• Journal of Advanced Marine Engineering and Technology
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• 제22권2호
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• pp.174-180
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• 1998

Robust stability of discrete-time regulators which utilize state predictors to compensate computation delays is considered. Novel expressions for the return difference matrices and the complementary sensitivity matrices at the input and the output of the regulator are found to obtain simple bounds for unstructured perturbations. Robust stability for pertubations of the system matrix and /or the gain matrix is also considered. under certain restriction on the nominal system simple bounds for the pertubations are obtained directly from the characteristic equation. It is shown that as far as the effect of the computation delays concerns these bounds have explicit relation to those for the unstructured pertubations.

• 대한전기학회논문지
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• 제40권9호
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• pp.937-944
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• 1991

In digital controller design, the delays in the controller should be taken into consideration when the computation time of the processor is not negligibale compared with sampling time. Recently, Mita has proposed a digital optimal servosystem taking account of the delays in the controller. In this paper, robust stability and diturbance rejection properties of this optimal servosystej are analyzed in the frequency-domain. The well-known asymptotic properties of the optimal regulators with respect to the weighting matrices of the cost functions are successfully utilized to show that the influence of the delays in the controller are drastic for certain choice of the cost function Illustrative numerical examples are presented.

• 대한전기학회논문지
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• 제36권6호
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• pp.437-443
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• 1987

Due to the recent development of microprocessor, the digital control is now in use for the practical structure of the control systems, but it leaves the problem of controlling delays caused by computation time when it is applied to the realization problems, such as application method of the control law and controlling effect of continuous control, etc. This paper deals with robust stability of the digital regulator which compensates for the controlling delays by applying prediction values of state.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권5호
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• pp.190-196
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• 2002

In this paper, the response characteristics of CAN-based feedback control system are analyzed when message time delays through the network are considered. The message time delays are composed of computation time delay and communication time delay. The application layer of CAN communication is modeled mathematically to analyze two time delays, and the communication time delay is redefined under several assumption conditions. The CAN-based feedback control system is proposed as a target system that is the machining system with the three axes. The response characteristics of time delays in the proposed system are analyzed through computer simulations, and can be improved by the compensation using the PID tuning method to satisfy the design specifications of the system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.348-353
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• 2003

This paper considers the optimal control problem in real-time control systems with random time-delays. It proposes an algorithm which uses the linear quadratic (LQ) control method and a dedicated technique to compensate for the time-delay effects. Since it is assumed that the time-delays are unknown but the probability distribution of the delays are known a priori, the algorithm considers the mean value of the time-delays as a nominal value for random delay compensation. An example is given to show the performance of the proposed algorithm, where an inverted pendulum system is controlled over a controller-area network (CAN). Simulation results show that the proposed algorithm provides good performance results. It is shown that our algorithm is comparable to existing algorithms in both computation cost and performance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.748-752
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• 1991

Tree network consisting of communicating processors is considered. The objective is to minimize the computation time by distributing the processing load to other nodes. The effect of the order of load distribution on the processing time is addressed. An algorithm which optimally determines the order of load distribution is developed. It is shown that the order depends only on the channel capacity between nodes but not on the computing capability of each node.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권1호
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• pp.149-165
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• 2013

Current group key agreement protocols, which are often tree-based, have unnecessary delays that are caused when members with low-performance computer systems join a group key computation process. These delays are caused by the computations necessary to balance a key tree after membership changes. An alternate approach to group key generation that reduces delays is the dynamic prioritizing mechanism of queue-based group key generation. We propose an efficient group key agreement protocol and present the results of performance evaluation tests of this protocol. The queue-based approach that we propose is scalable and requires less computational overhead than conventional tree-based protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권7호
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• pp.1737-1753
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• 2013

Current group key agreement protocols, which are often tree-based, have unnecessary delays that are caused when members with low-performance computer systems join a group key computation process. These delays are caused by the computations necessary to balance a key tree after membership changes. An alternate approach to group key generation that reduces delays is the dynamic prioritizing mechanism of queue-based group key generation. We propose an efficient group key agreement protocol and present the results of performance evaluation tests of this protocol. The queue-based approach that we propose is scalable and requires less computational overhead than conventional tree-based protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권2호
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• pp.178-194
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• 2009

Current group key agreement protocols(often tree-based) involve unnecessary delays because members with low-performance computer systems can join group key computation. These delays are caused by the computations needed to balance a key tree after membership changes. An alternate approach to group key generation that reduces delays is the dynamic prioritizing mechanism of filtering low performance members in group key generation. This paper presents an efficient tree-based group key agreement protocol and the results of its performance evaluation. The proposed approach to filtering of low performance members in group key generation is scalable and it requires less computational overhead than conventional tree-based protocols.

• 대한교통학회지
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• 제31권4호
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• pp.3-17
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• 2013

본 연구는 대규모 교통망에서 통행배정시 신호교차로에 의한 지체를 반영한 통행배정을 수행하여 보다 현실 모사가 가능한 통행배정기법을 개발 하는 것이다. 실제로 도시부나 단속류에서 발생하는 통행시간 및 비용의 증가 원인은 많은 부분이 교차로 지체에 의한 정지 혹은 혼잡에 의해 발생함에도 불구하고 기존의 통행배정 모형은 이를 반영하지 못하고 있었다. 본 연구에서 개발한 신호교차로 지체 반영 통행배정 모형은 기존의 통행배정모형과 한국도로 용량편람의 신호교차로 지체 산정 방법을 결합하여 구축하였다. 다양한 모의실험을 통해 이 모형이 실제 가로망에 적용이 가능한 모형임을 보였다. 따라서 본 모형은 대규모 지역에서의 교통정책 및 교통시설의 변화 등에 교차로 지체를 적용하여 분석할 수 있을 것으로 판단된다.