• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.175-178
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• 1998

Tracings streamlines in global coordinate, especially with finite element mesh, requires much computation due to C0 continuity of velocity field. In this study, a new approach is presented for the determination of streamlines from velocity field obtained by FE analysis. It is shown that amount of calculation can be drastically reduced and boundary of element can be easily treated. The approach is applied to the problem of free surface of deforming workpieces in shape rolling.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.345-345
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• 2000

This paper introduces a new design approach for robust sliding-mode control of a class of mismatched uncertainties. For this, we propose a design method of sliding-mode surface using eigenstructure assignment to be insensitive to perturbation in sliding-mode systems, and also find a formula which is shown bounds of mismatched uncertainties for stability of the system. Simulation results are given to illustrate the approach proposed in this paper.

• 대한조선학회지
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• 제27권1호
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• pp.3-10
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• 1990

선체형상의 수치적 표현방법에는 선형을 구성하고 있는 일련의 곡선들을 이용하여 선형을 표현하는 curve approach와 선형을 직접 surface로 수식 처리하여 선형을 정의하는 surface approach가 있다. 본 논문에서는 2차원 곡선인 transverse section curve와 3차원 곡선인 longitudinal curve로 구성되는 곡선군들에 의해 형성되는 곡면요소를 수학적으로 처리하여 선체형상을 정의하는 curve approach방법에 대해 기술하였다. 형상 표면에 사용된 곡선 형태는 일반적인 parametric cubic spline을 보완한 modified cubic spline으로서 이 spline형태는 곡선 segment의 양 끝점에서의 접선 각도가 클 경우에도 아주 부드러운 곡률 분포를 얻을 수 있게 하기 때문에 선박 계산뿐만 아니라 유체동역학적 계산을 위한 선형 정의용으로 사용 가능할 정도의 정확성을 가진 기본 설계용 선형정의 결과를 얻을 수 있었다. 응용 예로서 SWATH 선형과 해양 조사선 선형을 표현한 결과를 보였으며, 본 선형 정의 방법을 선형 변환 기법과 연결하여 설계 요구 조건에 적합한 선형을 얻기 위한 선형 변환 예도 보였다.

• Journal of Computational Design and Engineering
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• 제3권1호
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• pp.1-13
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• 2016

The increase of consumer needs for quality metal cutting related products with more precise tolerances and better product surface roughness has driven the metal cutting industry to continuously improve quality control of metal cutting processes. In this paper, two different approaches are discussed. First, design of experiments (DOE) is used to determine the significant factors and then fuzzy logic approach is presented for the prediction of surface roughness. The data used for the training and checking the fuzzy logic performance is derived from the experiments conducted on a CNC milling machine. In order to obtain better surface roughness, the proper sets of cutting parameters are determined before the process takes place. The factors considered for DOE in the experiment were the depth of cut, feed rate per tooth, cutting speed, tool nose radius, the use of cutting fluid and the three components of the cutting force. Finally the significant factors were used as input factors for fuzzy logic mechanism and surface roughness is predicted with empirical formula developed. Test results show good agreement between the actual process output and the predicted surface roughness.

• Structural Engineering and Mechanics
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• 제73권5호
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• pp.501-513
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• 2020

In the present work, the optimization of machining parameters to achieve the desired technological parameters such as surface roughness, tool radial vibration and material removal rate have been carried out using response surface methodology (RSM). The hard turning of EN19 alloy steel with coated carbide (GC3015) cutting tools was studied. The main problem faced in manufacturer of hard and high precision components is the selection of optimum combination of cutting parameters for achieving required quality of surface finish with maximum production rate. This problem can be solved by development of mathematical model and execution of experiments by RSM. A face centred central composite design (FCCD), which comes under the RSM approach, with cutting parameters (cutting speed, feed rate and depth of cut) was used for statistical analysis. A second-order regression model were developed to correlate the cutting parameters with surface roughness, tool vibration and material removal rate. Consequently, numerical and graphical optimization were performed to obtain the most appropriate cutting parameters to produce the lowest surface roughness with minimal tool vibration and maximum material removal rate using desirability function approach. Finally, confirmation experiments were performed to verify the pertinence of the developed mathematical models.

• 천문학회보
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• 제43권2호
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• pp.47.1-47.1
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• 2018

Solar cycles are inherent to the Sun, which experiences temporal changes in its magnetic activity via the surface distribution of the solar magnetic field. This raises a fundamental question of how to derive the distribution characteristics of a solar-surface magnetic field that are responsible for individual solar cycles. We present a new approach to deriving as long-term and large-scale distribution characteristics of this quantity as was ever obtained; that is, we conducted a population ecological analysis of Wilcox Solar Observatory (WSO) Synoptic Charts which provide a more than 40-year time series of latitude-longitude maps of solar-surface magnetic fields. In this approach, solar-surface magnetic fields are assumed as hypothetical trees with magnetic polarities (magnetic trees) distributed on the Sun. Accordingly, we identified a peculiarity of cycle 23 with a longer period than an average period of 11 years; specifically we found that the negative surface magnetic field had much more clumped distributions than the positive surface magnetic field during the first one-third of this cycle, while the latter was dominant over the former. The Sun eventually spent more than one-third of cycle 23 recovering from these imbalances.

• Industrial Engineering and Management Systems
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• 제7권3호
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• pp.197-203
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• 2008

Many quality engineering practitioners continue to have a considerable interest in implementing the concept of response surface methodology to real situations. Recently, dual response surface approach is extensively studied and recognized as a powerful tool for robust design. However, existing methods do not consider the information provided by customers and design engineers. In this regard, this article proposes a flexible optimization model that incorporates that information via desirability function modeling. The optimization scheme and its modeling flexibility are demonstrated through an illustrative example by comparing the proposed model with existing ones.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.125-125
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• 2000

An Empirical approach to determine a road-surface condition is presented The road-surface condition thus provided includes the detection of not only friction coefficient, but also abrupt surface-profile changes such as pitfalls and bumpers The former plays a key role in establishing the appropriate control strategy, while the latter allows to minimize unnecessary brake intervention induced by the aforementioned jut. In this paper, we use an empirically chosen variable, namely. the time-rate of change of vehicle speed estimated from the point where ABS engaged to the point where measurement taken Experimental results shoe that the proposed method is effective to infer various control variables critical for the control of ABS.

• International Journal of CAD/CAM
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• 제9권1호
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• pp.17-24
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• 2010

For several years, researchers have focused on improving the integration of the CAD, CAM and Analysis through a better communication between the various analysis tools. This tendency to integrate the CAD/Analysis and automation of the corresponding processes requires data sharing between the various tasks using an integrated product model. We are interested in this research orientation to CAD/CAM/Analysis integration by rebuilding the CAD model (BREP), starting from the Analysis results (deformed mesh). Because this problem is complex, it requires to be split into several complementary parts. This paper presents an original interoperability process between the CAD and CAE. This approach is based on a new technique of rebuilding the CAD surface model (Nurbs, Bezier, etc.) starting from triangulation (meshed surface) as a main step of the BREP solid model. In our work, the advantages of this approach are identified using a centrifugal pump example.

• International Journal of Control, Automation, and Systems
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• 제6권2호
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• pp.223-233
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• 2008

A new output feedback controller design approach for flexible-joint (FJ) robots via the observer dynamic surface design technique is presented. The proposed approach only requires the feedback of position states. We first design an observer to estimate the link and actuator velocity information. Then, the link position tracking controller using the observer dynamic surface design procedure is developed. Therefore, the proposed controller can be simpler than the observer backstepping controller. From the Lyapunov stability analysis, it is shown that all signals in a closed-loop system are uniformly ultimately bounded. Finally, the simulation results of a three-link FJ robot are presented to validate the good position tracking performance of the proposed control system.