• Journal of applied mathematics & informatics
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• 제29권3_4호
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• pp.813-829
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• 2011

In this article, we present a numerical scheme for solving singularly perturbed (i.e. highest -order derivative term multiplied by small parameter) Burgers-Huxley equation with appropriate initial and boundary conditions. Most of the traditional methods fail to capture the effect of layer behavior when small parameter tends to zero. The presence of perturbation parameter and nonlinearity in the problem leads to severe difficulties in the solution approximation. To overcome such difficulties the present numerical scheme is constructed. In construction of the numerical scheme, the first step is the dicretization of the time variable using forward difference formula with constant step length. Then, the resulting non linear singularly perturbed semidiscrete problem is linearized using quasi-linearization process. Finally, differential quadrature method is used for space discretization. The error estimate and convergence of the numerical scheme is discussed. A set of numerical experiment is carried out in support of the developed scheme.

• 대한전기학회논문지
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• 제39권2호
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• pp.133-141
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• 1990

In the operation of an electric power system, the voltage security of the system has acquired more significant importance after the occurrence of large system black-outs caused by voltage collapse several times. This paper describes a fast contingency screening method concerning voltage security. The method defines a voltage-sensitive buses where significant voltage changes would occur as a result of the contingency to reduce the number of bus voltages to be solved for continngency screening. This method is based on the observation that it is not necessary to solve the entire network in most contingency cases because boltage changes actually occur around the contingency. The P-Q decoupled linearized model and the fast error correction method are also adopted in the method to define voltage-sensitive buses and to calculate voltage magnitude on the selected voltage-sensitive buses fastly and reliably. The method suggested in this papaer has been tested in IEEE 30-bus model system and KEPCO 130-bus actual system and its effectiveness for practical use has also been confirmed.

• 대한전기학회논문지
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• 제39권2호
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• pp.199-209
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• 1990

In this paper, a multivariable robust controller for a boiler-burbine system is designed by using a modified LQG/LTR method. From the known nonlinear dynamic model, a linearized model is obtained with the saturations at both input magnitude and input varying rate. The modeling error is analyzed at various operation points. A new dynamics augmentation method in the LQG/LTR method is suggested which can be applied to LQG/LTR method to reject the input and output disturbances and to follow reference inputs under modeling errors. The good performance of the designed controller is shown by simulations in various conditions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.136-136
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• 2000

The direct drive servo valve(DDV) is composed of a DC rotor, link, valve spool and displacement sensor(LVDT) where the spool is directly coupled to the DC motor through the link. Since the DDV is a kind of one-stage valve, the robust controller is required to overcome the flow force effect on the spool motion. The mathematical equations are derived and the stability, accuracy and response speed of a DDV are investigated analytically using a linearized system block diagram. Proportional control, PID control. Time-Delay control, Sliding Mode control, and Proportional control using the load pressure are applied to DDV to find which one shows the best control performance. The digital computer simulation results show that the proportional control using the load pressure satisfies the design requirement of response speed and steady state error regardless of the variation of load pressure,

• 한국정밀공학회지
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• 제25권12호
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• pp.82-88
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• 2008

This paper describes an application of sliding mode control to an active magnetic bearing(AMB) system. A sliding mode control is robust to model uncertainties and external disturbances. To ensure the authority of sliding mode control, model parameter uncertainties caused from linearization of electro-magnetic attractive force are analyzed and a domain of parameter uncertainties in which reachability to sliding surface is guaranteed is derived. The validity of the analysis is illustrated along with some simulation examples.

• 대한전기학회논문지
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• 제34권12호
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• pp.491-497
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• 1985

An applicaton of the linear optimal control theory to the problem or load follow control in pressurized water reactors (PWR) is investigated. In order to perform the steady-state and load follow operation in PWR, a nonlinear model for the reactor and steam generator is derived and linearized at 50% rated power. Simulation tests are performed for 10% demanded load. Comparing the dynamic response of the newly developed optimal load follow controller with those of the integral error feedback controller proposed by Yang, the rise time of dynamic response of the former is about 15 seconds faster than those of the latter, thus the results indicate that the fast response of the optimal load follow controller is verified. The results of this work are directly applicable to the design of the load follow control systems for commercially operated PWRs.

• 한국정밀공학회지
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• 제12권6호
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• pp.145-151
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• 1995

The first-order Taylor series expansion can be evaluated analytically from the formulated symbolic nonlinear dynamic equations. A closed-form linear dynamic euation is derived about a nominal trajectory. The state space representation of the linearized dynamics can be derived easily from the closed-form linear dynamic equations. But manual symbolic expansion of dynamic equations and linearization is tedious, time-consuming and error-prone. So it is desirable to manipulate the procedures using a computer. In this paper, the analytic linearization is performed using the symbolic language MATHEMATICA. Two examples are given to illustrate the approach anbd to compare nonlinear model with linear model.

• 대한수학회지
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• 제61권4호
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• pp.621-657
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• 2024

In this study, the numerical solution of a space-fractional Burgers' equation with initial and boundary conditions is considered. This equation is the simplest nonlinear model for diffusive waves in fluid dynamics. It occurs in a variety of physical phenomena, including viscous sound waves, waves in fluid-filled viscous elastic pipes, magneto-hydrodynamic waves in a medium with finite electrical conductivity, and one-dimensional turbulence. The proposed QBS/CNG technique consists of the Galerkin method with a function basis of quadratic B-splines for the spatial discretization of the space-fractional Burgers' equation. This is then followed by the Crank-Nicolson approach for time-stepping. A linearized scheme is fully constructed to reduce computational costs. Stability analysis, error estimates, and convergence rates are studied. Finally, some test problems are used to confirm the theoretical results and the proposed method's effectiveness, with the results displayed in tables, 2D, and 3D graphs.

• 한국통신학회논문지
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• 제28권1C호
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• pp.72-80
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• 2003

본 논문은 멀티패스 페이딩이 존재하는 CDMA 채널에서 새로운 빔형성 알고리즘을 통해 적응 배열 안테나의 성능을 향상시키기 위한 최적의 웨이트 벡터를 구하는 방법을 제시하였다. 제안한 빔형성 알고리즘은 멱승법을 근간으로 하며, 전체 계산량이 O(4N)밖에 되지 않는 선형화 된 멱승법(power method) 알고리즘이다. 여기서 N은 안테나 수를 의미한다. 제안된 알고리즘의 성능은 IS-2000 1X CDMA 환경에서 심볼 에러율(symbol error rate), 사용 가능자수(allowable capacity), 수렴도(convergence) 등에 대한 분석을 통해 확인하였다. 성능분석 결과 적응 배열 안테나 시스템은 기지국 셀 내에서 기존 안테나 시스템에 비해 6-10배정도 사용 가능자수가 증가하였다. 또한, 제안 알고리즘은 심볼 에러율, 수렴도, 계산량의 모든 경우에서 기존 알고리즘에 비해 우수한 성능을 보임을 확인하였다.

• 한국농공학회지
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• 제34권2호
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• pp.73-84
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• 1992

The TIDE, finite element model for the simulation of tidal flow in shallow sea was tested for its applicability at the Saemangeum area. Several pre and post processors were developed to facilitate handling of the complicated and large amount of input and output data for the model developed. Also an operation scheme to run the model and the processors were established. As a result of calibration test using the observed data collected at 9 points within the region, linearlized friction coefficients were adjusted to be ranged 0.0027~0.0072, and water depths below the mean sea level at every nodes were changed to be increased generally by 1 meter. Comparisons of tidal velocities between the observed and the simulated for the 5 stations were made and obtained the result that the average relative error between simulated and observed tidal velocities was 11% for the maximum velocities and 22% for the minimum, and the absolute errors were less than 0.2m/sec. Also it was found that the average R.M.S. error between the velocities of observed and simulated was 0.119 m/sec and the average correlation coefficient was 0.70 showing close agreement. Another comparison test was done to show the result that R.M.S. error between the simulated and the observed tidal elevations at the 4 stations was 0.476m in average and the correlation coefficients were ranged 0.96~0.99. Though the simulated tidal circulation pattern in the region was well agreed with the observed, the simulated tidal velocities and elevations for specific points showed some errors with the observed. It was thought that the errors mainly due to the characteristics of TIDE Model which was developed to solve only with the linearized scheme. Finally it was concluded that, to improve the simulation results by the model, a new attempt to develop a fully nonlinear model as well as further calibration and the more reasonable generation of finite element grid would be needed.