• Journal of applied mathematics & informatics
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• 제33권5_6호
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• pp.687-697
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• 2015

This paper shows that the solutions to the perturbed nonlinear functional differential system

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.721-723
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• 1987

An Adaptation algorithm is presented and a convergence criterion is derived for parallel model reference adaptive bilinear systems. The output error converges asymptotically to zero, and the parameter estimates are bounded for stable reference models. The convergence criterion depends only upon the input sequence and a priori estimates of the maximum parameter values.

• Journal of applied mathematics & informatics
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• 제28권3_4호
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• pp.797-804
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• 2010

The aim of this paper is to investigate the global stability, periodic nature, oscillation and the boundedness of solutions of the difference equation $x_{n+1}\;=\;\frac{A+Bx_{n-1}}{C+Dx_n^2}$, n = 0, 1, 2, ... where A, B are nonnegative real numbers and C, D > 0.

• 전력전자학회논문지
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• 제4권2호
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• pp.138-143
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• 1999

본 논문에서는 직접 구동용 브러쉬 없는 직류 전동기(BLDD)에 있어서 외란에 강인한 위치 제어를 하기 위한 새로운 제어 방법으로 적응 제어형 외란 관측기를 제시하였다. 정밀 위치 제어를 위해서 Field-orientation 방법을 통해 선형화 하였다. BLDC 전동기는 뒤틈(backlash)이 없는 반면에 높은 가격과 비선형 특성에 의한 복잡한 제어기가 필요하다는 단점이 있다. 또한 외부 외란은 전동기의 축에 직접 영향을 미치고 있다. 이 외란은 영향을 줄이기 위해서 Lyapunov 안정성 이론을 이용하였다. 이 이론을 바탕으로 제안된 시스템의 안정성을 증명하였으며, 관측기에서 취한 값을 순간적으로 등가 전류로 계산하여 정궤환(feedforward)하여 보상하였다.

• 대한수학회지
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• 제49권4호
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• pp.779-794
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• 2012

In this paper, we study the global stability of two mathematical models for human immunodeficiency virus (HIV) infection with intra-cellular delays. The first model is a 5-dimensional nonlinear delay ODEs that describes the interaction of the HIV with two classes of target cells, $CD4^+$ T cells and macrophages taking into account the saturation infection rate. The second model generalizes the first one by assuming that the infection rate is given by Beddington-DeAngelis functional response. Two time delays are used to describe the time periods between viral entry the two classes of target cells and the production of new virus particles. Lyapunov functionals are constructed and LaSalle-type theorem for delay differential equation is used to establish the global asymptotic stability of the uninfected and infected steady states of the HIV infection models. We have proven that if the basic reproduction number $R_0$ is less than unity, then the uninfected steady state is globally asymptotically stable, and if the infected steady state exists, then it is globally asymptotically stable for all time delays.

• 전기학회논문지
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• 제60권11호
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• pp.2139-2146
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• 2011

In this paper, a robust adaptive controller is proposed for trajectory tracking of robot manipulators with the unknown friction coefficient and bounded disturbance. A new adaptive control law is developed based on sliding mode and derived from the Lyapunov stability analysis. The introduction of a boundary layer solves the problem of chattering. The proposed adaptive controller is globally asymptotically stable and guarantees zero steady state error for joint positions. The estimated friction coefficients can also approach the actual coefficients asymptotically. A simulation example is provided to demonstrate the performance of the proposed algorithm.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제1권1호
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• pp.44-49
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• 2001

For minimum phase systems, the conventional fuzzy logic controllers (FLCs) use the error and the change-of-error as fuzzy input variables. Then the control rule table is a skew symmetric type, that is, it has UNLP (Upper Negative and Lower Positive) or UPLN property. This property allowed to design a single-input FLC (SFLC) that has many advantages. But its control parameters are not automatically adjusted to the situation of the controlled plant. That is, the adaptability is still deficient. We here design a single-input direct adaptive FLC (SDAFLC). In the AFLC, some parameters of the membership functions characterizing the linguistic terms of the fuzzy rules are adjusted by an adaptive law. The SDAFLC is designed by a stable error dynamics. We prove that its closed-loop system is globally stable in the sense that all signals involved are bounded and its tracking error converges to zero asymptotically. We perform computer simulations using a nonlinear plant and compare the control performance between the SFLC and the SDAFLC.

• 대한수학회논문집
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• 제34권2호
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• pp.685-699
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• 2019

This research is focused on a continuous epidemic model of transmission of Plasmodium vivax malaria with a time delay. The model is represented as a system of ordinary differential equations with delay. There are two equilibria, which are the disease-free state and the endemic equilibrium, depending on the basic reproduction number, $R_0$, which is calculated and decreases with the time delay. Moreover, the disease-free equilibrium is locally asymptotically stable if $R_0<1$. If $R_0>1$, a unique endemic steady state exists and is locally stable. Furthermore, Hopf bifurcation is applied to determine the conditions for periodic solutions.

• 한국수자원학회논문집
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• 제46권5호
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• pp.491-504
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• 2013

본 연구에서는 shelf 지형을 대상으로 불규칙파를 적용한 2차원 쇄파변형 수리실험과 Boussinesq형 방정식을 이용한 수치해석을 수행하였다. 유의파고, 유의파봉고, 유의파곡고, 평균수위 및 안정파고와 같은 쇄파특성을 수리실험자료로부터 분석하였고, 실험결과와 Boussinesq형 방정식의 해석결과를 비교하였으며, 두 결과는 비교적 잘 일치하였다. 일정수심상에서의 불규칙파의 쇄파후 안정파고는 수심의 약 0.56배로 분석되었다.

• 대한수학회보
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• 제44권3호
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• pp.439-445
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• 2007

The aim of this work is to investigate the global stability, periodic nature, oscillation and the boundedness of solutions of the difference equation $$x_{n+1}={\frac{Ax_{n-1}}{B+Cx_{n-2}{\iota}x_{n-2k}$$, n = 0, 1, 2,..., where A, B, C are nonnegative real numbers and $\iota$, k are nonnegative in tegers, $\iota{\leq}k$.