• Journal of the Korean Society for Precision Engineering
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• v.21 no.9
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• pp.48-55
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• 2004

This study presents a genetic algorithm-based method fur optimizing control parameters in the pressure control of electro-hydraulic pump with variable displacement. Genetic algorithms are general-purpose optimization methods based on natural evolution and genetics and search the optimal control parameters maximizing a measure that evaluates the performance of a system. Four control gains of the PI-PD cascade controller for an electro-hydraulic pressure control system are optimized using a genetic algorithm in the experiment. Optimized gains are confirmed by inspecting the fitness distribution which represents system performance in gain spaces. It is shown that genetic algorithm is an efficient scheme in optimizing control parameters of the pressure control of electro-hydraulic pump with variable displacement.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.2
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• pp.165-174
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• 2007

Variable displacement type piston pump uses various controllers for controlling more than one state quantity like pressure, flow, power, and so on. These controllers need the mathematical model closely expressing dynamic behavior of pump for analyzing the stability of control systems which usually use various kinds of state variables. This paper derives the nonlinear mathematical model for variable displacement type piston pump. This model consists of two 1st oder differential equations by the continuity equations and one 2nd oder differential equation by the motion equation. To simplify the model we obtain the linear state variable model by differentiating the three nonlinear equations. And we verify this linearized model by comparison of simulation with experimentation and analyze the stability for the flow/pressure control. Finally this paper suggests the design compensation to ensure the stability of the systems.

• Earthquakes and Structures
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• v.19 no.2
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• pp.129-144
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• 2020

In this study, the idea of damping force linearly proportional to horizontal isolation displacement is implemented into sloped rolling-type bearings in order to meet different seismic performance goals. In addition to experimentally demonstrating its practical feasibility, the previously developed analytical model is further modified to be capable of accurately predicting its hysteretic behavior. The numerical predictions by using the modified analytical model present a good match of the shaking table test results. Afterward, several sloped rolling-type bearings designed with linearly variable damping force are numerically compared with a bearing designed with conventional constant damping force. The initial friction damping force adopted in the former is designed to be smaller than the constant one adopted in the latter. The numerical comparison results indicate that when the horizontal isolation displacement does not exceed the designed turning point (or practically when subjected to minor or frequent earthquakes that seldom have a great displacement demand for seismic isolation), the linearly variable damping force design can exhibit a better acceleration control performance than the constant damping force design. In addition, the former, in general, advantages the re-centering performance over the latter. However, the maximum horizontal displacement response of the linearly variable damping force design, in general, is larger than that of the constant damping force design. It is particularly true when undergoing a horizontal isolation displacement response smaller than the designed turning point and designing a smaller value of initial friction damping force.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.721-724
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• 2002

This study deals with a dynamic behavior analysis of pump control regulator varied the swash plate tilting angle with the positive and negative direction. To accomplish it's purpose, modeling and displacement response analysis about principal parts (spool, servo piston, feedback lever, sleeve) of pump control regulator was performed. We have been able to verifying the propriety of servo mechanism and design parameters of pump control regulator by research results. So, it respect to utilized with useful research data at variable displacement control valve development of variable displacement piston pump.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.305-315
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• 1986

Redesign of the mounting system to minimize vibration of a variable displacement engine through computer simulation is considered. A three degree of freedom model is established for an in-line four-cylinder automobile engine with a three point mounting system. The engine mount locations and angles, and isolator sizes are chosen as design parameters. Constraints on isolator deformations and design parameters are imposed. The gradient projection method is utilized for optimization. Simulation studies show significant vibration reduction can be obtained especially at idling speed.

• Structural Engineering and Mechanics
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• v.11 no.4
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• pp.443-460
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• 2001

This paper presents an effective application of a variable-node axisymmetric solid element designated as AQV (Axisymmetric Quadrilateral Variable-node element). The variable-node element with physical midside nodes helps to overcome some problems in connecting the different layer patterns on a quadrilateral mesh in the adaptive h-refinement. This element alleviates the necessity of imposing displacement constraints on irregular (hanging) nodes in order to enforce the inter-element compatibility. Therefore, the elements with variable mid-side nodes can be used effectively in the local mesh refinement for the axisymmetric structures which have stress concentrations. A modified Gaussian quadrature should be adopted to evaluate the stiffness matrices of the variable-node elements mainly because of the slope discontinuity of assumed displacement within the elements. Some numerical examples show the usefulness of variable-node axisymmetric elements in the practical application.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.387-388
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.385-386
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• 2008

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.1 no.1
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• pp.65-74
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• 1997

For two dimensional elasticity, we suggest a new complex variable method using the Navier's displacement equation. This method gives alternative displacement and stress formulae to those resulting from the Muskhelishvili's complex function method.

• Korean Journal of Mathematics
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• v.7 no.2
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• pp.245-269
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• 1999

Multigrid method and acceleration by conjugate gradient method for first-order system least squares (FOSLS) using bilinear finite elements are developed for various boundary value problems of planar linear elasticity. They are two-stage algorithms that first solve for the displacement flux variable, then for the displacement itself. This paper focuses on solving for the displacement flux variable only. Numerical results show that the convergence is uniform even as the material becomes nearly incompressible. Computations for convergence factors and discretization errors are included. Heuristic arguments to improve the convergences are discussed as well.