• Proceedings of the Korean Information Science Society Conference
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• 2007.06b
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• pp.372-376
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• 2007

분산처리 시스템은 네트워크로 연결된 프로세서들로 구성되며, 시스템 내의 각 프로세서는 고유한 클럭을 갖는다. 글로벌 시간 기준으로 볼 때 수행중인 프로세스가 유지하는 시간은 분산시스템 각각 차이가 있을 수 있으므로 일관성 있는 시간관리가 필요하다. 본 논문에서는 TMO-eCos를 기반으로 하는 분산 처리 시스템에서 각 분산 시스템간 발생할 수 있는 클럭의 불일치 문제를 해결하기 위한 클럭 동기화 기법에 관해 논한다. 점진적인 클럭 동기화 알고리즘을 구하기 위해 마스터 노드의 클럭을 글로벌 클럭으로 가정하고 슬레이브 노드들은 마스터 노드의 클럭으로 동기화하는 방법에 대하여 정의하였다. 정의한 알고리즘을 시현하기 위한 분산 노드 간 로봇 제어 프로그램을 소개 한다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 1995.05a
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• pp.163-172
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• 1995

100 MW급 유류연소 드럼형 열병합발전소의 주증기온도 제어를 위한 비선형 process model based control (PMBC)을 개발하고 그 성능을 PID 알고리즘과 비교하였다. 비선형 PMBC에서는 프로세스의 메캐니즘을 비교적 충실히 반영하는 모델이 필요한데, 사용된 모델은 first principle approach를 사용하여 개발된 것으로 제어기 성능 평가와 설계에 적합한 정교한 것이다. 비선형 PMBC는 비선형 피드백, feedforward, decoupling을 제공하고 분산제어에 적합하면서 모델링 오차에 민감하지 않은 장점이 있다. PMBC와 PID 제어의 성능을 부하증가와 연료의 열량변화등의 외란에 비교한 결과, PMBC가 PID에 비하여 속응성, 절대오차 적분치, 제어노력등에서 월등하게 우수한 것을 확인하였다.

• Journal of the Korean Society of Safety
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• v.18 no.3
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• pp.154-160
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• 2003

Uncertain time delay happens when the process reads the sensor data and sends the control input to the plant located at a remote site in distributed control system. As in the case of data network using TCP/IP, VDN that integrates both device network and data network has uncertain time delay. Uncertain time delay can cause degradation in performance and stability of distributed control system based on VDN. This paper first investigates the transmission characteristic of VDN and suggests a control scheme based on the Smith's predictor to minimize the effect of uncertain varying time delay. The validity of the proposed control scheme is demonstrated with real-time velocity control of DC servo motor located in remote site.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9A
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• pp.1395-1404
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• 2000

In this paper, we propose a heuristic wavelength routing algorithm for IP datagrams in WDM (Wavelength-Division Multiplexing) networks which operates in a distributed manner, while most previous works have focused centralized algorithms. We first present an efficient construction method for a loose virtual topology with a connectivity property, which reserves a few wavelength to cope with dynamic traffic demands properly. This connectivity property assures that data from any source node could reach any destination node by hopping one or multiple lightpaths. We then develop a high-speed distributed wavelength routing algorithm adaptive to dynamic traffic demands by using such a loose virtual topology and derive the general bounds on average utilization in the distributed wavelength routing algorithms. Finally, we show that the performance of the proposed algorithms is better than that of the FSP(Fixed Shortest-Path) wavelength routing algorithms through simulation using the NSFNET[1] and a dynamic hot-spot traffic model, and that the algorithms is a good candidate in distributed WDM networks in terms of the blocking performance, the control traffic overhead, and the computation complexity.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1701-1705
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• 2008

이 논문은 건물내 또는 건물군 단위로 설치될 신.재생에너지 원격제어를 위한 분산 임베디드시스템에 관한 연구로 제어시스템은 CAN통신을 기반으로 하는 네트워크를 구성하였으며 원격제어를 위하여 Ethernet TCP/IP-CAN 게이트웨이를 개발하였다. 이의 성능을 평가하기 위하여 본 실험실에 설치된 유도전동기 2대의 구동시스템을 활용하여 원격제어실험을 수행하였으며 실험 결과 개발된 알고리즘 및 TCP/IP-CAN 게이트웨이가 매우 우수한 성능을 가지고 있음을 확인하였다.

• Journal of Advanced Navigation Technology
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• v.26 no.4
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• pp.226-234
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• 2022

With advances in autonomous vehicles and networked control, there is a growing interest in the consensus control of a multi-agents system to control multi-agents with distributed control beyond the control of a single agent. Since consensus control is a distributed control, it is bound to have delay in a practical system. In addition, it is often difficult to have a very accurate mathematical model for a system. Even though a reinforcement learning (RL) method was developed to deal with these issues, it often experiences slow convergence in the presence of large uncertainties. Thus, we propose a slide RL which combines the sliding mode control with RL to be robust to the uncertainties. The structure of a sliding mode control is introduced to the action in RL while an auxiliary sliding variable is included in the state information. Numerical simulation results show that the slide RL provides comparable performance to the model-based consensus control in the presence of unknown time-varying delay and disturbance while outperforming existing state-of-the-art RL-based consensus algorithms.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.8
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• pp.523-530
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• 2022

Since the Multi-UAV system for various missions is more complex than a single UAV, an efficient formation control method is required. In wide-area search mission, there is a need for a distributed control for flexible formation that has a low burden of communication and computation and enables autonomous formation between UAVs. This paper proposes a flexible formation operation method that considers the swarm formation, the bank alignment formation, and the formation movement to expand the scan area and improve search performance. The algorithm has a vibration characteristic of the second-order system for a relative distance and can design an algorithm through parameter tuning. In addition, we converted control commands to suit conventional UAV systems and demonstrated the performance of algorithms for a formation and movement of a formation through simulation.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.9
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• pp.469-478
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• 2001

It is difficult to test a distributed system because of the task of controlling concurrent events,. Existing works do not propose the test sequence generation algorithm in a formal way and the amount of message is large due to synchronization. In this paper, we propose a formal test sequence generation algorithm using logical clock to control concurrent events. It can solve the control-observation problem and makes the test results reproducible. It also provides a generic solution such that the algorithm can be used for any possible communication paradigm. In distributed test, the number of channels among the testers increases non-linearly with the number of distributed objects. We propose a new remote test architecture for solving this problem. SDL Tool is used to verify the correctness of the proposed algorithm and it is applied to the message exchange for the establishment of Q.2971 point-to-multipoint call/connection as a case study.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.1-9
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• 2016

Train control systems have changed from wayside electricity-centric to onboard communications-centric. The latest train control system, the CBTC system, has high efficiency for interval control based on two-way radio communications between the onboard and wayside systems. However, since the wayside system is the center of control, the number of input trains to allow a wayside system is limited, and due to the cyclic-path control flows between onboard and wayside systems, headway improvement is limited. In this paper, we propose a train interval-control and train-centric distributed interlocking algorithm for an autonomous train-driving control system. Because an autonomous train-driving control system performs interval and branch control onboard, both tracks and switches are shared resources as well as semaphore elements. The proposed autonomous train-driving control performs train interval control via direct communication between trains or between trains and track-side apparatus, instead of relying on control commands from ground control systems. The proposed interlocking algorithm newly defines the semaphore scheme using a unique key for the shared resource, and a switch that is not accessed at the same time by the interlocking system within each train. The simulated results show the proposed autonomous train-driving control system improves interval control performance, and safe train control is possible with a simplified interlocking algorithm by comparing the proposed train-centric distributed interlocking algorithm and various types of interlock logic performed in existing interlocking systems.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1206-1207
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• 2011

하이브리드 발전시스템에서 전압과 주파수제어는 서로 다른 분산전원의 동기화 및 전력제어에 있어서 매우 중요하다. 본 논문에서는 디젤 발전 시스템에서 연료 분사량을 제어하여 주파수를 담당하는 Governor 제어기에 대한 제어 알고리즘을 개발하여 적용함으로써, 연료분사량을 최적화하여 일정한 속도제어를 하고자 한다. 이는 기본 제어기 알고리즘에 전력에 대한 전류 지령치를 첨가함으로서 제어기의 속응성 및 안정도를 개선할 수 있다. 또한 기존 디젤발전기의 부하에 따른 전압 및 주파수 특성을 분석하고, 시뮬레이션 함으로서 본 알고리즘을 검증하였다.