• Proceedings of the KSME Conference
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• 2008.11a
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• pp.436-441
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• 2008

One of important factors in designing array-type MEMS resonators is obtaining a desired frequency response function (FRF) within a specific range. In this paper Krylov subspace-based model order reduction using moment-matching with non-zero expansion points is represented to calculate the FRF of array-type resonators. By matching moments at a frequency around a specific range of the array-type resonators, required FRFs can be efficiently calculated with significantly reduced systems regardless of their operating frequencies. In addition, because of the characteristics of moment-matching method, a minimal order of reduced system with a specified accuracy can be determined through an error indicator using successive reduced models, which is very useful to automate the order reduction process and FRF calculation for structural optimization iterations.

• Journal of applied mathematics & informatics
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• v.24 no.1_2
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• pp.399-409
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• 2007

In this paper we use iterative dynamic programming in the discrete case to solve a wide range of the nonlinear equations systems. First, by defining an error function, we transform the problem to an optimal control problem in discrete case. In using iterative dynamic programming to solve optimal control problems up to now, we have broken up the problem into a number of stages and assumed that the performance index could always be expressed explicitly in terms of the state variables at the last stage. This provided a scheme where we could proceed backwards in a systematic way, carrying out optimization at each stage. Suppose that the performance index can not be expressed in terms of the variables at the last stage only. In other words, suppose the performance index is also a function of controls and variables at the other stages. Then we have a nonseparable optimal control problem. Furthermore, we obtain the path from the initial point up to the approximate solution.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.4
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• pp.54-60
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• 2009

Weight reduction of automobile parts has been sought to achieve fuel efficiency and energy conservation. In this study, a shape design procedure is suggested to obtained the lightweight design of an outer tie rod. The developed aluminium Al6082M is selected as a steel-substitute material. Strength assesment and durability are the important design criterion in the structural design of an outer tie rod. This study considers strength and durability in the optimization process. In this study, the kriging interpolation method and trial and error method are adopted to obtain the minimum weight satisfying the strength and durability constraints.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.6
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• pp.538-548
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• 2014

This study provides a robust control of a grid-connected three-phase two-level photo voltaic inverter. The introduced control method uses the cascade control strategy to regulate AC-side current and DC-link voltage. A robust controller with integration action is used for the inner-loop AC-side current control, which maximizes the convergence rate using a linear matrix inequality-based optimization design method and eliminates the offset error. The robust controller design method considers the parameter uncertainty set to accommodate parameter mismatch and un-modeled components in the inverter model. An outer-loop proportional-integral controller is used to regulate DC-link voltage with linearization of DC/AC relation. The proposed control strategy is applied to a grid-connected 100 kW photo voltaic inverter.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.10
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• pp.101-108
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• 1999

Most of researches for deep drawing process have been performed on the formability of axisymmetric blank, but there is an insufficient study on the formability of non-axisymmetric blank. In addition, the conventional blank shape has been determined by the trial-and-error method using industrial experience and post processing test. Therefore only approximated shape of the blank can be presented. In this study, the optimal blank shape and concrete drafting method in deep drawing process with biaxisymmetric elliptical shape is proposed. Through the deep drawing experiment, it is found that the optimal blank shape gives the most uniform thickness of the products in the first process

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.561-562
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• 2006

To enhance the precision and productivity of ultra precision aspheric surface micro lens, the development of ultra-precision grinding system and process for the aspheric surface micro lens are described. In the work reported in this paper, an ultra-precision grinding system for manufacturing the aspheric surface micro lens was developed by considering the factors affecting the grinding surface roughness and profile accuracy. This paper deals with mirror grinding of an aspheric surface micro lens by resin bonded diamond wheel and spherical lens of BK7. The optimization of grinding conditions on ground surface roughness and profiles accuracy is investigated using the design of experiments.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.4
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• pp.43-49
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• 2004

A spring-actuated linkage system is used to satisfy the desired opening and closing characteristics of the electric contacts of a vacuum circuit breaker. If the type of a circuit breaker and the structure of the linkage system are predetermined, then design parameters such as stiffness, free length and attachment points of the spring become the important issues. In this paper, based on the energy conservation, the total system energy is constant throughout the operating range of the mechanism; a systematic procedure to optimize the spring design parameters is developed and applied to a simplified mechanism of a circuit breaker. The developed procedure is converted to the environment of the multi-body dynamics program, ADAMS for an in-depth consideration of the complex dynamics of a circuit breaker mechanism.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.8
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• pp.130-137
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• 1999

The criteria for determining the elements are the minimum zone method(MZM) and the least squares method(LSM). The LSM is deterministic and simple but is limited at the measurements whose errors are significant compared with form errors. For the precise condition, minimum zone method(MZM) has been selected to determine the elements. It is not deterministic and nonlinear so that a optimizing procedure is needed. The Straightness is the fundamental problem in the evaluating form error. In this paper, a new approach adapting the genius education concept is proposed to obtain an accurate results for the minimum zone problem of the straightness. Its computational algorithm is studied on a set of randomly generated data. To be of almost no account of the specification(the number and the standard devistion etc.) of the sample data, the results shows excellent reliability and high accuracy in estimating the straightness.

• Journal of Information Technology Services
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• v.7 no.2
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• pp.127-135
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• 2008

The concept of preprocessing is widely used in various computer science area such as compiler and software engineering for the purpose of macro processing and optimization. In addition, preprocessing is also used in SAT solvers in order to eliminate redundant literals and clauses to speed up its solving time before searching the state space. However, there is an unexpected run-time error such as stack-overflow during this step, in case the size of a given set of clauses is huge which impedes SAT solvers. In this case, the preprocessing should be applied at the encoding time to optimize its size. In this paper this idea is applied to several Sudoku problems. As a result, significant improvements are obtained with respect to the number of variables and clauses as well as the solving time compared to the previous works.

• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.705-707
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• 1997

An optimal tuning algorithm of scaling factors is presented in this paper to automatically improve the performance of fuzzy controller. Especially, fuzzy controller has determined an moderate Scaling factor through trial and error. The presented method estimates automatically the optimal values of I/O scaling factors, using modified steepest descent method and this optimal tuning is for nonlinear input/output scaling factors. Simulation results verify the validity of the presented method.