• International Journal of Fuzzy Logic and Intelligent Systems
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• v.4 no.2
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• pp.199-204
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• 2004

In this paper, a new dual-rate digital control technique for the Takagi-Sugeno (T-S) fuzzy system is suggested. The proposed method takes account of the stabilizablity of the discrete-time T-S fuzzy system at the fast-rate sampling points. Our main idea is to utilize the lifted control input. The proposed approach is to obtain the dual-rate discrete-time T-S fuzzy system by discretizing the overall dynamics of the T-S fuzzy system with the lifted control, and then to derive the sufficient conditions for the stabilization in the sense of the Lyapunov asymptotic stability for this system. An example is provided for showing the feasibility of the proposed discretization method.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1289-1294
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• 2003

This paper proposes a novel and efficient intelligent digital redesign technique for a Takagi-Sugeno (TS) fuzzy system. The term of intelligent digital redesign involves converting an existing analog fuzzy-model-based controller into an equivalent digital counterpart in the sense of state matching. In this paper, we suggest the discretization method based on the dual-rate sampling approximation is first proposed, and then attempt to globally match the states of the overall closed-loop TS fuzzy system with the pre-designed analog fuzzy-model-based controller and those with the digitally redesigned fuzzy-model-based controller. To show the feasibility and the effectiveness of the proposed method, a computer simulation is provided.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.1
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• pp.33-44
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• 1993

Active control of a flow field is essential to design efficient parts or elements relating to fluid machineries. The present study is aimed to suggest a new discretization technique of the convection term by renewing the non-conservative equation found in SOLA-VOF into a conservative one. And, as an application, flow characteristics are investigated by adjusting the backward ejecting velocity of 2-D square prism to control the aerodynamic properties. Strouhal number, drag and lift coefficient are compared in terms of various ejecting velocity. Among the results, the transient weak fluctuation of the lift and drag coefficient when the ejecting velocity equals channel inlet velocity is remarkably noticed.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.3
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• pp.149-155
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• 2009

A new finite element equation is derived by applying quadratic and cubic time integration scheme to the variational formulation in time-integral for the analysis of the transient elastodynamic problems to increase the numerical accuracy and stability. Emphasis is focused on methodology for cubic time integration scheme procedure which are never presented before. In this semidiscrete approximations of the field variables, the time axis is divided equally and quadratic and cubic time variation is assumed in those intervals, and space is approximated by the usual finite element discretization technique. It is found that unconditionally stable numerical results are obtained in case of the cubic time variation. Some numerical examples are given to show the versatility of the presented formulation.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.5
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• pp.24-33
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• 2003

This study proposed a technique for inverse problem, linear approximation of contact position and loading in single and double meshing of transmission contact element using 2-dimension model considered near the tooth by root stress. Determination of root stress is carried out far the gear tooth by finite element method and boundary element method. Boundary element discretization near contact point is carefully performed to keep high computational accuracy. The predicted results of boundary element method are good accordance with that of finite element method.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.666-670
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• 2008

The low-speed preconditioning technique is applied to solve the compressible Reynolds averaged Navier-Stokes equations for low-speed flows. The space discretization is based on Roe's flux-difference splitting with third-order-accurate MUSCL extrapolation. Time integration is performed employing a diagonal approximate factorization algorithm. The dual-time stepping has been incorporated to solve the unsteady flows. Full multigrid method is implemented to accelerate the convergence rate. To verify the algorithms several cases have been tested. Demonstrated the improvement on convergence and quality of the solution.

• Steel and Composite Structures
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• v.51 no.3
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• pp.261-270
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• 2024

This paper proposes an effective method for optimizing the structure of functionally graded isotropic and incompressible linear elastic materials. The main emphasis is on utilizing a specialized polytopal composite finite element (PCE) technique capable of handling a broad range of materials, addressing common volumetric locking issues found in nearly incompressible substances. Additionally, it employs a continuum model for bi-directional functionally graded (BFG) material properties, amalgamating these aspects into a unified property function. This study thus provides an innovative approach that tackles diverse material challenges, accommodating various elemental shapes like triangles, quadrilaterals, and polygons across compressible and nearly incompressible material properties. The paper thoroughly details the mathematical formulations for optimizing the topology of BFG structures with various materials. Finally, it showcases the effectiveness and efficiency of the proposed method through numerous numerical examples.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.684-689
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• 2001

In this study, three-dimensional viscous flow analysis and optimization are presented for the design of a mixed-flow fan. Steady, imcompressible, three-dimensional Reynolds averaged Navier-Stokes equations are used as governing equations, and standard $k-{\varepsilon}$ turbulence model is chosen as a turbulence model. Governimg equations are discretized using finite volume method. Upwind difference scheme is used for the discretization of the convective term and SIMPLEC algorithm is used as a velocity-pressure correction procedure. The computational results are compared with the results obtained by TASCflow. For the numerical optimization of the design, objective function is defined as a ratio of generation of the turbulent energy to pressure head. Sweep angles are used as design variables.

• Journal of KSNVE
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• v.9 no.4
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• pp.813-821
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• 1999

This paper presents the technique using wavelet analysis to solve the seismic response of a steam turbine-generator rotor system subjected to earthquake excitations. A brief review of the wavelet transform and its discretization, time-frequency representation of the earthquake wave and the seismic response for a rotor system is presented. The Daubechies wavelet has been used for describing the time-frequency characteristics of the input and the response in case of a recorded accelerogram during 1995 Hyogoken Nanbu earthquake. Also, the results in the wavelet domain has been illustrated through comparison with the time domain simulation results.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2543-2545
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• 2004

In this paper, a new multirate digital control technique for the Takagi-Sugeno (T-S) fuzzy system is suggested. The proposed method takes account of the stabilizablity of the discrete-time T-S fuzzy system at the fast-rate sampling points. Our main idea is to utilize the lifted control input. The proposed approach is to obtain the multirate discrete-time T-S fuzzy system by discretizing the overall dynamics of the T-S fuzzy system with the lifted control, and then to derive the sufficient conditions for the stabilization in the sense of the Lyapunov asymptotic stability for this system. An example is provided for showing the feasibility of the proposed discretization method.