• 전기학회논문지
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• 제57권10호
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• pp.1854-1860
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• 2008

In this paper, we deal with the problem of delay-dependent robust and non-fragile stabilization for descriptor systems with parameter uncertainties and time-varying delays on the basis of strict LMI(linear matrix inequality) technique. Also, the considering controller is composed of multiplicative uncertainty. The delay-dependent robust and non-fragile stability criterion without semi-definite condition and decomposition of system matrices is obtained. Based on the criterion, the problem is solved via state feedback controller, which guarantees that the resultant closed-loop system is regular, impulse free and stable in spite of all admissible parameter uncertainties, time-varying delays, and controller fragility. Numerical examples are presented to demonstrate the effectiveness of the proposed method.

• International Journal of Control, Automation, and Systems
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• 제5권1호
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• pp.8-14
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• 2007

This paper describes a robust and non-fragile $H_{\infty}$ controller design method for descriptor systems with parameter uncertainties and time delay, as well as a static state feedback controller with multiplicative uncertainty. The controller existence condition, as well as its design method, and the measure of non-fragility in the controller are proposed using linear matrix inequality(LMI) technique, which can be solved efficiently by convex optimization. Therefore, the presented robust and non-fragile $H_{\infty}$ controller guarantees the asymptotic stability and disturbance attenuation of the closed loop systems within a prescribed degree in spite of parameter uncertainties, time delay, disturbance input and controller fragility.

• 한국통신학회논문지
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• 제13권4호
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• pp.352-359
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• 1988

학습제어 시스템은 제어대상 시스템의 파라미터를 모르는 경우에 파라미터 적응의 개념을 도입해서, 일종의 hybrid형 적응제어 시스템으로 간주하여 설계될 수 있다. 이러한 파라미터 적응형 학습제어 시스템은 이미 보고되었으나 연속시간 시스템에만 적용될 수 있었다. 본 논문에서는 메모리소자를 반드시 포함하여야 하는 학습시스템에 대하여, 위의 제어알고리즘을 이산화 함으로써 디지탈기술의 발전에 비추어 실제의 적용을 용이하도록 하였으며, 그 타당성을 시뮬레이션으 통하여 확인하였다.

• Journal of Power Electronics
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• 제16권1호
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• pp.1-8
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• 2016

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.

• 대한전자공학회논문지
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• 제24권1호
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• pp.20-27
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• 1987

The hierarchical approach method is proposed to sperate each different time scale sub-systems from linear time invariant multi-parameter singular perturbation systems. By means of this proposal, the original multi-parameter singular perturbation systems is completely separated into independent subsystems with each different time scale. It is also investigated that the controllability of the system is invariant. And this paper applies singular perturbation methods to the minimum control effort problem for linear time invariant systems with constrained controls. Also near-optimum control theory, which is based on dividing the total time interval with the time scales respectively, is proposed. As a result, the time scale separation method is show to be particularly useful in a near optimum design which can be otained through a decentralized control structure.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2000년도 추계학술대회 논문집(Proceeding of the KOSME 2000 Autumn Annual Meeting)
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• pp.135-142
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• 2000

The adjusting parameter set which enable control systems to locate on stability limit can be derived from theoretical or trial methods for an existing real system. The data from the results are much available to keep a system in the Proper stability condition even to site engineers who are inexperienced in the control system. In this paper, a general one loop control system was adopted for a model system the process of which was assumed to consist of a time-delay element and a first order-lag element in series. After obtaining the corresponding parameter set for the model system by mathematical procedures, their loci on the parameter space was taken according to frequency change. The parameter set loci of stability limit showed unique pattern, and particularity , the curves on the Kg-Ti parameter space were able to be generalized in the form of, an unique exponential formula. These properties were also compared with the results taken from experimental procedures by Nyquist response method and Ziegler & Nichols method on the time domain, and both results were confirmed to be nearly same.

• 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.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제18권3호
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• pp.257-268
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• 2014

The objective of the present study is to investigate thermal diffusion and radiation effects on unsteady MHD flow past a linearly accelerated vertical porous plate with variable temperature and also with variable mass diffusion in presence of heat source or sink under the influence of applied transverse magnetic field. The fluid considered here is a gray, absorbing/emitting radiation but a non-scattering medium. At time t > 0, the plate is linearly accelerated with a velocity $u=u_0t$ in its own plane. And at the same time, plate temperature and concentration levels near the plate raised linearly with time t. The dimensionless governing equations involved in the present analysis are solved using the closed analytical method. The velocity, temperature, concentration, skin-friction, the rate or heat transfer and the rate of mass transfer are studied through graphs in terms of different physical parameters like magnetic field parameter (M), radiation parameter (R), Schmidt parameter (Sc), Soret number (So), Heat source parameter (S), Prandtl number (Pr), thermal Grashof number (Gr), mass Grashof number (Gm) and time (t).

• 한국항공우주학회지
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• 제32권9호
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• pp.57-64
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• 2004

본 논문은 실제의 비행시험 데이터를 이용하여 커나드 비행기 Velocity-173의 가로-방향의 조종/안정 미계수들을 추정하는 것이며, 나아가서 비행중에 (In-Flight) 실시간 파라미터 추정기법을 이용한 미계수 확인 및 분석에 관한 내용이다. 본 논문에서 적용한 비행 중 실시간 파라미터 추정기법의 결과는 AAA의 해석 결과와 비교하였으며, 그 결과는 상당히 신뢰할 수 있고 계산시간 또한 만족스러움을 확인하였다.

• 조명전기설비학회논문지
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• 제24권8호
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• pp.84-93
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• 2010

이 논문은 이산신호가 연속적으로 입력될 때, 이산신호에서 고속으로 파라미터를 추정하고, 그 결과를 시각화하는 방법에 대해서 기술하고 있다. 이 논문은 이산푸리에변환에서 직접 파라미터를 추정하는 고속파라미터 추정 알고리즘을 적용하여 연속신호에서 파라미터를 추정하고, 추정한 중요 파라미터들을 효율적으로 시각화하는 방법에 대해서 기술하고 있다. 이 논문에서 제안한 연속신호에 대한 저주파 파라미터 추정방법을 3개의 모드를 가진 시험함수에 적용하여 제안한 알고리즘과 시각화의 효율성을 검증하였다.