Ichiro Nishizaki’s research while affiliated with Hiroshima University and other places

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Publications (287)


Integrated Optimization Method for Task Allocation and Hierarchical Reinforcement Learning in Cargo Transport Robots荷物運搬ロボットのためのタスク割り当てと階層型強化学習を用いた統合型最適化手法
  • Article

March 2025

IEEJ Transactions on Electronics Information and Systems

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Ryuya Furukawa

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Shinya Sekizaki

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Ichiro Nishizaki

This paper focuses on the development of learning methods for achieving effective collaborative transportation by multiple robots in a warehouse environment. In large-scale and complex environments, it is necessary for agents to undergo numerous iterations of learning, such as reinforcement learning, to make appropriate behavioral choices. Traditional multi-agent methods like MADDPG (Multi-Agent Deep Deterministic Policy Gradient) and QMIX face the issue of requiring extensive computation time for environmental exploration. Therefore, this paper proposes a two-stage learning procedure that separates overall optimization, including the formulation of general task execution procedures, from individual optimization based on local situation assessments. Additionally, the effectiveness of the proposed method is demonstrated through simulation system analysis adapted to the target environment.


Distribution System Reconfiguration by an Evolutionary Algorithm using Constraint-Guided Dominance and Archive-Based Individual Preservation Strategy制約指向の支配とアーカイブに基づく進化型アルゴリズムによる配電系統再構成

December 2024

IEEJ Transactions on Power and Energy

Shinya Sekizaki

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Shuya Sato

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Takamichi Kawakami

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[...]

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Kazuhisa Hikoyama

When a constraint violation occurs due to adding a new load to distribution systems, it can be resolved by reconfiguring the distribution systems by changing the states of switches and/or by minimum necessary investment. However, it is difficult to reconfigure the distribution system while satisfying the constraints made more severe by the new load installation. To find distribution system candidates that satisfy the severe constraints, this paper proposes a constrained evolutionary multi-objective optimization algorithm (CMOEA). The proposed CMOEA utilizes a constraint-guided dominance-based and archive-based individual preservation strategy, and it efficiently finds distribution system candidates that satisfy the severe constraints. Furthermore, the proposed CMOEA achieves equalization of the number of sections, minimization of the number of remote/manual switch replacements, and suppression of the upgraded length of distribution lines. The effectiveness of the proposed CMOEA is verified by case studies using a large-scale distribution system model equipped with many manual and remote switches.








Figure 3. Enlarged input-output data set.
Result of technological coefficient model.
Concordance rates of production and transportation.
Purchase amounts of resources.
Differences and ratios on purchase amounts of resources.

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Data Envelopment Analysis Approaches for Multiperiod Two-Level Production and Distribution Planning Problems
  • Article
  • Full-text available

October 2023

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23 Reads

This paper deals with two-level production and distribution planning problems in supply chain management where the leader is a distributor and the follower is a manufacturer. Assuming that the distributor can observe the input–output data in the production process, we formulated the data envelopment analysis (DEA) production problem corresponding to the production planning problem of the manufacturer. This paper proposes a novel data envelopment analysis (DEA) approach to solve a challenging multiperiod two-level production and distribution planning problem in supply chain management. The innovative idea behind the proposed approach is to allow the distributor to observe the input–output data regarding the production activities of the manufacturer, even if the distributor cannot fully comprehend all parameters of the manufacturer’s production cost minimization problem. This approach addresses the challenge of uncertain demands by employing a two-stage model with simple recourse and considering the usage of the input–output data. The paper demonstrates the validity of the proposed DEA approaches through computational experiments and discusses the accuracy, reliability, and importance of the input–output data. The proposed approach provides a practical and effective solution to the multiperiod two-level production and distribution planning problem in supply chain management, and can help decision-makers improve the efficiency and effectiveness of their operations. The innovative idea of allowing the distributor to observe the input–output data about the production activities of the manufacturer is a significant contribution to the field of supply chain management and has the potential to advance the state of the art in this area.

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Citations (30)


... Nishizaki et al. [19] addressed two-stage stochastic linear production planning with partial cooperation, involving resource pooling, technology transfer, and product transshipment. Manufacturers determine production levels individually in the first stage, and then collaborate to produce products using pooled resources in the second stage. ...

Reference:

A Review of Game Theory Models to Support Production Planning, Scheduling, Cloud Manufacturing and Sustainable Production Systems
A two-stage linear production planning model with partial cooperation under stochastic demands

Annals of Operations Research

... The shared energy storage takes advantage of its scale, the spatiotemporal complementarity of different users' energy storage needs, and time-sharing multiplexing to effectively improve the flexibility and economy of energy storage (Sekizaki et al., 2023). Xie et al. (2022b) proposed a method of applying shared energy storage on the power generation side to improve the flexibility and economy of energy storage resources in each wind farm through the sharing of energy storage. ...

Cooperative voltage management by demand resources and fair payoff allocation for distribution systems
  • Citing Article
  • February 2023

International Journal of Electrical Power & Energy Systems

... Figure 2 illustrates the proposed hierarchical framework with production control at the upper level and distribution planning at the lower level. Notably, our proposed hierarchical framework differs from the conventional bi-level optimisation structure (Nishizaki et al. 2022;Zhao et al. 2023), nor the integrated learning and optimisation problem . In those approaches, the lower-level problem is typically treated as an embedded optimisation problem for the upper-level agent. ...

Data envelopment analysis approaches for two-level production and distribution planning problems
  • Citing Article
  • August 2021

European Journal of Operational Research

... The key advantage of the microservice design is its flexibility to scale and independent modification of functionality. The data analytics platform embedded in the system features two main processes: artificial neural networks (ANNs) [9,10] and particle swarm optimization (PSO) [11,12]. The ANNs serve for parameter predictions by analyzing ambient conditions, the air conditioner's usage behavior, and the air conditioner's specific performance data. ...

Improvement of Particle Swarm Optimization Focusing on Diversity of the Particle Swarm
  • Citing Conference Paper
  • October 2020

... In Sekizaki et al. (2021) propose a novel methodology to tackle a many-objective engineering problem in the area of network reconfiguration of an electric distribution system. The challenge in the application considered is to determine how best to downsize equipment (distribution lines) such that costs are reduced while feasibility of the network reconfigurations (due to maintenance and/or replacement of distribution lines) is guaranteed. ...

Distribution line downsizing based on a set of non-dominated solutions for a network reconfiguration problem of an electric distribution system with many objectives

Optimization and Engineering

... The identification of the language of a speech is often done by selecting and analyzing a piece of this speech as reported in [8] and [18]. As reported in [11]- [13] and [19], this identification may be done by a classification algorithm based on the automatic learning of a "deep neural network" trained using a multi-language speeches dataset recorded for several speakers. ...

Feature extraction and Classification of Learners using Multi-Context Recurrent Neural Networks
  • Citing Conference Paper
  • November 2019

... Some examples of evolutionary computing models that are often used and can still be developed include Genetic algorithm, particle swarm optimization, ant colony optimization, and bee algorithm (Abidin, 2018). (Hayashida et al., 2019) The 0-1 multidimensional Knapsack problem is a combinatorial problem of selecting items to be stored in a place with capacity constraints. The selection of a small number of items is very easy to do manually, but if the number of items is large and must meet several capacity constraints, it will make a lot of combinatorial choices and difficult to do manually. ...

Improvement of Two-swarm Cooperative Particle Swarm Optimization Using Immune Algorithms and Swarm Clustering
  • Citing Conference Paper
  • November 2019

... Note that the five objectives (4)-(8) include discrete values, i.e., (5) (8). To avoid the numerical instability and find extreme points due to the discrete objective values, we employ an adaptive normalization proposed in our previous research (Sekizaki et al. 2019). ...

A many‐objective evolutionary algorithm incorporating decision maker's preference and its application to management of the electricity distribution network
  • Citing Article
  • July 2019

Journal of Multi-Criteria Decision Analysis

... Thus, these can be an effective means of improving the resilience of power grids. The performance of the digital controller for the SSI under development has been verified using hardware-in-the-loop simulations [9] and demonstration experiments while connected to the grid, along with the independent operation of single-phase microgrids [8,10,11]. The grid stabilization effect is the most important factor to consider when evaluating GFM inverters, and previous research has evaluated the effect of the output current phase of the GFM inverter on the critical fault clearing time in the event of a grid fault [12], along with the deterioration of the transient stability due to a P-f droop controller [13]. ...

Proposal of a single‐phase synchronous inverter with noninterference performance for power system stability enhancement and emergent microgrid operation

Electrical Engineering in Japan