• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.391-395
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• 1990

A new control algorithm is developed to achieve the robust performance of the system during the overall control process. Time-varying sliding manifolds are proposed to remove the reaching phase which is one of common shortcomings of variable structure control scheme. A necessary and sufficient condition for the existence of a sliding mode on the newly proposed time-varying sliding mode on the newly proposed time-varying sliding manifolds is derived by Lyapunov's second method. The digital simulation results show that the newly proposed control algorithm is superior to the typical variable structure control algorithm with respect to the robust performance of the system. The simplicity of the proposed control algorithm encourages control engineers to implement the proposed control algorithm in many control problems.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.54 no.1
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• pp.17-25
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• 2005

This paper provides sufficient conditions for the robustness of Affine linear TFM(Transfer Function Matrix) MIMO (Multi-Input Multi-Output) uncertain systems based on Rosenbrock's DNA (Direct Nyquist Array). The parametric uncertainty is modeled through a Affine TFM MIMO description, and the unstructured uncertainty through a bounded perturbation of Affine polynomials. Gershgorin's theorem and concepts of diagonal dominance and GB(Gershgorin Bands) are extended to include model uncertainty. For this type of parametric robust performance we show robustness of the Affine TFM systems using Nyquist diagram and GB, DNA(Direct Nyquist Array). Multiloop PI/PB controllers can be tuned by using a modified version of the Ziegler-Nickels (ZN) relations. Simulation examples show the performance and efficiency of the proposed multiloop design method.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.7
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• pp.371-380
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• 2003

In this paper, a new design method of H$H_\infty$-Qn PSS using genetic algorithm(GA) is proposed to efficiently damp low frequency oscillations despite the uncertainties and various disturbances of power systems. The selection method of evaluation function is proposed for selecting the robust PSS parameters. All QFT boundaries are satisfied automatically and H$H_\infty$-norm is minimized simultaneously without trial and error procedure. The eigenvalues and the damping ratio of dominant oscillation mode are investigated to evaluate performance of designed controller for one machine infinite bus system. A disturbance attenuation performance is investigated through singular value bode diagram of the system. Dynamic characteristics are considered to verify robustness of the proposed PSS by means of nonlinear simulations under various disturbances for various operating conditions. The results show that the proposed PSS is more robust than conventional PSS.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.15 no.2
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• pp.96-101
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• 2015

Support vector machine (SVM) has a strong theoretical foundation and also achieved excellent empirical success. It has been widely used in a variety of pattern recognition applications. Unfortunately, SVM also has the drawback that it is sensitive to outliers and its performance is degraded by their presence. In this paper, a new outlier detection method based on genetic algorithm (GA) is proposed for a robust SVM. The proposed method parallels the GA-based feature selection method and removes the outliers that would be considered as support vectors by the previous soft margin SVM. The proposed algorithm is applied to various data sets in the UCI repository to demonstrate its performance.

• Phonetics and Speech Sciences
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• v.5 no.1
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• pp.11-16
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• 2013

This paper proposes robust feature extraction for accurate voice activity detection (VAD). VAD is one of the principal modules for speech signal processing such as speech codec, speech enhancement, and speech recognition. Noisy environments contain nonstationary noises causing the accuracy of the VAD to drastically decline because the fluctuation of features in the noise intervals results in increased false alarm rates. In this paper, in order to improve the VAD performance, harmonic-weighted energy is proposed. This feature extraction method focuses on voiced speech intervals and weighted harmonic-to-noise ratios to determine the amount of the harmonicity to frame energy. For performance evaluation, the receiver operating characteristic curves and equal error rate are measured.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.198-202
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• 2004

This thesis proposes a robust controller introducing the H$_{\infty}$ control theory, one of the robust control theories that can obtain desired control performance while ensuring robustness for the uncertainty and disturbance contained in the power system. The performance of the designed controller is examined by extensive non-linear time domain simulation. Results show that the proposed H$_{\infty}$ controller is superior to that of the conventional controller.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1179-1185
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• 2010

This paper deals with a robust controller design problem for a small one-link robot arm system subject to input time delay and load variations. The uncertain parameters of the system are considered as a disturbance input. A disturbance observer(DOB) has been designed to alleviate disturbance effects and to compensate performance degradation owing to the time-delay. This paper employs a new DOB structure for non-minimum phase systems together with the Smith predictor. We propose a new controller for reducing the both effects of disturbance and time-delay. In order to test the performance of proposed controller, four different other control laws are compared with the proposed one by computer simulations. The simulation results show the effectiveness of the proposed control method.

• International Journal of Automotive Technology
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• v.8 no.3
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• pp.351-359
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• 2007

In this study, a hierarchical switching control scheme based on robust control theory is proposed for tracking control of vehicle longitudinal acceleration in the presence of large uncertainties. A model set consisting of four multiplicative-uncertainty models is set up, and its corresponding controller set is designed by the LMI approach, which can ensures the robust performance of the closed loop system under arbitray switching. Based on the model set and the controller set, a switching index function by estimating the system gain of the uncertainties between the plant and the nominal model is designed to determine when and which controller should be switched into the closed loop. After theoretical analyses, experiments have also been carried out to validate the proposed control algorithm. The results show that the control system has good performance of robust stability and tracking ability in the presence of large uncertainties. The response time is smaller than 1.5s and the max tracking error is about $0.05\;m/S^2$ with the step input.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.11
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• pp.510-513
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• 2002

In this paper, the robust adaptive controller design scheme is studied for nonlinear systems in the presence of bounded disturbances A new robust adaptive controller is designed using high-order neural networks, which avoids the singularity problem in adaptive nonlinear control. The stability of the resulting adaptive system with the proposed adaptive controller si guaranteed by suitably choosing the design parameters and initial conditions. I addition, the proposed adaptive controller provides improved transient performance and fast on-line adaptation. The ability and effectiveness of the proposed adaptive control scheme is shown trough simulations of a simple nonlinear system.

• 제어로봇시스템학회:학술대회논문집
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• 1995.10a
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• pp.356-359
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• 1995

This paper uses a new method to improve the performance criterion of an active suspension car. The used control strategy is based on robust H$_{\infty}$ control theory taking into consideration the chasis flexibility. It will be shown that the modeling errors can be lumped into an unstructured uncertainty and the robust controller designed in the presence of these perturbations could maintain the stability and performance even for the controlled true system..