• 한국정보과학회논문지:정보통신
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• 제36권3호
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• pp.212-221
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• 2009

본 논문에서는 GPS가 없는 일반적인 Wireless Sensor Networks(WSNs)상에서 상대적 위치정보를 이용하여 지리적으로 고른 clutter를 구성하고, sensor와 BS사이의 거리를 고려하여 cluster head의 선출빈도를 조절하는 새로운 centralized clustering algorithm "RLCA : Relative Location based Clustering Algorithm for Wireless Sensor Networks"를 제안하고, RLCA의 에너지 소비 효율성이 LEACH에 비해 높다는 것을 실험적으로 보인다.

• Journal of Electrical Engineering and Technology
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• 제5권3호
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• pp.353-362
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• 2010

This paper presents a centralized control algorithm for power system performance in the Korean power system using Flexible AC Transmission Systems (FACTS) devices. The algorithm is applied to the Korean power system throughout the metropolitan area in order to alleviate inherent stability problems, especially concerns with voltage stability. Generally, control strategies are divided into local and centralized control. This paper is concerned with a centralized control strategy in terms of the global system. In this research, input data of the proposed algorithm and network data are obtained from the SCADA/EMS system. Using the full system model, the centralized controller monitors the system condition and decides the operating point according to the control objectives that are, in turn, dependent on system conditions. To overcome voltage collapse problems, load-shedding is currently applied in the Korean power system. In this study, the application of the coordination between FACTS and switch capacitor (SC) can restore the solvability without load shedding or guarantee the FV margin when the margin is insufficient. Optimal Power Flow (OPF) algorithm, for which the objective function is loss minimization, is used in a stable case. The results illustrate examples of the proposed algorithm using SCADA/EMS data of the Korean power system in 2007.

• 한국산업정보학회논문지
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• 제19권4호
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• pp.87-104
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• 2014

본 연구에서는 지역적으로 집중화된 역물류네트워크(Regionally centralized multistage reverse logistics network: cmRL)와 지역적으로 분산회된 역물류네트워크(Regionally decentralized multistage reverse logistics network: dmRL)를 제안하고 있다. cmRL과 dmRL 각각은 고려되는 영역 전체와 지역적으로 분산된 세부영역에서의 RL 네트워크로 구성된다. 이들은 혼합정수계획법(Mixed integer programming: MIP) 모델로 공식화되며, 유전알고리즘(Genetic algorithm: GA)을 통해 해를 구하게 된다. 사례연구에서는 두 가지 형태의 RL네트워크를 제시하며 다양한 수행도 척도를 사용하여 cmRL과 dmRL의 효율성을 비교분석하였다. 분석결과 cmRL이 dmRL 보다 더 우수한 수행도를 나타내었다.

• Smart Structures and Systems
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• 제11권2호
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• pp.163-183
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• 2013

Control systems have been greatly studied in recent years and can be classified as: passive, active, semi-active or hybrid systems. Most forms of control systems have been applied in a centralized manner where all the information is sent to a central node where control the algorithm is then calculated. One of the possible problems of centralized control is the difficulty to scale its application. In this paper, a completely decentralized control algorithm is analytically implemented. The algorithm considers that each of the control systems makes the best decision based solely on the information collected at its location. Semi-active control is used in preference to active control because it has minimal energy consumption, little to no possibility of destabilization, a reduction in the possibility of data saturation, and a reduction in the response time in comparison to centralized control.

• Journal of Information Processing Systems
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• 제19권1호
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• pp.17-32
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• 2023

Centralized hierarchical routing protocols are often used to solve the problems of uneven energy consumption and short network life in wireless sensor networks (WSNs). Clustering and cluster head election have become the focuses of WSNs. In this paper, an energy balanced clustering routing algorithm optimized by sine cosine algorithm (SCA) is proposed. Firstly, optimal cluster head number per round is determined according to surviving node, and the candidate cluster head set is formed by selecting high-energy node. Secondly, a random population with a certain scale is constructed to represent a group of cluster head selection scheme, and fitness function is designed according to inter-cluster distance. Thirdly, the SCA algorithm is improved by using monotone decreasing convex function, and then a certain number of iterations are carried out to select a group of individuals with the minimum fitness function value. From simulation experiments, the process from the first death node to 80% only needs about 30 rounds. This improved algorithm balances the energy consumption among nodes and avoids premature death of some nodes. And it greatly improves the energy utilization and extends the effective life of the whole network.

• 한국측량학회지
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• 제37권5호
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• pp.367-377
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• 2019

As an alternative navigation system for the non-GNSS (Global Navigation Satellite System) environment, a new type of DBRN (DataBase Referenced Navigation) which applies both gravity gradient and terrain, and combines filter-based algorithm with profile matching was suggested. To improve the stability of the performance compared to the previous study, both centralized and decentralized EKF (Extended Kalman Filter) were constructed based on gravity gradient and terrain data, and one of filters was selected in a timely manner. Then, the final position of a moving vehicle was determined by combining a position from the filter with the one from a profile matching. In the simulation test, it was found that the overall performance was improved to the 19.957m by combining centralized and decentralized EKF compared to the centralized EKF that of 20.779m. Especially, the divergence of centralized EKF in two trajectories located in the plain area disappeared. In addition, the average horizontal error decreased to the 16.704m by re-determining the final position using both filter-based and profile matching solutions. Of course, not all trajectories generated improved performance but there is not a large difference in terms of their horizontal errors. Among nine trajectories, eights show smaller than 20m and only one has 21.654m error. Thus, it would be concluded that the endemic problem of performance inconsistency in the single geophysical DB or algorithm-based DBRN was resolved because the combination of geophysical data and algorithms determined the position with a consistent level of error.

• 한국산학기술학회논문지
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• 제21권2호
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• pp.8-18
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• 2020

본 연구에서는 기존의 Harmony Search(HS)의 성능을 강화한 Exponential Bandwidth Harmony Search with Centralized Global Search(EBHS-CGS)를 개발하였다. EBHS-CGS는 HS의 성능 강화를 위해 총 두 가지 방법을 추가하였다. 첫 번째 방법은 지역탐색을 강화하기 위한 Bandwidth(bw) 개량방안이다. 이 방법은 기존 bw를 지수형태의 bw로 대체하여 적용함으로써 반복시산이 진행되면서 bw값을 줄인다. 이러한 형태의 bw는 정밀한 지역탐색을 가능하고, 이를 통해 알고리즘은 더욱 정밀한 값을 구할 수 있다. 두 번째 방법은 효과적인 전역탐색을 위한 탐색범위 축소이다. 이 방법은 Harmony Memory(HM) 내에서 가장 좋은 결정변수를 고려하여 탐색범위를 축소한다. 이를 Centralized Global Search(CGS)라 하며, 이 과정은 새로운 매개변수 Centralized Global Search Rate(CGSR)에 의해 HS의 전역탐색과는 별도로 진행된다. 축소된 탐색범위는 효과적인 전역탐색을 가능하게 하며, 이를 통해 알고리즘의 성능이 향상된다. EBHS-CGS를 대표적인 최적화 문제(수학 및 공학 분야)에 적용하고, 그 결과를 HS와 Improved Harmony Search(IHS)와 비교하여 제시하였다.

• 한국통신학회논문지
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• 제25권9A호
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• pp.1405-1412
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• 2000

In this paper, we propose an efficient dynamic wavelength assignment algorithm in distributed WDM (Wavelength-Division Multiplexing) networks without wavelength conversion. The algorithm tries to assign a locally-most-used wavelength distributedly on a fixed routing path. We first formulate our algorithm by using the concept of a sample space which consists of optical fibers connected to nodes on a routing path of a lightpath to be assigned a wavelength. In particular, we analyze the blocking performance mathematically as compared with that of the most-used (MU) wavelength assignment algorithm previously proposed for WDM networks under centralized control. We also obtain numerical results by simulation on the blocking performance of other centralized/distributed wavelength assignment algorithms as well as our algorithm using the M/M/c/c dynamic traffic model. Consequently, we show that analytical results match simulation results and that our algorithm is efficient in distributed WDM networks in terms of blocking performance, control traffic overhead and computation complexity.

• 한국항공운항학회지
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• 제24권2호
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• pp.1-10
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• 2016

A GPS/SDINS/ST(Star Tracker) integrated sensor algorithm is more robust than the GPS/SDINS and the ST/SDINS systems on exploration of other planets. Most of the advanced studies shown that GPS/SDINS/ST integrated sensor with centralized Kalman filter was more accurate than those 2 integrated systems. The system, however, consist of a single filter, it is vulnerable to defects on failed data. To improve the problem, we work out a study using federated Kalman filter(No-Reset mode) and centralized Kalman filter with adaptive measurement fusion which known as robustness on fault. The simulation results show that the debasing influences are reduced and the computation is enable at least 100Hz. Further researches that the initial calibration in accordance with observability and applying the exploration trajectory are needed.

• International Journal of Control, Automation, and Systems
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• 제4권2호
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• pp.165-171
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• 2006

This paper proposes a data fusion algorithm of nonlinear multi sensor dynamic systems of synchronous sampling based on filtering step by step. Firstly, the object state variable at the next time index can be predicted by the previous global information with the systems, then the predicted estimation can be updated in turn by use of the extended Kalman filter when all of the observations aiming at the target state variable arrive. Finally a fusion estimation of the object state variable is obtained based on the system global information. Synchronously, we formulate the new algorithm and compare its performances with those of the traditional nonlinear centralized and distributed data fusion algorithms by the indexes that include the computational complexity, data communicational burden, time delay and estimation accuracy, etc.. These compared results indicate that the performance from the new algorithm is superior to the performances from the two traditional nonlinear data fusion algorithms.