公開)(r-map), 23, 34 - 周期的線形時変システムのLMIに基づく安定性解析手法
堺光徳，浅井徹，有泉亮，東俊一
計測自動制御学会論文集
2023年, 研究論文（学術雑誌）, 共同, 59, 1, DOI(公開)(r-map), 10, 18 - Equilibrium Controllability Analysis and Input Design
T. Iwata, S. Azuma, R. Ariizumi, T. Asai, and J. Imura
SICE Journal of Control, Measurement, and System Integration
2023年, 研究論文（学術雑誌）, 共同, 16, 1, DOI(公開)(r-map) - The DXHS Algorithm Is Equivalent to a Passive Internal Model for Sinusoidal Signals
T. Asai, X. Chen, R. Ariizumi, and S. Azuma
SICE Journal of Control, Measurement, and System Integration
2023年, 研究論文（学術雑誌）, 共同, 16, 1, DOI(公開)(r-map), 382, 386 - Consensus Control of Multi-Hopping-Rover Systems: Convergence Analysis
Takekuma, Shuntaro; Azuma, Shun-Ichi; Ariizumi, Ryo; Asai, Toru
IEEE ACCESS
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
A hopping rover is a mobile robot developed for exploring low-gravity planets. The movement is based on hopping motion for moving on rough ground in low gravity. For efficient exploration, it is desirable to construct a cooperative system with multiple rovers. Such a system is called here the multi-hopping-rover systems. This paper addresses a consensus control problem for the multi-hopping-rover systems, where the hopping rovers involve uncertain dynamics caused by hopping motion. By representing the dynamics by a stochastic model and focusing on the dynamics of the disagreement, we present a condition on the control gain so that the system converges to consensus in a mean-square sense. The result is demonstrated by numerical simulation.
2023年, 研究論文（学術雑誌）, 共同, 11, 2169-3536, DOI(公開)(r-map), 36176, 36183 - Performance Limitation of Group Testing in Network Failure Detection
Xu, Fangyuan; Azuma, Shun-Ichi; Ariizumi, Ryo; Asai, Toru
IEEE ACCESS
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
In a network system, there inevitably be a few connection failures at nodes, such as delay. Once a failure occurs, the network administrator must detect failure sources as soon as possible to maintain communication over the network. Group testing is a method for detecting failure nodes in networks using a small number of measurements, provided that the measurement matrix is constructed appropriately. A promising method for constructing measurement matrices is given by the binary correlation matrices. This study analyzes the performance limitation of group testing based on the binary correlation measurement matrix. We derive the upper and lower bounds of the minimum number of measurements needed for network detection. Moreover, we propose a sufficient condition of network topology, under which the failure vertices in the network can be detected with optimal performance, and we also provide a detection scheme with guaranteed exactness for the network. Numerical example indicates that for the network that satisfies the proposed sufficient condition, the administrator can exactly detect the failure vertices with optimal performance by using our proposed detection scheme.
2023年, 研究論文（学術雑誌）, 共同, 11, 2169-3536, DOI(公開)(r-map), 102852, 102859 - Step Climbing Control of Snake Robot with Prismatic Joints
Iguchi, Yuta; Nakajima, Mizuki; Ariizumi, Ryo; Tanaka, Motoyasu
SENSORS
MDPI
The ultimate goal of this research study is to perform continuous rather than sequential movements of prismatic joints for effective motion of a snake robot with prismatic joints in a complex terrain. We present herein a control method for robotic step climbing. This method is composed of two parts: the first involves the shift reference generator that generates the joint motion for climbing a step, and the other is use of the trajectory tracking controller, which generates the joint motion for the head to track the target trajectory. In this method, prismatic joints are divided into those that are directly controlled for climbing a step and those that are represented as redundancies. By directly controlling the link length, it is possible to prevent the trailing part from back motion when climbing a step, and to avoid a singular configuration in the parts represented as redundancies. A snake robot that has rotational and prismatic joints and can move in three-dimensions was developed, and the effectiveness of the proposed method was demonstrated by experiments using this robot. In the experiment, it was confirmed that the proposed method realizes the step climbing, and the link length limitation using the sigmoid function works effectively.
2022年07月, 研究論文（学術雑誌）, 共同, 22, 13, DOI(公開)(r-map) - Path Integral Policy Improvement With Population Adaptation
Yamamoto, Kosuke; Ariizumi, Ryo; Hayakawa, Tomohiro; Matsuno, Fumitoshi
IEEE TRANSACTIONS ON CYBERNETICS
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Path integral policy improvement (PI2) is known to be an efficient reinforcement learning algorithm, particularly, if the target system is a high-dimensional dynamical system. However, PI2, and its existing extensions, have adjustable parameters, on which the efficiency depends significantly. This article proposes an extension of PI2 that adjusts all of the critical parameters automatically. Motion acquisition tasks for three different types of simulated legged robots were performed to test the efficacy of the proposed algorithm. The results show that the proposed method cannot only eliminate the burden on the user to set the parameters appropriately but also improve the optimization performance significantly. For one of the acquired motions, a real robot experiment was conducted to show the validity of the motion.
2022年01月, 研究論文（学術雑誌）, 共同, 52, 1, 2168-2267, DOI(公開)(r-map), 312, 322 - Multi-objective path integral policy improvement for learning robotic motion
Sago, Hayato; Ariizumi, Ryo; Asai, Toru; Azuma, Shun-ichi
ARTIFICIAL LIFE AND ROBOTICS
Springer Science and Business Media LLC
This paper proposes a new multi-objective reinforcement learning (MORL) algorithm for robotics by extending policy improvement with path integral () algorithm. For a robot motion acquisition problem, most existing MORL algorithms are hard to apply, because of the high-dimensional and continuous state and action spaces. However, policy-based algorithms such as can be applied to solve this problem in single-objective cases. Based on the similarity of and evolution strategies (ESs) and the fact that ESs are well-suited for multi-objective optimization, we propose an extension of and some techniques to speed up the learning. The effectiveness is shown via numerical simulations.
2025年05月02日, 研究論文（学術雑誌）, 共同, 30, 3, 1614-7456, DOI(公開)(r-map), 534, 545 - CRAGE and GNN-based AI architecture for autonomous transitions in modular robots
Satonaka, Kenichiro; Nishii, Ryusei; Kinjo, Ryota; Ohashi, Seiichi; Negoro, Tomoya; Takagi, Yuki; Oku, Hiroshi; Tanigaki, Yuki; Harada, Koki; Ariizumi, Ryo; Simomura, Tomohiro; Yang, Guang; Wang, Xixun; Matsuno, Fumitoshi
ARTIFICIAL LIFE AND ROBOTICS
SPRINGER
The Moonshot R&D project, “Self-evolving AI robot system for lunar exploration and human outpost construction,” aims to realize AI modular robots that integrate advanced physical capabilities with self-evolving AI learning. Modular robots face significant challenges in achieving optimal and rapid shape transitions due to the vast number of possible configurations. To tackle this challenge, we first developed a Graph Neural Network (GNN) designed to learn abstract structural features inherent to modular robots—such as functional equivalence and geometric symmetry. To enable effective training of such a GNN, we developed a novel isomorphism determination method called Canonical Robot Adaptive Graph Encode (CRAGE), which converts structural graphs into canonical strings for efficient and consistent comparison. This graph-to-string encoding makes it possible to identify structurally equivalent configurations with high accuracy and speed. Moreover, CRAGE allows for the rapid and scalable generation of high-quality training data for robot structures, isomorphism classification, and deformation path planning—providing essential input for the GNN. Experiments show that CRAGE achieves 100% accuracy in small- to medium-scale structures while reducing processing time by over 90% compared to conventional methods. GNNs trained on CRAGE-generated data accurately predicted Lv2 structural equivalence from Lv1 inputs, achieving up to 100% classification accuracy and demonstrating strong generalization across structural variations. Together, CRAGE and the GNN form a unified framework for fast and scalable transition planning, contributing to the realization of autonomous self-evolving modular robots.
2025年12月10日, 研究論文（学術雑誌）, 共同, 31, 1, DOI(公開)(r-map), 265, 279 - Automatic robot design for fault-tolerant robots
Kikuzumi, Kenta; Ariizumi, Ryo; Matsuno, Fumitoshi
SCIENTIFIC REPORTS
NATURE PORTFOLIO
It is important for legged robots to be tolerant of joint malfunctions, especially when working in extreme environments such as the surface of an extraterrestrial planet. However, it is not easy to guarantee tolerance, which requires either the robot structure and controller to be carefully designed for specific failure situations or prompt detection and diagnosis of the faults followed by quick controller reconfiguration. To solve this problem, this paper proposes a method using the automatic robot design method recently proposed by some of the authors. The core of the automatic robot design is in the method of updating the robot topology. In this paper, we combine two distinct robot topology update methods to make learning more efficient. Using a physical simulator, we simulate a situation in which several randomly selected joints malfunction. The simulation reveals that the proposed method efficiently trains a robot to walk even when some of its joints are malfunctioning without the need to switch the controller. Test results show that the obtained pair of robot structures and controllers perform well in situations not experienced during training.
2025年08月13日, 研究論文（学術雑誌）, 共同, 15, 1, 2045-2322, DOI(公開)(r-map) - Necessary and Sufficient Reservoir Condition for Universal Reservoir Computing
Sugiura, Shuhei; Ariizumi, Ryo; Asai, Toru; Azuma, Shun-ichi
MATHEMATICS
MDPI
We discuss necessary and sufficient conditions for universal approximation using reservoir computing. Reservoir computing is a machine learning method used to train a dynamical system model by tuning only the static part of the model. The universality is the ability of the model to approximate any dynamical system with any precision. In the previous studies, we provided two sufficient conditions for the universality. We employed the universality definition that has been discussed since the earliest studies on reservoir computing. In this present paper, we prove that these two conditions and the universality are equivalent to one another. Using this equivalence, we show that a universal model must have a pathological property that can only be achieved or approached by chaotic reservoirs.
2025年10月28日, 研究論文（学術雑誌）, 共同, 13, 21, DOI(公開)(r-map)
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