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선박 엔진 크랭크샤프트 가공용 다기능 5축 복합가공기의 구조설계
최영휴,김실근,장성현,조용주,하종식 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
This paper describes a case study on structural design of a 5-axes multi-tasking machine tool for machining marine engine crankshaft. We carried out static and dynamic structural analysis for several design alternatives of the machine tool by using ANSYS. From the analysis results, we could decide a feasible design candidate. And then we carried out design optimization of the design candidate for light weight and minimum compliance using genetic algorithm. After the prototype machine tool was made, natural frequency and dynamic stiffness of the machine tool structure were obtained by using a experimental modal test and a random excitation test, respectively. The test results showed that the prototype machine tool has sufficient structural stiffness and high natural frequency.
Linear Motor 이송계의 진동 최소화를 위한 이송속도 최적화
최영휴,홍진현,최응영,김태형,최원선 한국공작기계학회 2004 한국공작기계학회 추계학술대회논문집 Vol.2004 No.-
Linear motor feed drive systems have been broadly used in machine tools or precision automatic feed systems. Recently, modern machine tools require high speed and high precision feed drive system to achieve high productivity. Unfortunately, a feed drive system, even though it was optimum designed, may experience severe transient vibrations during high-speed operation if its feed rate control is unsuitable. A rough feed rate curve having discontinuity in its acceleration profile causes a serious vibration problem in the feed slides system. This paper presents a feed rate optimization of a machine tool feed slide system, which is driven by a linear motor, for its minimum vibrations. Firstly, a 4-degree-of-freedom lumped parameter model is proposed for the vibration analysis of a linear motor driven machine tool feed drive system. Next, a feed rate optimization of the feed slide is carried out for minimum vibrations. The feed rate curve optimization strategy is to find out the most appropriate acceleration profile with jerk continuity. Of course, the optimized feed rate should approximate to the desired one as possible. A genetic algorithm with variable penalty function was used in this feed rate optimization.
3차원 DOUBLE-TRACK 차량모델을 이용한 자동차의 주행거동해석
최영휴 國立 昌原大學校 産業技術硏究所 1994 産技硏論文集 Vol.8 No.-
The conventional 2-dimensional single track vehicle model has degrees of freedom related to only planar motions, and neglects the effects of suspension systems on vehicle manoeuvres. Whereas a 3-dimensional 12-degree-of-freedom vehicle model was proposed, in this study, to analyze handing and riding behaviors with taking into account the effects of nonlinear suspension and steering systems. The computed results of the proposed model are in good agreement with test results compared to the 2-dimensional model. Especially the proposed model showed the better accuracy near the characteristic speed and in high lateral accelerated manoeuvres.
평면운동모델을 이용한 LMG 상에서 이송되는 Cross Head의 사행동 해석
최영휴,김성훈,정택수 國立 昌原大學校 産業技術硏究所 2002 産技硏論文集 Vol.16 No.-
In this paper, a simple 2 D.O.F. planar motion model is proposed in order to analyze the snake motion of a cross head assembly travelling on linear huide rails. In the proposed mathematical model, the head assembly and a ball screw are assumed to be rigid, but the rear-panel of the machining center is assumed to be flexible. The equations of motion of the proposed model are derived and solved by Runge-Kutta method to determine vibration responses of the head assembly due to some applied traction forces.
다기능 5축 복합가공기 구조물의 저진동, 고강성 구조 최적설계
최영휴,김성민,장성현,황현영,정용민 한국공작기계학회 2007 한국공작기계학회 추계학술대회논문집 Vol.2007 No.-
This paper presents structural design optimization of a 5-axes multi-tasking machine for light weight and minimum compliance using genetic algorithm based 2-step optimization method. The design problem, in this study, is to determine thickness of structural members which minimize the static compliance, dynamic compliance and weight of the machine structure simultaneously under several constraints such as dimensional design constraints. Optimization results showed apparent reduction in static and dynamic compliances at the spindle nose of the machine in spite of reduction in machine weight.
최영휴 國立 昌原大學校 産業技術硏究所 1994 産技硏論文集 Vol.8 No.-
A quarter car model was employed to analyze vibration control effects on the carbody and wheel hop according to these two kinds of control methods which are 'modal damping control' and 'modal skyhook control' based on modal analysis. The validity of the proposed control methods was shown through the comparison of their control effects with those from LQG and LQR control methods. The proposed methods are more simple, effective, and energy-saving than the others because proposed methods use only relative or absolute velocity feedback with rather low gains, while LQG and LQR methods use full state feedback of carbody acceleration, relative velocity, absolute velocity, and tire deflection with comparatively high feed-back gains.
가변 벌점함수 유전알고리즘을 이용한 금형가공센터 고속이송체 구조물의 최적설계
최영휴,차상민,김태형,박보선,최원선 한국공작기계학회 2003 한국공작기계학회 춘계학술대회논문집 Vol.2003 No.-
In this paper, a multi-step optimization using a G.A.(Genetic Algorithm) with variable penalty function is introduced to the structural design optimization of a high speed machining center. The design problem, in this case, is to find out the best cross-section shapes and dimensions of structural members which minimize the static compliance, the dynamic compliance, and the weight of the machine structure simultaneously. The first step is the cross-section shape optimization, in which only the section members are selected to survive whose cross-section area have above a critical value. The second step is a static design optimization, in which the static compliance and the weight of the machine structure are minimized under some dimensional constraints and deflection limits. The third step is a dynamic design optimization, where the dynamic compliance and the structure weight are minimized under the same constraints as those of the second step. The proposed design optimization method was successful applied to the machining center structural design optimization. As a result, static and dynamic compliances were reduced to 16% and 53% respectively from the initial design, while the weight of the structure are also reduced slightly.
암호화 기법을 이용한 재구성 가능형 마이크로 공작기계의 구조형태 창성 방법에 관한 연구
최영휴,장성현,김성민,김인수,박종권 한국공작기계학회 2006 한국공작기계학회 추계학술대회논문집 Vol.2006 No.-
This study presents a new method to generate machine structural configurations of MRmMT (Modular-Reconfigurable micro Machine Tool) systematically in the embodiment design step. The two core approaches to create machine tool structural configurations, in our proposed design method, are cryptographic mapping and machining function proving. Cryptographic mapping approach includes; 1) encoding all the structure modules into binary codes and then storing the graphics and digital codes in the module library, 2) cryptographic operating to create possible combined configurations from any two or several modules by using vector quadratic form expansion of the encoded binary codes, 3) to obtain the resulting structural configurations by decoding the operated binary codes using the module library. Machining function proving is to check up machining ability of a created machine tool configuration. Machining function proving is basically achieved by scalar product of the direction vectors of spindle (or tool) and table (or work piece) modules. Our method was well applied and succeeded in creating feasible machine configurations for a 3-axes reconfigurable micro milling machine from 7 modules spindle, table, bed, column, and 3-translational slide modules.