• 제어로봇시스템학회논문지
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• 제13권2호
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• pp.147-153
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• 2007

The stability robustness problem of linear discrete-time systems with delayed time-varying perturbations is considered. Compared with continuous time system, little effort has been made for the discrete time system in this area. In the previous results, the bounds were derived for the case of non-delayed perturbations. There are few results for delayed perturbation. Although the results are for the delayed perturbation, they considered only the time-invariant perturbations. In this paper, the sufficient conditions for stability can be expressed as linear matrix inequalities(LMIs). The corresponding stability bounds are determined by LMI(Linear Matrix Inequality)-based algorithms. Numerical examples are given to compare with the previous results and show the effectiveness of the proposed results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.972-975
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• 1996

This paper presents a sufficient condition for robust stability of discrete-time systems with delayed nonlinear perturbations. Using state evolution method, the bound on the norms of nonlinear perturbation which guarantees the exponential stability of the systems, is found. The numerical example is given to illustrate the results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.31.5-31
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• 2001

In conventional perturbation estimators such as disturbance observers(DOB) [1, 2] or time-delayed controllers(TDC) [3{5}, the low pass filter(so-called Q-filter) plays an important role in the stability and performance. However, a general design guideline or analysis for the Q-filter has not been researched yet. In this paper, a guideline for the design of discrete Q-filter is suggested in terms of the analysis of the relationship between the filter parameters and stability performance robustness in discrete-time domain. The analysis clarifies the discrete-time effect of the perturbation estimator and provides a transparent relationship between performance and robustness depending ...

• Journal of applied mathematics & informatics
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• 제27권5_6호
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• pp.1097-1107
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• 2009

In this paper, three species stage-structured predator-prey model with time delayed and periodic constant impulsive perturbations of predator at fixed times is proposed and investigated. We show that the conditions for the global attractivity of prey(pest)-extinction periodic solution and permanence of the system. Our model exhibits a new modelling method which is applied to investigate impulsive delay differential equations. Our results give some reasonable suggestions for pest management.

• 제어로봇시스템학회논문지
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• 제11권11호
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• pp.901-906
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• 2005

The stability robustness problem of continuous linear systems with nominal and delayed time-varying perturbations is considered. In the previous results, the entire bound was derived only for the overall perturbations without separation of the perturbations. In this paper, the sufficient condition for stability of the system with two perturbations, which are nominal and delayed, is expressed as linear matrix inequalities(LMIs). The corresponding stability bounds fer those two perturbations are determined by LMI(Linear Matrix Inequality)-based generalized eigenvalue problem. Numerical examples are given to compare with the previous results and show the effectiveness of the proposed.

• Journal of applied mathematics & informatics
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• 제40권3_4호
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• pp.491-505
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• 2022

This paper is concerned with singularly perturbed convection-diffusion parabolic partial differential equations which have time-delayed. We used the Crank-Nicolson(CN) scheme to build a fitted operator to solve the problem. The underling method's stability is investigated, and it is found to be unconditionally stable. We have shown graphically the unstableness of CN-scheme without fitting factor. The order of convergence of the present method is shown to be second order both in space and time in relation to the perturbation parameter. The efficiency of the scheme is demonstrated using model examples and the proposed technique is more accurate than the standard CN-method and some methods available in the literature, according to the findings.

• 한국전산유체공학회지
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• 제20권2호
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• pp.73-80
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• 2015

Delayed Detached-Eddy Simulation was conducted to investigate surface pressure coefficient distribution and surface pressure fluctuation over an ONERA 70-degree delta wing at a high angle of attack. Time-averaged surface pressure distribution is directly affected by the primary vortices, whereas the pressure fluctuation is influenced by the unsteady fluctuating boundary layer over the surface. And pressure coefficient, velocity, pressure fluctuation, and turbulent kinetic energy were analyzed along the vortex core in order to investigate the process of vortex breakdown. Consequently, strong pressure fluctuations were found where the vortex breakdown was occurred at x~620 mm. The turbulent kinetic energy abruptly increased and followed after the vortex breakdown.

• 한국전문물리치료학회지
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• 제14권2호
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• pp.21-28
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• 2007

The purpose of this study was to compare the onset times of muscle activities and the order of muscle firing in erector spinae, multifidus, rectus abdominis and biceps brachii during perturbation between subjects with and without work-related chronic low back pain (LBP). Twenty-nine subjects, 14 with and 15 without LBP, participated in this study. The muscle responses were measured by surface EMG (electromyography) during perturbation in eye opened and eye closed conditions. The EMG onset times of the erector spinae, multifidus, rectus abdominis and biceps brachii were similar between groups in eye closed condition. But the onset times of the erector spinae, multifidus, rectus abdominis were significantly delayed in subjects with LBP in eye opened condition. The results provide an evidence for impaired feed-forward control of the trunk muscles in subjects with LBP. Further studies are needed to identify whether the impaired feed-forward control of the trunk muscles is the contributing factor to LBP.

• 재활복지
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• 제14권3호
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• pp.225-256
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• 2010

본 연구는 초등학교 지적장애아동의 자세조절 특성을 파악하기 위해 시각, 안뜰감각 그리고 몸감각을 조합하여, 실험 조건에 따라 자세유지를 위하여 어떤 감각을 활용하고 있는지, 부적절한 감각자극에 대해서 통합시스템에서 어떻게 반응하는지, 외부 동요에 대해 신경근육의 자세조절 전략 시 동원되는 근육의 수축 개시시간과 개시순서를 각각 측정하여, 지적장애 아동의 자세조절 특성을 살펴보고, 나아가 초등학교 지적장애아동과 일반아동 간에 어떠한 차이가 있는지를 비교분석하여 자세조절능력 향상 프로그램에 적용 시 방향을 제시해주는데 있다. 이를 위하여 성별과 연령을 고려하여 초등학교 지적장애아동 26명과 일반아동 26명의 아동으로부터 자세조절능력을 비교하였다. 그 결과 자세조절과 감각계와의 관계를 파악한 평형점수와 감각활용 분석, 엉덩관절 전략에 의지하는 자세조절 전략, 근수축 개시지연과 근수축 개시순서의 변화 등을 종합해 볼 때 초등학교 지적장애아동의 자세조절의 문제는 운동시스템, 감각시스템, 통합시스템의 자세조절 시스템 전반에 걸친 총체적인 문제로 나타났다. 따라서 초등학교 지적장애아동의 자세조절 문제 해결을 위해서는 운동시스템, 감각시스템, 통합시스템을 포함하는 포괄적 자세조절 훈련 프로그램의 접근이 필요하다는 것을 알 수 있다. 자세조절 프로그램을 구성할 때, 다양한 감각을 제공하여 주고, 제공된 감각을 효율적으로 활용할 수 있는 감각훈련과 함께 고위중추에서 입력된 감각들을 정상적인 자세조절 발달에 활용할 수 있도록 훈련 시켜주어야 한다. 적응 반응을 계획하고 조직화하여 의미 있는 활동을 통해 중추신경계의 처리능력을 향상시키는 치료프로그램이 제공되어야 한다. 또한 자세조절을 안정적으로 할 수 있는 안정성 한계를 넓힐 수 있는 신경발달학적 치료와 함께, 근골격계에서 빠른 근수축 반응과 효율적인 근수축 개시순서를 유발 할 수 있도록 고유수용성 운동조절 프로그램, 자세반응 촉진 프로그램과 같은 훈련이 필요하다고 할 수 있다.