• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.12
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• pp.2480-2483
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• 2009

This paper presents an LMI-based method to design a integral sliding mode controller for a class of uncertain time-delay systems. Using LMIs we derive an existence condition of a sliding surface guaranteeing the asymptotic stability of the sliding mode dynamics. And we give a switching feedback control law. Our method is a generalization of the previous integral sliding mode control design methods. Since our method is based on LMIs, it gives design flexibility for combining various useful design criteria that can be captured in the LMI-based formulation. We also give LMI existence conditions of sliding surfaces guaranteeing a-stability or LQ performance constraint. Finally, we give a numerical design example to show the effectiveness of the proposed method.

• Proceedings of the KIPE Conference
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• 2003.11a
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• pp.36-40
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• 2003

On analyzing the power circuit of a DVR system, control limitations and control targets are presented for the voltage compensation in DVRs. The control delay in digital controllers increases the dimension of the system transfer function one degree higher which makes the control system more complicate and more unstable. Based on the power stage analysis, a novel controller for the compensation voltages in DVRs is proposed by a feedforward control scheme. Proposed controller works well with the time delay in the digital control system. This paper also proposes a guide line to design the control gain, appropriate output filter parameters and inverter switching frequency for DVRs in digital controllers. Proposed theory is verified by an experimental DVR system with a typical digital controller.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1124-1133
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• 2000

Advanced Intelligent Network Intelligent Peripheral (AIN IP) is one of the AIN elements which consist of Service Control Point (SCP), Service Switching Point (SSP), and IP for AIN services, such as play announcement, digit collect, voice recognition/synthesis, voice prompt and receipt. This paper, featuring ISUP/INAP protocols, describes the procedures for call setup/release bearer channels between SSP/SCP and IP, todeliver specialized resources through the bearer channels, and it describes the structure and procedure for AIN services such as Automatic Collect Call (ACC), Universal Personal Telecommunication (UPT), and teleVOTing(VOT). In this environments, the delay characteristics of If system is investigated as the performance analysis, Policy establishment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.10
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• pp.35-42
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• 2003

In this paper, we classified the wavelength reservation mechanisms of optical burst switching (OBS), and investigated the path length priority effect of the offset time/delayed reservation (OT/DR)-based scheme like the just-enough-time (JET) protocol. And, we showed that the fiber delay line (FDL)-based scheme can avoid the path length priority effect in multiple hop network environments. Also, we proposed a novel FDL/DR with hop-by-hop priority increasing (HPI) scheme which can improve the end-to-end throughput by increasing the priority of bursts hop-by-hop using the input FDLs at each node. The simulation results showed that the proposed FDL/DR with HPI scheme could avoid the path length priority effect and enhance the end-to-end throughput in multiple hop network environments.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.729-738
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• 1995

We consider a priority-based packet-switching system with three phases of the packet transmission time. Each packet belongs to one of several priority classes, and the packets of each class arrive at a switch in a Poison process. The switch transmits queued packets on a priority basis with three phases of preemption mechanism. Namely, the transmission time of each packet consists of a preemptive-repeat part for the header, a preemptive-resume part for the information field, and a nonpreemptive part for the trailer. By an exact analysis of the associated queueing model, we obtain the Laplace-Stieltjes transform of the distribution function for the delay, i.e., the time from arrival to transmission completion, of a packet for each class. We derive a set of equations that calculates the mean response time for each class recursively. Based on this result, we plot the numerical values of the mean response times for several parameter settings. The probability generating function and the mean for the number of packets of each class present in the system at an arbitrary time are also given.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.1
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• pp.78-101
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• 2017

High-quality industrial control is critical to ensuring production quality, reducing production costs, improving management levels and stabilizing equipment and long-term operations. WiFi-based Long Distance (WiLD) networks have been used as remote industrial control networks. Real-time performance is essential to industrial control. However, the original mechanism of WiLD networks does not minimize end-to-end delay and restricts improvement of real-time performance. In this paper, we propose two algorithms to obtain the transmitting/receiving phase cycle length for each node such that real time constraints can be satisfied and phase switching overhead can be minimized. The first algorithm is based on the branch and bound method, which identifies an optimal solution. The second is a fast heuristic algorithm. The experimental results show that the execution time of the algorithm based on branch and bound is less than that of the heuristic algorithm when the network is complex and that the performance of the heuristic algorithm is close to the optimal solution.

• Journal of Internet Computing and Services
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• v.7 no.1
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• pp.143-150
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• 2006

The quickest path problem deals with the transmission of a message of size ${\sigma}$ from a source to a destination with the minimum end to end delay over a network with bandwidth and delay constraints on the links. We consider two basic modes and four variations for the message delivery at the nodes reflecting the mechanisms such as circuit switching. Internet protocol, and their combinations, For each of first five modes, we present O($m^2+mnlogn$) algorithm to compute the quickest path for a given message size ${\sigma}$, For the last mode, the quickest path can be computed in O(m+nlogn) time.

• Current Optics and Photonics
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• v.7 no.3
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• pp.297-303
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• 2023

In this paper, we demonstrated a high-energy (285 mJ) mid-infrared flashlamp-pumped electro-optically 𝚀-switched Er:YAG master oscillator power amplifier (MOPA) system and comprehensively investigated its temporal, spectral, and spatial characteristics. To increase the output energy, we optimized the delay between the timings at which the flashlamps of the master oscillator and power amplifier were triggered. In addition, the output energy was improved while minimizing thermal effects by cooling the MOPA system to a temperature slightly above the dew point. Consequently, the MOPA structure boosted the output energy without damaging the lithium niobate Pockels cell, which is a crucial element in 𝚀-switching. This design realized pulses with energies up to 0.285 J and pulse durations of approximately 140 ns at a wavelength of 2,936.7 nm. This high-energy mid-IR Er:YAG MOPA system can be used for various scientific, engineering, and military underwater applications.

• ETRI Journal
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• v.24 no.4
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• pp.311-322
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• 2002

Presently, optical burst switching (OBS) technology is under study as a promising solution for the backbone of the optical Internet in the near future because OBS eliminates the optical buffer problem at the switching node with the help of no optical/electro/optical conversion and guarantees class of service without any buffering. To implement the OBS network, there are a lot of challenging issues to be solved. The edge router, burst offset time management, and burst assembly mechanism are critical issues. In addition, the core router needs data burst and control header packet scheduling, a protection and restoration mechanism, and a contention resolution scheme. In this paper, we focus on the burst assembly mechanism. We present a novel data burst generation algorithm that uses hysteresis characteristics in the queueing model for the ingress edge node in optical burst switching networks. Simulation with Poisson and self-similar traffic models shows that this algorithm adaptively changes the data burst size according to the offered load and offers high average data burst utilization with a lower timer operation. It also reduces the possibility of a continuous blocking problem in the bandwidth reservation request, limits the maximum queueing delay, and minimizes the required burst size by lifting up data burst utilization for bursty input IP traffic.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.11
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• pp.1139-1145
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• 2008

A robust position sensing system is proposed in this paper for a ubiquitous mobile robot which moves indoors as well as outdoors. The Differential GPS (DGPS) which has a position estimation error of less than 5 m is a general solution when the mobile robot is moving outdoor, while an active beacon system (ABS) with embedded ultrasonic sensors is reliable as an indoor positioning system. The switching from the outdoor to indoor or vice versa causes unstable measurements on account of the reference coordinates and algorithm changes. To minimize the switching time in the position estimation and to stabilize the measurement, a robust position sensing system is proposed. In the system, to minimize the switching delay, the door positions are stored and updated in a database. Using the database, the approaching status of the mobile robot from indoor to outdoor or vice versa has been checked and the switching conditions are prepared before the mobile robot actually moves out or moves into the door. The reliability and accuracy of the robust positioning system based on DGPS and ABS are verified and demonstrated through the real experiments using a mobile robot prepared for this research.