• Journal of Institute of Control, Robotics and Systems
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• v.3 no.1
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• pp.17-22
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• 1997

The stability robustness problem of linear discrete-time systems with time-varying perturbations is considered. By using Lyapunov direct method, the perturbation bounds for guaranteeing the quadratic stability of the uncertain systems are derived. In the previous results, the perturbation bounds are derived by the quadratic equation stemmed from Lyapunov method. In this paper, the bounds are obtained by a numerical optimization technique. Linear matrix inequalities are proposed to compute the perturbation bounds. It is demonstrated that the suggested bound is less conservative for the uncertain systems with unstructured perturbations and seems to be maximal in many examples. Furthermore, the suggested bound is shown to be maximal for the special classes of structured perturbations.

• Journal of Institute of Control, Robotics and Systems
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• v.1 no.2
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• pp.78-82
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• 1995

In this paper, we consider the robustness analysis problem in state space models with linear time invariant perturbations. Based upon the discrete-time Lyapunov approach, sufficient conditions are derived for the eigenvalues of perturbed matrix to be located in a circle, and robustness bounds on perturbations are obtained. Spaecially, for the case of a diagonalizable hermitian matrix the bound is given in terms of the nominal matrix without the solution of Lyapunov equation. This robustness analysis takes account not only of stability robustness but also of certain types of performance robustness. For two perturbation classes resulting bounds are shown to be improved over the existing ones. Examples given include comparison of the proposed analysis method with existing one.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.303-306
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• 1996

We propose a robust tuning method of the quadratic criterion based iterative learning control(Q-ILC) algorithm for discrete-time linear batch system. First, we establish the frequency domain representation for batch systems. Next, a robust convergence condition is derived in the frequency domain. Based on this condition, we propose to optimize the weighting matrices such that the upper bound of the robustness measure is minimized. Through numerical simulation, it is shown that the designed learning filter restores robustness under significant model uncertainty.

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.356-361
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• 1986

This paper presents robustness properties of LQ regulators for input-delayed systems. Using frequency-domain representations, the Kalman inequality concerning the return-difference matrix is derived. The stability margins of LQ regulators are investigated using the Kalman inequality when the open-loop system is stable. In order to obtain stability margins a upper bound of the solution of LQ Riccati equations is derived. Finally, the LQG/LTR method to improve the robustness of LQG regulators is obtained and illustrated with an example.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.29B no.10
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• pp.46-52
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• 1992

This paper considers uncertain systems with closed-loop poles in a polygonal region. A method is presented which is applicable to computing the perturbation of a pole-located region due to parameter uncertainties. A method is also proposed to calculate the bound on parameter uncertainties which allow the closed-loop poles to remain in a specified region. They provide useful robustness measures on the closed-loop poles of uncertain systems.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.171-179
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• 2001

The purpose of this paper is the derivation and development of the new definitions and methods for the new estimation of robustness for the systems having structured uncertainties. This proposition adopts the theoretical analysis of the Lyapunov direct methods, that is, the sign properties of the Lyapunov function derivative integrated along finite intervals of time, in place of the original method of the sign properties of the time derivative of the Lyapunov function itself. This is the new sufficient criteria to relax the stability condition and is used to generate techniques for the robust design of control systems with structured perturbations. The systems considered are assumed to be nominally linear, with time-variant, nonlinear bounded perturbations. This new techniques demonstrate the improvement of robustness bounds from the numerical results.

• Journal of Communications and Networks
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• v.6 no.3
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• pp.226-234
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• 2004

This work presents a deterministic channel that rules according to inverse a power propagation law. The proposed channel model allows us to derive the lower bound and upper bound of packet's capture probability in Rayleigh fading and shadowing cellular mobile system. According to these capture probabilities, we analyze the system performance in the case of finite stations and finite communicated coverage of a base station. We also adopted a dynamic backoff window size to discuss the robustness of IEEE 802.11 draft standard. Some suggestions and conclusions from numerical results are given to establish the more strong CSMA/CA protocol.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.5
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• pp.827-837
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• 1994

This paper presents robustness propertis of the Kalman Fiter and the associated LQG/LTR method for linear time-invariant output-delayed systems. It is shown that, even for minimum phase plants, the LQG/LTR method can not recover the target loop transfer function. Instead, an upper bound on the recovery error is obtained using an upper bound of the solution of the Kalman filter Riccati equations. Finally, some dual properties between output-delayed systems and input-delayed systems are exploited.

• Journal of Korea Multimedia Society
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• v.16 no.5
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• pp.591-600
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• 2013

This paper addresses a feature-based robust watermarking scheme for digital images using a local invariant features of SURF (Speeded-Up Robust Feature) descriptor. In general, the feature invariance is exploited to achieve robustness in watermarking schemes, but the leakage of information about hidden watermarks from publicly known locations and sizes of features are not considered carefully in security perspective. We propose embedding and detection methods where the watermark is bound with circular areas and inserted into extracted circular feature regions. These methods enhance the robustness since the circular watermark is inserted into the selected non-overlapping feature regions instead of entire image contents. The evaluation results for repeatability measures of SURF descriptor and robustness measures present the proposed scheme can tolerate various attacks, including signal processing and geometric distortions.

• The Pure and Applied Mathematics
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• v.30 no.2
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• pp.191-201
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• 2023

In this paper the control system described by Urysohn type integral equation is studied. It is assumed that control functions are integrally constrained. The trajectory of the system is defined as multivariable continuous function which satisfies the system's equation everywhere. It is shown that the set of trajectories is Lipschitz continuous with respect to the parameter which characterizes the bound of the control resource. An upper estimation for the diameter of the set of trajectories is obtained. The robustness of the trajectories with respect to the fast consumption of the remaining control resource is discussed. It is proved that every trajectory can be approximated by the trajectory obtained by full consumption of the control resource.