• 산업경영시스템학회지
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• 제6권9호
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• pp.35-38
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• 1983

In this paper major subject is to investigate the measurement errors affecting on the determination of observation numbers, which are required for work measurement, to set up the standard work time. The main consider is, however, with clarification of the differences between measurement errors in case of cycle operation being observed based on the continuous and the work elements observation.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회/대한산업공학회 2005년도 춘계공동학술대회 발표논문
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• pp.1137-1140
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• 2005

We present the discrete-time version of the heuristic interpretation of the mean waiting time known well about the continuous-time version. The heuristic approach is mainly based on an arriving customer's viewpoint. We obtain the mean waiting time of $Geo^X/G/1$ queueing systems, including vacation queues.

• Journal of Mechanical Science and Technology
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• 제14권8호
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• pp.807-815
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• 2000

In this paper, modified discrete time preview control algorithms for active and semi-active suspension systems are derived based on a simple mathematical 4 DOF half-car model. The discrete time preview control laws for ride comfort are employed in the simulation. The algorithms for MIMO system contain control strategies reacting against body forces that occur at cornering, accelerating, braking, or under payload, in addition to road disturbances. Matlab simulation results for the discrete time case are compared with those for the continuous time case and the appropriateness of the discrete time algorithms are verified by the of simulation results. Passive, active, and semi-active system responses to a sinusoidal input and an asphalt road input are analysed and evaluated. The simulation results show the extent of performance degradation due to numerical errors related to the length of the sampling time and time delay.

• 제어로봇시스템학회논문지
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• 제2권1호
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• pp.9-13
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• 1996

슬라이딩 모드 제어기의 실현시 발생하는 고주파 chattering 현상을 제거하기 위하여 본 논문에서는 스위칭 표면 행렬의 Range-space 동특성을 이용한 연속 시간 스위칭 다이나믹을 제안한다. 전체 폐루프 시스템은 정칙 변환에 의해 빠른 부시스템과 느린 부시스템으로 분해되어, 결국 전체 폐루프 시스템의 고유치는 각각 스위칭 표면 행렬의 Range-space와 Null-space의 동특성을 지배하는 부시스템들의 고유치들로 구성됨을 보인다. 그리고, 정합된 불확실성이 존재하는 경우 제안된 스위칭 다이나믹을 가진 제어 시스템의 응답은 일정 시간이 경과된 후 스위칭 평면의 임의의 영역으로 균일하게 유계된다는 것을 증명한다. 또한, 제어 입력의 크기에 대한 제약성을 만족하면서도 전체 제어 시스템의 정상 상태 오차를 감소시키기 위하여 두개의 스위칭 다이나믹을 도입한 수정된 슬라이딩 모드제어기를 제안한다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제12권3호
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• pp.215-224
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• 2012

This paper deals with a design of fault tolerant state feedback controllers for continuous time nonlinear time delay systems with actuator failures. The goal is to find an asymptotically stabilizing controller such that the closed loop system achieves the prescribed $H_{\infty}$ performance objective in the actuator fault cases. Based on a sum of squares (SOS) approach, a design method for $H_{\infty}$ fault tolerant controller is presented. In order to demonstrate our design method, a numerical example is provided.

• International Journal of Control, Automation, and Systems
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• 제5권1호
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• pp.70-78
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• 2007

We prove that TCP Vegas globally converges to its equilibrium point in finite time assuming no feedback information delay. We analyze a continuous-time TCP Vegas model with discontinuity and high nonlinearity. Using the upper right-hand derivative and applying the comparison lemma, we cope with the discontinuous signum function in the TCP Vegas model; using a change of state variables, we deal with the high nonlinearity. Although we ignore feedback information delay in analyzing the model of TCP Vegas, the simulation results illustrate that TCP Vegas in the presence of feedback information delay shows very similar dynamic trends to TCP Vegas without feedback information delay. Consequently, dynamic properties of TCP Vegas without feedback information delay can be used to estimate those of TCP Vegas in the presence of feedback information delay.

• 제어로봇시스템학회논문지
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• 제2권3호
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• pp.209-219
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• 1996

Fieldbus provides a real-time data communication among field devices in the process control and manufacturing automation systems. In this paper, a Petri Net model of the 1993 draft of IEC/ISA fieldbus which is proposed as an international standard of fieldbus network is developed. Based on the Petri Net model, discrete-event simulation model of IEC/ISA fieldbus network is developed. This paper evaluates the network induced delay in the data link layer of IEC/ISA fieldbus using the simulation model. In addition, an integrated discrete-event/continuous-time simulation model of fieldbus system and distributed control system is developed. This paper investigates the real-time data processing capability of IEC/ISA fieldbus and the effect of network-induced delay to the performance of control system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.858-863
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• 1990

A synthesis of feedback control-law with combined H$_{2}$/H$_{\infty}$ perfoemance criteria is proposed for discrete-time systems, under the assumption that the state is available for feedback. An auxiliary minimization problem is defined to enforce the H$_{\infty}$ disturbance attenuation constrain while minimizing the H$_{2}$ performance bound. The design equation is presented in terms of a modified Riccati equation which leads to the standard LQ solution when the H$_{\infty}$ constraint is completely relaxed. The results of the paper clarity the correspondences between H$_{2}$/H$_{\infty}$ results in discrete-time systems and their continuous-time counter-parts.rts.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.125-129
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• 1987

The stability margin of the LQ regulator is investigated in the time domain. it is shown that the same guaranteed gain margin as that of the frequency domain analysis can be obtained with simple assumptions for the continuous time systems. It is also shown that the allowable modelling error bound can be expressed in terms of system matrices and Riccati equation solution. Guaranteed qain. margin and the allowable modelling error bound for the discrete time systems are also obtained by the similar procedures. In this case, through the some examples, the gain margin is shown to be less conservative than the frequency domain analysis result.

• 대한전기학회논문지:전력기술부문A
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• 제55권1호
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• pp.13-17
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• 2006

In this paper, the RCF(Resistive Companion Form) analysis method which is used to analyze small signal stability problems of non-continuous systems including switching devices. The RCF analysis method is mathematically rigorous and computes eigenvalue of the system periodic transition matrix based on discrete system analysis method. As an effect of switching operations, the eigenvalues of the systems are changed and newly unstable oscillation modes may be occurred. As an illustrating example, the oscillation modes of the system with different switching time intervals are computed exactly by the RCF analysis method and the results show that ON/OFF time intervals of switching equipments are important factors to make the system stable or unstable. This result shows that the RCF analysis method is very powerful to analyze small signal stability problems of power systems including switching devices such as FACTS equipments.