• Journal of Internet of Things and Convergence
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• v.9 no.1
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• pp.125-129
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• 2023

Age of Information (AoI) has been introduced in wireless networked control systems (WNCSs) to guarantee timely status updates. In addition, as the edge computing (EC) architecture has been deployed in NCS, EC close to sensors can be exploited to collect status updates from sensors and provide control decisions to actuators. However, when lots of sensors simultaneously deliver status updates, EC can be overloaded, which cannot satisfy the AoI requirement. To mitigate this problem, this paper uses actuators with computing capability that can directly receive the status updates from sensors and determine the control decision without the help of EC. To analyze the AoI of the actuation update via EC or directly using actuators, this paper developed an analytic model based on timing diagrams. Extensive simulation results are included to verify the analytic model and to show the AoI with various settings.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.39-40
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• 2008

본 논문은 네트워크 기반 제어시스템(NCS: Networked Control Systems)모델매칭 제어기법을 적용한 효율적인 제어알고리즘을 제안한다. 비선형의 특징을 가지는 제어기 및 관측기의 시간지연을 Pade 근사법으로 선형화하여 선형시스템 이론을 적용한 모델매칭 제어기를 설계하였다. 또한, 제어기의 차수를 줄이기 위하여 저차시스템으로 근사화하여 그 타당성을 검증하였다. 제안한 제어알고리즘의 타당성 및 신뢰성을 검증하기 위하여 컴퓨터 시뮬레이션을 실시하였으며 기존의 PID 제어기법과 비교분석하였다.

• ETRI Journal
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• v.39 no.1
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• pp.13-20
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• 2017

A method is proposed for scheduling sensor accesses to the shared network in a networked control system. The proposed method determines the access order in which the sensors are granted medium access through minimization of the state estimation error covariance. Solving the problem by evaluating the error covariance for each possible ordered set of sensors is not practical for large systems. Therefore, a convex optimization problem is proposed, which yields approximate yet acceptable results. A state estimator is designed for the augmented system resulting from the incorporation of the optimally chosen communication sequence in the plant dynamics. A car suspension system simulation is conducted to test the proposed method. The results show promising improvement in the state estimation performance by reducing the estimation error norm compared to round-robin scheduling.

• Nuclear Engineering and Technology
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• v.41 no.1
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• pp.71-78
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• 2009

One of main concepts involved in regional small nuclear reactors is unmanned remote control. Internet-based virtual private networks provide environments for the remote monitoring and control of geographically-dispersed systems, and with the advances in communication technologies, the potential of networks for real time control and automation becomes enormous. However, networked control has some problems. The most critical is delay in signal transmission, which degrades system stability and performance. Therefore, a networked control system should be designed to account for delay. This paper proposes some design approaches for a delay-tolerant system that can guarantee predetermined stability margins and performance. To accomplish this, the reactor plant is modeled with consideration of uncertainties. With this model, three kinds of controllers are developed using different methods. The designed systems are compared with respect to stability and performance, and a second-order controller designed using the table lookup method was found to give the most satisfactory results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.302-308
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• 2006

We introduce the concept of a remote distributed embedded system to integrated fieldbus based control systems in internet/Intranet. As a result fieldbus systems are opened up for remote monitoring, remote maintenance, and remote control applications using state of the art Web-technology. This paper addresses the design of a remote distributed embedded system using Internet and CAN for multi-Induction motor of Building and Industrial field. The fieldbus used the CAN based networked intelligent multi-motor control system using DSP2812 microprocessor. To build such a system, the TCP/IP-CAN Gateway which convert a CAN protocol to TCP/IP protocol and vice verse, was designed. A experimental simulation system consists of a TCP/IP-CAN Gateway in remote place and a command PC ti be connected ti Ethernet.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.54.6-54
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• 2002

1. Introduction 2. The Netwoked Control System Description 2.1 A close-loop system with the network induced delay 2.2 Discretization and State Augmentation of NCS 3. Delay-dependent H_infinity Controller Design for NCS 4. Numerical Example 5. Conclusion

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.9
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• pp.3635-3654
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• 2015

With the rapid development of smart devices and mobile Internet, the video application plays an increasingly important role on mobile devices. Understanding user behavior patterns is critical for optimized operation of mobile live streaming systems. On the other hand, volume based billing models on cloud services make it easier for video service providers to scale their services as well as to reduce the waste from oversized service capacities. In this paper, the watching behaviors of a commercial mobile live streaming system are studied in a content-centric manner. Our analysis captures the intrinsic correlation existing between popularity and watching intensity of programs due to the synchronized watching behaviors with program schedule. The watching pattern is further used to estimate traffic volume generated by the program, which is useful on data volume capacity reservation and billing strategy selection in cloud services. The traffic range of programs is estimated based on a naive popularity prediction. In cross validation, the traffic ranges of around 94% of programs are successfully estimated. In high popularity programs (>20000 viewers), the overestimated traffic is less than 15% of real happened traffic when using upper bound to estimate program traffic.

• The Journal of Society for e-Business Studies
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• v.13 no.4
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• pp.93-110
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• 2008

Reference modeling for Collaborative Networked Organizations(CNOs) has just started, and Enterprise Architecture Modeling Languages(EAMLs) for CNOs are very few. Lack of reference models makes it difficult for people to communicate with each other and lack of EAMLs also makes it difficult to implement information systems for CNOs. We propose an EAML for CNO called CAML. It supports (1) multi-level modeling based on Model- Driven Architecture of OMG's for expressive power and efficiency of implementations, and (2) multi-focus modeling based on Zachman Framework for completeness of modeling The effectiveness of the CAML is investigated through modeling of a supply chain and execution of change impact analysis.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.2 no.1
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• pp.59-66
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• 2001

Networked Virtual Reality systems provide a consistent virtual world to the users, possibly ditributed across long distance, and have been widely applied in the military war game, network game. edutainment, architectural areas, and shopping mall etc. Large processing requirements. however. made these systems be mainly researched on the platforms of high-performence system graphics workstations. This study paper Presents several problems when networked virtual reality systems are implemented on commodity Internet : two problems related with 3D graphical Processing, and the other related with network bandwidth and transmission delay. We also suggest solutions to these problems and analyze their performance effect based on an architectural simulation application.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.2
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• pp.151-156
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• 2008

This paper presents the stability analysis and design for a sampled-data fuzzy control system with neutral type of time delay, which is formed by a nonlinear plant and a sampled-data fuzzy controller connected in a closed loop. The sampling activity and neutral type of time delay will complicate the system dynamics and make the stability analysis much more difficult than that for a pure continuous-time fuzzy control system. Based on the fuzzy-model-based control approach, LMI(linear matrix inequality)-based stability conditions are derived to guarantee the nonlinear networked system stability. An application example will be given to show the merits and design a procedure of the proposed approach.