• 한국통신학회논문지
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• 제23권9A호
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• pp.2184-2196
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• 1998

Admission control is one of the most important congestion control mechanism to be executed at the call set up phase by regulating traffic into a network in a preventive way. An efficient QOS evaluation or bandwidth estimation method is required for call admission to be decided in real time. In this paper, we spropose a computtionally simple approximation method of estimating cell loss probability and mean cell delay for admission control of both delay sensitive and loss sensitive calls. Mixed input queueing system, where a new call combines with the existing traffic, is used as a queueing model for QOS estimation. Also traffic parameters are suggested to characterize both a new call and existing traffic. Aggregate traffic is approximated by a renewal process with these traffic parameters and then mean delay and cell loss probability are detemined using appropriate approximation formulas. The accuracy of this approximation approach is examined by comparing their results with exact analysis or simulation results of vrious mixed unput queueing systems. Based on this QOS estimation method, call admission control scheme which is traffic independent and computable in yeal time are proposed.

• 한국통신학회논문지
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• 제22권3호
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• pp.593-603
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• 1997

Connection admission decision in ATM networks requires decision made in real time using fast algorithm. It is difficult to construct a model of the multiplexed traffic and thus, approximation of the traffic load is necessary. In this paper, we propose a measurement-based dynamic CAC(Connection admission Control) in ATM(Asynchronous Transfer Mode) networks, which observes current traffic by the moving window and set the window size to the value which is computed from the measured cell loss amount. It is based on the measurements of the traffic load over an admission period that is load enough to reflect the current traffic behavior instead of analytic modeling. And, the dynamic reallocation of bandwidth for each class leads to effective bandwidth utilization. The performance of proposed method is analyzed through computer simulation. The performance of proposed method is analyzed by using SIMAN simulation package and FORTRAN language. As can be seen in the simulation result, cell loss performance and bandwidth utilization have been increased.

• 전기학회논문지P
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• 제63권4호
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• pp.368-372
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• 2014

The most widely used scheme for detecting loss of excitation on generator is used to sense apparent impedance from generator terminals. This paper presents loss of excitation algorithm using DFT filter based negative offset mho elements for generator field protection. It's algorithm includes two negative mho characteristics looking in the generator. The generator control system was modeled by PSCAD/EMTDC software, and then the proposed algorithm was tested by the collecting relaying signals from selected the generator model. From simulation results, the loss of excitation algorithm can be used to field protection for generator.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.57.1-57
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• 2001

The objectives of congestion control in ATM (Asynchronous Transfer Mode) networks are maximum utilization of network resources, acceptable level of low cell loss and fairness among all VCs (Virtual Connections). In this paper, we present a congestion control algorithm which is based on state space model, The proposed controller uses optimal control algorithms (LQR, Mixed-LQR), where control parameters can be designed to ensure the stability of the control loop in a control theoretic sense, over the propagation delay. We show how the control mechanism can be used to design a controller to support ABR service based on feedback of explicit rates. Simulation results are presented to substantiate our claim.

• 제어로봇시스템학회논문지
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• 제17권7호
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• pp.704-713
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• 2011

For many years, many pilots lost their lives and aircrafts due to GLOC(Gravity-induced Loss Of Consciousness). Due to the emergence of high-gravity maneuvering aircraft such as the F-16, F-15 and T-50, the automatic GLOC detection and recovery systems are necessary to increase the aircraft safeties even when the pilot loses his consciousness due to high-G maneuvering. This paper addresses the design of GLOC detection, warning and recovery algorithm based on a model of supersonic jet trainer. The system is solely controlled by the pilot's control input (i.e., control stick force) and aircraft status such as attitude, airspeed, altitude and so forth. And, moreover, it does not depend upon any pilot physiological condition. The test evaluation results show that the developed system supports the recovery of an aircraft from the unusual aircraft attitude and improves the aircraft safeties even when the pilot loses his consciousness due to high-G maneuvering.

• 한국통신학회논문지
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• 제21권8호
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• pp.1989-2002
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• 1996

In this paper, we describe several warm standby fault-tolerant models and their operation methods applicable to telephone switching control systems which have dual module structure and need high availability. Unavailabilities of the system implemented by four different methods for each model are computed by using the Markov state model, and then are compared for system performance evaluation. As the results ofsimulations, the warm standby model with triple processors is best in the aspect of data loss, while in most cases the warm standby model with doble processors based on no standby check method provides the highest system avaiability. Periodic changeover increases the system unavailability, but the preriodic standby check on standby module decreases the system unavailability of warm standby model with a single processor and with double processors. On the other hands, the variationas of warm standby model with a single processor and with double processors. On the other hand, the variations of data recovery time and personnel recovery rate have little effect on the system unavailtability.

• Journal of Power Electronics
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• 제19권2호
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• pp.591-601
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• 2019

With the development of renewable energy, grid-connected inverter technology has become an important research area. When compared with traditional silicon IGBT power devices, the silicon carbide (SiC) MOSFET shows obvious advantages in terms of its high-power density, low power loss and high-efficiency power supply system. It is suggested that this technology is highly suitable for three-phase AC motors, renewable energy vehicles, aerospace and military power supplies, etc. This paper focuses on the SiC MOSFET behaviors that concern the parasitic component influence throughout the whole working process, which is based on a three-phase grid-connected inverter. A high-speed model of power switch devices is built and theoretically analyzed. Then the power loss is determined through experimental validation.

• International Journal of Control, Automation, and Systems
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• 제6권1호
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• pp.35-43
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• 2008

The control of underactuated mechanical system is very complex for the loss of its control inputs. The model of underactuated mechanical systems in a potential field is built with Lagrangian method and its structural properties are analyzed in detail. A genetic algorithm (GA)based stable control approach is proposed for the class of under actuated mechanical systems. The Lyapunov stability theory and system properties are utilized to guarantee the system stability to its equilibrium. The real-valued GA is used to adjust the controller parameters to improve the system performance. This approach is applied to the underactuated double-pendulum-type overhead crane and the simulation results illustrate the complex system dynamics and the validity of the proposed control algorithm.

• Journal of Power Electronics
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• 제13권4호
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• pp.679-691
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• 2013

High-power electromagnetic transmitter power supplies are an important part of deep geophysical exploration equipment. This is especially true in complex environments, where the ability to produce a highly accurate and stable output and safety through redundancy have become the key issues in the design of high-power electromagnetic transmitter power supplies. To solve these issues, a high-frequency switching power cascade based emission power supply is designed. By combining the circuit averaged model and the equivalent controlled source method, a modular mathematical model is established with the on-state loss and transformer induction loss being taken into account. A triple-loop control including an inner current loop, an outer voltage loop and a load current forward feedback, and a digitalized voltage/current sharing control method are proposed for the realization of the rapid, stable and highly accurate output of the system. By using a new algorithm referred to as GAPSO, which integrates a genetic algorithm and a particle swarm algorithm, the parameters of the controller are tuned. A multi-module cascade helps to achieve system redundancy. A simulation analysis of the open-loop system proves the accuracy of the established system and provides a better reflection of the characteristics of the power supply. A parameter tuning simulation proves the effectiveness of the GAPSO algorithm. A closed-loop simulation of the system and field geological exploration experiments demonstrate the effectiveness of the control method. This ensures both the system's excellent stability and the output's accuracy. It also ensures the accuracy of the established mathematical model as well as its ability to meet the requirements of practical field deep exploration.

• 한국정보처리학회논문지
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• 제3권2호
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• pp.305-314
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• 1996

B-ISDN망은 ATM방식으로 멀티미디어 정보를 전송하고자 할 때, 발생될 수 있는 셀의 종류로써 미디어 정보를 갖고 있는 미디어셀과 동기 정보를 갖고 있는 동기셀로 각각 분리하였다. 트래픽 입력원을 NO-OFF 발생원으로 하는 Leaky Buck에서 확률 분포 함수를 기반으로 한 미디어셀 손실식과 동기셀 손실식을 유도하였다. 멀티미디어 동기셀은 종기 정보의 무결성과 실시간 요건을 만족시키기 위해서는 지연 민감 요건과 손실 민감 요건을 모두 갖추어야 한다. 이러한 요건을 만족 시키기 위해 우선 순위 제어 기법이 필요할 트래픽 모델링 시뮬레이션을 통해 성능 평가한 걸과, 동기셀 손실 효과 를 최소화할 수 있는 공간 우선 순위 제어 기법과 동기셀 지연 효과를 최소화할 수 있는 시간 우선 순위 제어 기법을 동시에 적용하여야 하는 필요성을 제시하였다.