• Journal of Sensor Science and Technology
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• v.16 no.1
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• pp.52-61
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• 2007

Networked embedded systems using the smart device and fieldbus technologies are now found in many industrial fields including process automation and automobiles. However the discrepancy between a node's view of current time and the rest of the system can cause many difficulties in the design and implementation of a networked system. To provide a networked system with a global reference time, the problem of clock synchronization has been intensively studied over the decades. However, many of the existing solutions, which are mainly developed for large scale distributed computer systems, cannot be directly applied to embedded systems. This paper presents a fault-tolerant clock synchronization technique that can be used for a low-cost embedded system using a CAN bus. The effectiveness of the proposed method is demonstrated with a set of microcontrollers and DC motor-based actuators.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.221-226
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• 2009

Not many years ago, people found the contemporary technology expensive and difficult to use in collaborative type of meetings. Today, with the technology advanced to high standards and accessible at cheaper price, its adaption is becoming more and more ubiquitous with wide range of applications. Today's meeting rooms are not just plain old telephone systems with microphones and speakers. Today's meeting rooms are smart and intelligent. They can identify the participants; they can provide natural view of remote participants; they can proactively manage resources for collaboration and so on. More effective collaboration is possible with deployment of devices like high-definition cameras, advanced displays, sensors, gigabit networks, trackers, pointers, and high-end audio devices. Devices alone are not enough in the meeting rooms. We need software infrastructure to manage the devices and meeting contexts. One such software infrastructure is SMeet, a Smart Meeting space, which we have developed to provide an effective multi-party remote collaboration environment. Networked display systems are used in such advanced collaboration environment for better visualization. In this paper we discuss a novel approach to control and manage networked display systems in SMeet environment.

• IEMEK Journal of Embedded Systems and Applications
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• v.4 no.2
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• pp.97-102
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• 2009

In this paper, the problem of stability analysis for networked control systems with norm-bounded parameter uncertainties is investigated. By construction Lyapunov's functional, a new delay-dependent stability criterion for uncertain networked control system is established in terms of LMIs (linear matrix inequalities) which can be easily by various convex optimization algorithms. One numerical example is included to show the effectiveness of proposed criterion.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.11
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• pp.1131-1135
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• 2014

This paper proposes the enhanced faulty node detection scheme with hybrid algorithm using Markov-chain model on BCH (Bose-Chaudhuri-Hocquenghem) code in naval distributed control networked systems. The probabilistic model-driven approach, on Markov-chain model, in this paper uses the faulty weighting interval factors, which are based on the BCH code. In this scheme, the master node examines each slave-nodes continuously using three defined states : Good, Warning, Bad-state. These states change using the probabilistic calculation method. This method can improve the performance of detecting the faulty state node more efficiently. Simulation results show that the proposed method can improve the accuracy in faulty node detection scheme for real-time naval distributed control networked systems.

• International Journal of Control, Automation, and Systems
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• v.5 no.4
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• pp.372-378
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• 2007

This paper discusses Robust $H{\infty}$ control problems for networked control systems (NCSs) with time delays and subject to norm-bounded parameter uncertainties. Based on a new discrete-time model, two approaches of robust controller design are proposed. A numerical example and experimental verification with an NCS test bed are given to illustrate the feasibility and effectiveness of proposed design methodologies.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2328-2330
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• 2003

This paper presents a new design methodology of networked control system using CAN(Controller Area Network). Feedback control systems having control loops closed through a network are called networked control systems. We design CAN nodes which can transmit control and monitoring data through network bus and apply these to networked control system design. We analyze the variation of stability property according to network-induced delay and determine a proper sampling period of networked control system that preserves stability performance. The results of the experimental example validate effectiveness of our networked control system.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.10
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• pp.678-689
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• 2004

The major concern of networked control system is network uncertainties such as time delay and data loss. Because these uncertainties may degrade the performance of networked control system and destabilize the entire system. Therefore, the performance and the stability variation of networked control system due to network uncertainties must be considered first in designing networked control system. In particular, the stability analysis of networked control system is most important issue since time delay and data loss can make the overall systems unstable. In this paper, we present a new stability analysis method of networked control system with time delay and data loss, which is impossible in previous works. The proposed method can determine maximum time delay and allowable transmission rate that preserve stability performance of networked control system. The results of the simulation validate effectiveness of our stability analysis method.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.1
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• pp.80-88
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• 2002

As many sensors and actuators are used in automated systems, various industrial networks are adopted for digital control system. In order to take advantages of the networking, however, the network implementation should be carefully designed to satisfy real-time requirements considering network delays. This paper presents the implementation scheme of a networked control system via Profibus-DP network. More specifically, the effect of the network delay on the control performance was evaluated on a Profibus-DP testbed, and a GA-based PID tuning algorithm is proposed to design controllers suitable for networked control systems.

• KIEE International Transaction on Systems and Control
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• v.2D no.2
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• pp.72-77
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• 2002

Delay and noise in networked control systems are inevitable and can degrade system performance or stability This paper propose a compensation method for networked control systems with network-induced delay and noise using LMI(linear matrix inequality)-based H_\infty optimization. The H_\infty optimization methods have adapted to account for both the time delay and noise effects. Some simulations applied to inverted pendulum with networked control show that the proposed method works well.

• Journal of IKEEE
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• v.23 no.3
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• pp.899-903
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• 2019

In networked control systems, time-varying delay of the transmitting signal is inevitable. If the transmission delay is longer than the fixed sampling time, the system will be unstable. To solve this problem, this paper proposes the method to predict the delay using logic-based fuzzy neural networks, and the predicted time delay will be used as a sampling time in the networked control systems. To verify the effectiveness of the proposed method, the delay data collected from the real system are used to train and test the logic-based fuzzy neural networks.