• 한국통신학회논문지
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• 제29권10C호
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• pp.1370-1377
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• 2004

시간 지연이 있는 시스템에서의 최적 제어 이득은 시간 지연이 없는 시스템에서 설계된 최적 제어 이득과 지연 시간에 대하여 계산된 상태천이 함수의 곱의 형태로 나타난다. 따라서 시간 지연이 없는 시스템에 대하여 PID제어기의 영점들을 플랜트의 최대 극점에 근접하도록 가중치 요소 Q와 R을 선택하여 최적 제어 이득을 구하고, 시간 지연이 있는 2차 시스템에서의 상태천이 함수를 계산하여 시간 지연이 있는 시스템에서의 강인한 최적 PID 제어기 설계가 가능하도록 하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 춘계학술대회 논문집
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• pp.469-470
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• 2010

• 대한수학회지
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• 제49권4호
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• pp.715-731
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• 2012

This paper considers the stability of positive steady-state solutions bifurcating from the trivial solution in a delayed Lotka-Volterra two-species predator-prey diffusion system with a discrete delay and subject to the homogeneous Dirichlet boundary conditions on a general bounded open spatial domain with smooth boundary. The existence, uniqueness and asymptotic expressions of small positive steady-sate solutions bifurcating from the trivial solution are given by using the implicit function theorem. By regarding the time delay as the bifurcation parameter and analyzing in detail the eigenvalue problems of system at the positive steady-state solutions, the asymptotic stability of bifurcating steady-state solutions is studied. It is demonstrated that the bifurcating steady-state solutions are asymptotically stable when the delay is less than a certain critical value and is unstable when the delay is greater than this critical value and the system under consideration can undergo a Hopf bifurcation at the bifurcating steady-state solutions when the delay crosses through a sequence of critical values.

• Transactions on Control, Automation and Systems Engineering
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• 제2권1호
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• pp.19-23
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• 2000

In this paper, we deal with the problem of designing guaranteed cost state feedback controller for the generalized time-varying delay systems with delayed state and control input. The generalized time delay system problems solved on the basis of LMI(linear matrix inequality) technique considering time-varying delays. The sufficient condition for the existence of controller and guaranteed cost state feedback controller design methods are presented. Also, using some changes of variables and Schur complements, the obtained sufficient condition can be reformulated as LMI forms in terms of transformed variables. Therefore, all solutions of LMIs, guaranteed cost controller gain, and guaranteed cost are obtained at the same time. The proposed controller design method can be extended into the problem of robust guaranteed cost controller design method for parameter uncertain systems with time-varying delays easily.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.246-248
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• 2006

This paper is concerned with non-fragile guaranteed cost state feedback controller design algorithm for descriptor systems with time-varying delay and static state feedback controller with multiplicative uncertainty. The considered uncertainties are norm-bounded and time delay is time-varying. Under the condition of controller gain variations, conditions for the existence of controller satisfying asymptotic stability and non-fragility and controller design method are derived via LMI approach. Moreover, the measure of non-fragility and the upper bound to minimize guaranteed cost function are given.

• JSTS:Journal of Semiconductor Technology and Science
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• 제1권3호
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• pp.193-196
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• 2001

For wide locking range, an analog delay locked loop (DLL) was designed with the selective phase inversion scheme and the variable number of delay elements. The number of delay elements was determined adaptively depending on the clock cycle time. During the analog fine locking stage, a self-initializing 3-state phase detector was used to avoid the initial state problem associated with the conventional 3-state phase detector. With these schemes, the locking range of analog DLL was increased by four times compared to the conventional scheme according to the simulation results.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1998년도 하계종합학술대회논문집
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• pp.239-242
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• 1998

Most of time delay existing in industrial processes can be modeled as an input time-delay which causes a lot of difficulties. To implement a time-delay free control, loop transfer function is recovered through the direct state feedback. For the proper state feedback, and observer is designed based upon the factorization approach which is known as one of the most powerful tool for the design of various control systems. The design scheme is parctically applied for the control of a DC motro which suffers from input time-delay. Simulational results demonstrate that this new algorithm guarantess the stability of the time-delayed system, as well as performance improvement compared to the conventional PI control.

• 제어로봇시스템학회논문지
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• 제14권11호
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• pp.1089-1093
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• 2008

This paper presents a robust state observer design for a class of Lipschitz nonlinear systems with time delay and external disturbance. Sufficient conditions on the existence of the proposed observer are characterized by linear matrix inequalities. It is also shown that the proposed observer design can reduce the effect on the estimation error of external disturbance up to the prescribed level in spite of the existence of time delay. Finally, a numerical example is provided to verify the proposed design method.

• 제어로봇시스템학회논문지
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• 제13권3호
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• pp.187-191
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• 2007

We analyze the stability property of a class of nonlinear time-delay systems. We show that the state variable is bounded both below and above, and the lower and upper bounds of the state are obtained in terms of a system parameter by using the comparison lemma. We establish a time-delay independent sufficient condition for the global asymptotic stability by employing a Lyapunov-Krasovskii functional obtained from a change of the state variable. The simulation results illustrate the validity of the sufficient condition for the global asymptotic stability.

• 전기학회논문지
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• 제59권10호
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• pp.1894-1899
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• 2010

This note is concerned with a robust sliding mode control(SMC) for a class of unmatched uncertain system with severe commensurate state time delay. The suggested method is extended to the control of severe state time delay systems with unmatched uncertainties except the matched input matrix uncertainty. A transformed sliding surface is proposed and a stabilizing control input is suggested. The closed loop stability together with the existence condition of the sliding mode on the proposed sliding surface is investigated through one Lemma and two Theorems by using the Lyapunov direct method with the concept of the control Lyapunov function instead of complex Lyapunov-Kravoskii functionals. Through an illustrative example and simulation study, the usefulness of the main results is verified.