• 대한전기학회논문지
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• 제37권11호
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• pp.753-761
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• 1988

Partial Matrix Refactorization (PR) has been available for refactorization repeatedly. But this paper aims to present Modified PR(MPR), which is faster in (re) factorization speed and simpler in program than PR, but storage is almost as big as that of PR. MPR substitutes refactorization process of PR1 for Modifide Trifactortzation (MT) and, instead of PR 2, adds to PR1 the algoritm that calculates modified element values of modified row / cols. MT, which is subalgorithm for MPR, simplifies the algorithm by applying information vectors to currently used Trifactorization, and trifactorizes and refactorizes in high speed. The test results of Fast Decoupled Load Flow (FDLF) and Contingency Analysis useing Indexing Scheme and Optimal Ordering also prove that MPR is faster than PR.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.231-235
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• 1988

In this paper we present a new method to control system design using a sliding mode. The objective of this research is to develop the algorithm for the sliding mode control which is able to remove the chattering phenomena and to reduce the reaching phase. To accomplish this approach we introduce switching dynamics instead of switching logics to obtain the sliding mode. Consequently, we can obtain the new design approach which is much simpler than the VSS theory. And there do not exist chattering phenomena in this method because the obtained control input are continuous. Simultaneously we can reduce the reaching phase by a suitable choice of design factor. Numerical examples are discussed as illustration.

• 한국전산유체공학회지
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• 제15권3호
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• pp.87-94
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• 2010

Hydromagnetic flow in a cavity under a uniform magnetic field is studied numerically. The cavity is comprised of four radiatively active surfaces. Due to large temperature difference inside a cavity, the radiative interaction between walls is taken into account. The coupled momentum and energy equations are solved by SIMPLER algorithm while the radiant heat exchanges are obtained by the finite volume method for radiation. A Wide range of Grashof numbers is examined as a controlling parameter. Resultant flow and heat transfer characteristics are investigated as well.

• 유변학
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• 제2권1호
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• pp.33-45
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• 1990

This study analyzes the planar 4:1 contraction flow of viscoelastic fluids with retardation time using finite volume method. To consider separately the elasticity effect of the viscoelastic fluid without shear thinn-ing effect, Oldroyd B liquid model is adopted for the numerical simulation. Instead of the stream function-vorticity formulation, SIMPLER algorithm with staggered grid system which incorporates primitive variable has been introduced in discretizing the momentum equations. An upwind corrected scheme has been used in discetizing the constitutive equations for the non-Newtonian part of the stress. The size of the corner vortex is shown to be slightly influenced by the Weissenberg number. However as the Weissenberg number is increased the chang-ing of the vortex shape agrees qualitatively well with some experimental studies.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제22권2호
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• pp.125-136
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• 2018

In this article, a homotopy perturbation transform method (HPTM) and the Laplace transform combined with Taylor expansion method are presented for solving Volterra integral equations with a convolution kernel. The (HPTM) is innovative in Laplace transform algorithm and makes the calculation much simpler while in the Laplace transform and Taylor expansion method we first convert the integral equation to an algebraic equation using Laplace transform then we find its numerical inversion by power series. The numerical solution obtained by the proposed methods indicate that the approaches are easy computationally and its implementation very attractive. The methods are described and numerical examples are given to illustrate its accuracy and stability.

• Transactions on Control, Automation and Systems Engineering
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• 제4권4호
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• pp.253-263
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• 2002

This paper presents an adaptive feedback linearization control scheme for induction motors using stator fluxes. By using stator flukes as states, overparameterization is prevented and control inputs can be determined straightforwardly unlike in existing schemes. This approach leads to the decrease of the relative degree for the flux modulus and thus yields a simpler control algorithm than the prior results. In this paper. adaptation schemes are suggested to compensate for the variations of stator resistance. rotor resistance and load torque. In particular, the adaptation to the variation of stator resistance with a feedback linearization control is a new trial. In addition, to improve the convergence of rotor resistance estimation, the differences between stator currents and its estimates are used for the parameter adaptation. The simulations show that torque and flux are controlled independently and that the estimates of stator resistance, rotor resistance, and load torque converge to their true values. Actual experiments on a 3.7㎾ induction motor verify the effectiveness of the proposed method.

• 산업기술연구
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• 제6권
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• pp.39-48
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• 1986

This paper examines the effects on safety index analysis with Level II Second-Moment Method. The general two variable problem is examined by means of Cornell safety index ${\beta}c$ Rosenblueth-Esteva safety index ${\beta}_{RE}$ Rackwitz-Fiessler safety index by iterative method and Practical FOSM safety index ${\beta}_p$, which based partly on the concepts given by Paloheimo and Hannus, proposed the algorithm in this paper. The calculated examples have shown that safety index by Practical FOSM Method proposed in this paper would be similar to those in the method by Rosenblueth-Esteva or Rackwitz-Fissler and be simpler in calculation than the Rackwitz's Advanced FOSM Method, in which the iterative procedure has to be used.

• 전기학회논문지
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• 제65권6호
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• pp.1089-1094
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• 2016

In order to establish the robust controller design technique of series wound motor driver system. This paper proposes a method of Bang-Bang controller using a series wound motor driver system under improperly variable load. A Bang-Bang controller structure is simpler than the structure of PID plus Bang-Bang controller. This paper shows that a general 8 bits microprocessor is used efficiently implementing such an algorithm. The calculation time of software is extremely small when compared with conventional PID plus Bang-Bang controller. Both nonlinear operating characteristics of digital switching elements and describing function methods are used for the analysis and synthesis. Real time implementation of Bang-Bang controller is achieved. Concept design strategy of the control and PWM waveform generation algorithms are presented in the paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.661-662
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• 2008

In this paper a novel bearingless switched reluctance motor (BLSRM) with hybrid stator poles is proposed. The operating principle of the proposed motor is presented. Further one prototype motor is designed and manufactured. Compared with existing BLSRM, it has many advantages such as lower number of switches and cost, simpler control algorithm, lower thermal load. Meanwhile through finite element method (FEM) characteristics of the proposed structure such as inductance, torque and radial force can be obtained. According to the FEM results, the above advantages of the proposed structure can be verified.

• 한국전산유체공학회지
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• 제14권3호
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• pp.123-130
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• 2009

Hydromagnetic flow in a confined enclosure under a uniform magnetic field is studied numerically. The thermally active side walls of the enclosure are kept at hot and cold temperatures specified, while the top and bottom walls are insulated. The coupled momentum and energy equations associating with the electromagnetic retarding force as well as the buoyancy force terms are solved by an iterative procedure using the SIMPLER algorithm based on control volume approach. The changes in the flow and thermal field based on the orientation of an external magnetic field, which varies from 0 to $2{\pi}$ radians, are investigated. Resulting heat transfer characteristics are examined too.