• 제어로봇시스템학회논문지
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• 제11권1호
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• pp.13-18
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• 2005

This paper considers a design problem of the repetitive control system for linear systems with time-varying norm bounded uncertainties. Using the Lyapunov functional for time-delay systems, a sufficient condition ensuring robust stability of the repetitive control system is derived in terms of an algebraic Riccati inequality (ARI) or a linear matrix inequality (LMI). Based on the derived condition, we show that the repetitive controller design problem can be reformulated as an optimization problem with an LMI constraint on the free parameter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.618-620
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• 2005

An $H_2$ tracking controller is proposed for networked control systems. The network induced delay is assumed to be time varying and vary in the known range. The proposed controller guarantees stability and $H_2$ performance for all time varying delay in the known range. The proposed controller is verified using a simple networked motor control system.

• 전자공학회논문지SC
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• 제46권1호
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• pp.22-27
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• 2009

인터넷과 같은 네트워크 시스템에서 네트워크 혼잡, 대역폭, 거리에 따라 발생하는 시변 시간지연을 해결하는 것은 양방향 원격제어 시스템을 설계할 때 해결해야할 문제이다. 불규칙적인 시간 지연은 전체 시스템의 성능을 저하시키거나 불안정하게 만들 수 있기 때문이다. 이러한 안정성 문제를 해결하기 위해 양방향 원격 제어 시스템에서 수동성 이론이 사용되어져 왔다. 본 논문에서는 시간 지연의 변화율에 따라 전송 제어기에 시변 이득을 적용하여 수동성을 확보할 수 있는 알고리즘을 제안하였다. 그리고 시뮬레이션을 통해 제안한 시스템의 성능 결과를 보였다.

• 전기학회논문지
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• 제59권4호
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• pp.788-792
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• 2010

The problem of delay-dependent and parameter-dependent robust stability condition for discrete-time uncertain singular systems with polytopic uncertainty and interval time-varying delay is considered. A new robust stability condition based on parameter-dependent Lyapunov function is derived in terms of LMI (linear matrix inequality). Moreover, the proposed robust stability condition is a general condition for both singular and non-singular systems. A numerical example is presented to demonstrate the effectiveness of the proposed method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.113-116
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• 1997

In this paper, we present a robust $H^{\infty}$ controller design method for parameter uncertain time-varying systems with disturbance and that have time-varying delays in both state and control. It is found that the problem shares the same formulation with the $H^{\infty}$ control problem for systems without uncertainty. Through a certain differential Riccati inequality approach, a class of stabilizing continuous controller is proposed. For parameter uncertainties, disturbance and time varying delays, proposed controllers the plant and guarantee an $H^{\infty}$ norm bound constraint on disturbance attenuation for all admissible uncertainties. Finally a numerical example is given to demonstrate the validity of the results.ts.

• 제어로봇시스템학회논문지
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• 제2권2호
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• pp.81-87
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• 1996

Time delay control(TDC) law has been recently suggested as an effective control technique for nonlinear time-varying systems with uncertain dynamics and/or unpredictable disturbances. This paper focuses on the applications of the TDC algorithm to torque control of an engine system and speed control of an engine/automatic transmission system. Through the stability analysis of the engien system based on TDC, determination of the appropriate time delay and control factor is investigated. It was revealed that the size of time delay of the TDC law should be greater than that of transport delay of the system for both stability and better control performance. Simulation and experimental results for the engine torque control and engine/automatic transmission speed control systems show both relatively good command following and disturbance rejection properties. However, TDC controller shows rather slow responses when applied to the system with large transport delay.

• International Journal of Control, Automation, and Systems
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• 제6권1호
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• pp.1-14
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• 2008

This paper presents a convex optimization method for observer-based mixed $H_2/H_{\infty}$ control design of linear systems with time-varying state, input and output delays. Delay-dependent sufficient conditions for the design of a desired observer-based control are given in terms of linear matrix inequalities (LMIs). An observer-based controller which guarantees asymptotic stability and a mixed $H_2/H_{\infty}$ performance for the closed-loop system of the linear system with time-varying delays is then developed. A Lyapunov-Krasovskii method underlies the observer-based mixed $H_2/H_{\infty}$ control design. A numerical example with simulation results illustrates the effectiveness of the methodology.

• 전기학회논문지
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• 제63권4호
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• pp.502-508
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• 2014

In this paper, a delay-dependent $H_{\infty}$ filtering problem is investigated for discrete-time delayed nonlinear systems which include a more general sector nonlinear function instead of employing the commonly used Lipschitz-type function. By using the Lyapunov-Krasovskii functional approach, a less conservative sufficient condition is established for the existence of the desired filter, and then, the corresponding solvability condition guarantee the stability of the filter with a prescribed $H_{\infty}$ performance level. Finally, two simulation examples are given to show the effectiveness of the proposed filtering scheme.

• International journal of advanced smart convergence
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• 제9권3호
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• pp.137-140
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• 2020

Orthogonal time frequency space (OTFS) modulation is considered as one of the solutions to cope with high mobility channel environments. It converts the time-varying channel to the near-constant channel response in the delay-Doppler domain. This modulation scheme also benefits from the diversity in two-dimensional modulation. According to recent researches, this method outperforms the conventional OFDM modulation, especially in high-speed channel conditions. In this paper, to investigate the performance of OTFS in a practical system, channel estimation in the delay-Doppler domain is compared with the conventional method in the time-frequency domain at different mobile speeds. Simulation results confirm that the delay-Doppler domain channel estimation brings a better performance compared to the conventional one under the same overhead rate.

• 한국통신학회논문지
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• 제28권9A호
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• pp.684-693
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• 2003

본 논문에서는 시변 패킷 기반 무선 링크에서 메시지와 패킷의 전송 지연 시간을 분석하였다. 메시지는 베르누이(Bernoulli) 프로세스에 따라 도착하고 생성되는 메시지의 길이는 지수 분포를 가진다고 가정하였다. 또한 시간 변이성을 가지는 무선 링크의 특성을 반영하기 위하여 2-상태 마코프 모델을 사용하여 해석하였다. 이 마코프 모델로부터, 패킷의 도착율과 패킷 전송 서비스 시간, 무선 링크의 평균 PER(packet error rate)의 항으로 패킷의 평균 전송 지연 시간과 평균 큐 길이를 해석적으로 분석하였고, 이러한 패킷의 성능 지표들로부터 메시지의 전송지연 시간 및 큐 길이를 유도하였다. 수치적 결과로부터 시변 패킷 기반 무선 링크의 안정적 동작과 전송 성능을 보장하기 위해서는 PER에 따라 메시지 도착율 및 길이가 제한되어야 한다는 것을 알 수 있었다. 또한 성능에는 각 상태의 머무는 시간보다 PER의 영향이 큼을 알 수 있었다.