• International Journal of Control, Automation, and Systems
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• 제6권1호
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• pp.24-34
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• 2008

A novel neural network model, termed the standard neural network model (SNNM), similar to the nominal model in linear robust control theory, is suggested to facilitate the synthesis of controllers for delayed (or non-delayed) nonlinear systems composed of neural networks. The model is composed of a linear dynamic system and a bounded static delayed (or non-delayed) nonlinear operator. Based on the global asymptotic stability analysis of SNNMs, Static state-feedback controller and dynamic output feedback controller are designed for the SNNMs to stabilize the closed-loop systems, respectively. The control design equations are shown to be a set of linear matrix inequalities (LMIs) which can be easily solved by various convex optimization algorithms to determine the control signals. Most neural-network-based nonlinear systems with time delays or without time delays can be transformed into the SNNMs for controller synthesis in a unified way. Two application examples are given where the SNNMs are employed to synthesize the feedback stabilizing controllers for an SISO nonlinear system modeled by the neural network, and for a chaotic neural network, respectively. Through these examples, it is demonstrated that the SNNM not only makes controller synthesis of neural-network-based systems much easier, but also provides a new approach to the synthesis of the controllers for the other type of nonlinear systems.

• Journal of Communications and Networks
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• 제9권3호
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• pp.219-228
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• 2007

In this paper, we present a novel blind adaptive multiuser detector structure and three robust recursive filters to improve the performance in CDMA environments: Sigma point kalman filter (SPKF), particle filter (PF), and Gaussian mixture sigma point particle filter (GMSPPF). Our proposed robust recursive filters have superior performance over a conventional extended Kalman filter (EKF). The proposed multiuser detector algorithms initially use Kalman prediction form to estimated channel parameters, and unknown data symbol be predicted. Second, based on this predicted data symbol, the robust recursive filters (e.g., GMSPPF) is a refined estimation of joint multipaths and time delays. With these estimated multipaths and time delays, data symbol detection is carried out (Kalman correction form). Computer simulations show that the proposed algorithms outperform the conventional blind multiuser detector with the EKF. Also we can see it provides a more viable means for tracking time-varying amplitudes and time delays in CDMA communication systems, compared to that of the EKF for near-far ratio of 20 dB. For this reason, it is believed that the proposed channel estimators can replace well-known filter such as the EKF.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1136-1141
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• 2004

This paper presents a control method for time-delay systems and verifies the performance of the designed control system via real experiments. Specifically, the control method is applied to a flexible-link system with time delays. The method combines time- and frequency-domain controllers: linear quadratic optimal controller (or LQR) and lag compensator. The LQR is used to stabilize the system in optimal fashion, whereas the lag compensator is used to compensate time-delay effects by increasing the delay margin of the system. With this methodology, the maximum allowable time delay can be increased significantly. The proposed method is simple but quite practical for time-delay system control as it is based on the conventional loop-shaping method, which gives practical insights on delay-phase relationship. Simulation and experiment results show that the method presented in this paper is feasible and practical.

• 제어로봇시스템학회논문지
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• 제14권8호
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• pp.792-799
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• 2008

Motion estimation is crucial in a remote control for its convenience or accuracy. Time delays, however, can occur in the problem because data communication is required through a network. In this paper, state estimation problem with uncertain time delayed measurements is addressed. In dynamic system with noise, after taking measurements, it often requires some time until that is available in the filter algorithm. Standard filters not considering this time delays cannot be used since the current measurement is related with a past state. These delayed measurements are solved with augmented extended Kalman filter, and the uncertainty of delayed time is also resolved based on an explicit formulation. The proposed method is analyzed and verified by simulations.

• 대한전기학회논문지:전력기술부문A
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• 제48권10호
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• pp.1287-1292
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• 1999

In large-scale systems, we frequently encounter the time-delay and the uncertainty, and these should be considered in the design of controller because these are the source of the degradation of the system performance and instability of system. In this paper, we consider the robust stability of the linear large scale systems with the uncertainties and the time-delays. The considered uncertainties are both structured uncertainty and the unstructured uncertainty. Also, the considered time-delays are time-varying having finite time derivative limits. Based on the Lyapunov theorem and the linear matrix inequality(LMI) technique, we present two sufficient conditions that guarantee the robust stability of the system. The conditions are expressed as the LMI forms which can be easily checked their feasibility by using the well-known LMI control toolbox. Finally, we show by two examples that our results are less conservative than the previous results.

• 제어로봇시스템학회논문지
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• 제14권6호
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• pp.554-557
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• 2008

We analyze the stability property of a class of nonlinear time-delay systems with time-varying delays. We present a time-delay independent sufficient condition for the global asymptotic stability. In order to prove the sufficient condition, we exploit the inherent property of the considered systems instead of applying the Krasovskii or Razumikhin stability theory that may cause the mathematical difficulty of analysis. We prove the sufficient condition by constructing two sequences that represent the lower and upper bound variations of system state in time, and showing the two sequences converge to an identical point, which is the equilibrium point of the system. The simulation results illustrate the validity of the sufficient condition for the global asymptotic stability.

• 한국건설관리학회논문집
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• 제16권3호
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• pp.165-176
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• 2015

국내 건설산업의 침체가 장기화됨에 따라 대형 건설업체를 중심으로 국내사업 비중이 줄고 상대적으로 해외사업의 비중이 증가되고 있으며, 중견 건설업체 및 특수기술을 가지고 있는 전문건설업체의 해외프로젝트 수행이 확대되고 있다. 이러한 해외건설공사 수행의 중요성이 부각되고 있는 최근 상황에서 해외 대형건설공사에서 일반적으로 발생되고 있는 공기지연에 대한 적극적 대응이 성공적 프로젝트관리의 중요한 이슈로 제기되고 있다. 본 연구에서는 해외 대형프로젝트의 공기지연 클레임의 공기연장기간을 입증하는데 활용되는 기존 공기연장기간 분석방법의 실무적 적용상의 문제점을 제기하였다. 제시된 문제점을 해결하기 위한 개선방법으로 1)클레임의 명확성을 확보하기 위해 지연영향력 분석이전에 주요지연(dominant delay)를 선정하는 절차를 갖는 개선개념과 2)Time Impact Analysis을 시행을 위한 분석구간의 설정방법에 대한 개선개념을 제시하였다. 본 연구에서 제시한 공기연장기간 분석방법을 실제 해외 대형건설공사의 공기지연 클레임 사례에 적용함으로써, 제안한 개선안의 실무적용에 대한 유효성을 입증하였다. 국내의 해외 대형공사 공기지연 클레임을 담당하고 있는 기술자들이 본 연구에서 제안한 방법들을 공기지연 클레임 추진 및 관련자 협상 등과 같은 실무 추진에 참고하고 활용함을 통해, 공기연장기간 입증관련 클레임의 협상실패로 인한 리스크와 후속적인 분쟁 및 회사의 경영손실 리스크를 최소화 하는데 도움이 될 것이라고 사료된다.

• 한국건설관리학회논문집
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• 제24권1호
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• pp.12-20
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• 2023

국내에서 관행적으로 사용되어온 간편법에 의한 공기지연 분석시 발주자와 계약자의 지연일수 산정은 동시발생 공기지연의 영향과 돌관공사의 수행의 영향을 반영하지 못하는 한계가 있으며, 양 당사자에 대한 지체상금의 부과에 있어서도 문제를 가져왔다. 본 연구에서는 지체상금에 대한 국제 판례를 분석하고, 발주자와 계약자의 지연일수의 비율을 적용하여 지체상금을 부과하는 기존 방식의 문제점을 국제 기준과 비교하여 분석되었다. 공기지연 분석의 문제점과 이를 기반으로 한 지체상금 산정의 문제점을 개선하기 위해서는 공기지연 분석에 있어서 발주자 지연, 계약자 지연, 동시발생 공기지연을 분석하고, 돌관공사의 영향을 고려한 종합적인 공기지연에 대한 귀책 분석이 필요하며, 지체상금의 부과에 있어서 발주자의 귀책에 의한 지연일수와 동시발생 공기지연 일수를 합한 기간 만큼 준공기한을 연장하고, 그 이후에 발생된 지연에 대하여 지체상금을 부과하는, 국제기준에 부합하는 지체상금 부과 방안을 제시하였다. 본 연구의 결과는 기존 관행적으로 수용되어 오던 실무 공기지연분석 및 지체상금 산정의 문제점을 개선하는데 기여할 수 있을 것으로 기대된다.

• Transactions on Control, Automation and Systems Engineering
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• 제2권1호
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• pp.19-23
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• 2000

In this paper, we deal with the problem of designing guaranteed cost state feedback controller for the generalized time-varying delay systems with delayed state and control input. The generalized time delay system problems solved on the basis of LMI(linear matrix inequality) technique considering time-varying delays. The sufficient condition for the existence of controller and guaranteed cost state feedback controller design methods are presented. Also, using some changes of variables and Schur complements, the obtained sufficient condition can be reformulated as LMI forms in terms of transformed variables. Therefore, all solutions of LMIs, guaranteed cost controller gain, and guaranteed cost are obtained at the same time. The proposed controller design method can be extended into the problem of robust guaranteed cost controller design method for parameter uncertain systems with time-varying delays easily.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.886-891
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• 2003

This paper deals with designing a ground-based longitudinal landing controller which is robust to datalink time delays. Time delays occur because forward velocity measurements are downlinked and the controller output commands are uplinked. An $H_{\infty}$ controller was designed by using the input/output decomposition where time delay is modeled as a first-order system with Pade approximation. Linear simulations show that the system tracks well the predefined path and is robust to the variation of time delay.