• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1028-1032
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• 2004

In order to prevent machine tool feed slide system from transient vibrations during operations, machine tool designers usually adopt some typical design solutions; box-in-box typed feed slides, optimizing moving body for minimum weight and dynamic compliance, and so on. Despite all efforts for optimizing design, a feed drive system 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 ball screw driven machine tool feed slide system for its minimum vibration. Firstly, a ball screw feed drive system was mathematically modeled as a 6-degree-of-freedom lumped parameter system. Next, a feed rate optimization of the system was carried out for minimum vibrations. The main idea of the feed rate optimization is to find out the most appropriate smooth acceleration profile with jerk continuity. A genetic algorithm was used in this feed rate optimization

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.321-325
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• 2004

Linear motor feed drive systems have been broadly used in machine tools or precision automatic feed systems. Recently, modem 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.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.962-966
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• 2004

Ball screw 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 and 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 slide system. This paper presents a feed rate optimization of a machine tool feed slide system, which is driven by a ball screw, for its minimum vibrations. Firstly, a 6-degree-of-freedom lumped parameter model was proposed for the vibration analysis of a ball screw driven machine tool feed drive system. Next, a feed rate optimization of the feed slide was carried out for minimum vibrations. The feed rate curve optimization strategy is to find out the most appropriate acceleration profile having finite jerk. 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.

• 한국전산구조공학회논문집
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• 제26권4호
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• pp.223-231
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• 2013

본 논문에서는 물성이 균일하지 않은 반무한 고체영역의 탄성파속도 분포를 재구성하기 위한 시간영역 Gauss-Newton 전체파형 역해석 기법을 소개한다. 반무한 영역을 유한 계산영역으로 치환하기 위하여 유한영역의 경계에 수치적 파동흡수 경계조건인 perfectly-matched-layers(PMLs)를 도입하였다. 이 역해석 문제는 PML을 경계로 하는 영역에서의 탄성파동방정식을 구속조건으로 하는 최적화 문제로 성립되며, 표면에서 측정된 변위응답과 혼합유한요소법에 의해 계산된 응답간의 차이를 최소화함으로써 미지의 탄성파속도 분포를 결정한다. 이 과정에서 Gauss-Newton-Krylov 최적화 알고리즘과 정규화기법을 사용하여 탄성파속도의 분포를 반복적으로 업데이트하였다. 1차원 수치예제들을 통해 Gauss-Newton 역해석으로 부터 재구성된 탄성파속도의 분포가 목표값에 충분히 근사함을 보였으며, Fletcher Reeves 최적화 알고리즘을 사용한 기존의 역해석 결과에 비해 수렴율이 현저히 개선되고 계산 소요시간이 단축됨을 확인할 수 있었다.

• 한국산학기술학회논문지
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• 제17권8호
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• pp.344-351
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• 2016

열차 운영사의 관점에서, 열차 운행에 관한 주요 관심사는 정해진 운행시간의 준수뿐만 아니라, 그와 동시에 열차 운행을 위해 소비되는 에너지 량을 최소화하는 것이다. 일반적인 수동 운전시, 기관사는 운행 노선의 특성에 따라 미리 규정된 최대 속도 프로파일을 기준으로, 노치를 제어함에 따라 규정 속도를 넘지 않도록 열차의 가감속을 조절한다. 이때 규정 속도를 준수하면서 동시에, 전체 운행 중에 소요되는 에너지 량의 절감을 위해, 기관사가 적절한 노치를 선택할 수 있는 구간별 노치 지정 가이드가 있어야 하며, 이는 운행구간에서의 노치 단계 최적화라는 절차를 통해 가능하다. 본 논문에서는 일반적인 운행 환경뿐만 아니라, 열차가 운행 중에 일시적으로 잔여구간의 트랙 정보 또는 규정속도 정보가 변경되는 이벤트 발생시에도 변화된 정보들을 기반으로 실시간으로 잔역구간의 노치 단계를 최적화 할 수 있는 유전 알고리즘을 활용한 실시간 노치 최적화 방안을 제안하였다. 또한 유전 알고리즘을 통해 얻어진 최적해를 적용할 때 에너지 절감 효과와 최적해 수렴특성에 관하여 분석하였다.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.125-131
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• 1999

For linkage mechanisms driven by a cam, cam profile is the major design factor and is determined by the cam follower motion. If a cam mechanism has additional kinematic linkage besides cam and follower then the follower motion should be specified from the motion of end linkage member so that cam would be able to generate the desired end linkage motion. In this paper, a cam-linkage mechanism is constructed with the combinations of modular linkage elements including cam and follower and as a result, a planar cam-linkage mechanism design software with the cam profile optimization function is developed and presented.

• 소음진동
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• 제8권4호
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• pp.632-642
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• 1998

A method based on finite element discretization is developed for optimizing the polarization profile of PVDF film to create the modal transducer for specific modes. Using this concept, one can design the modal transducer in two-dimensional structure having arbitrary geometry and boundary conditions. As a practical means for implementing this polarization profile without repoling the PVDF film the polarization profile is approximated by optimizing electrode patterns, lamination angles, and poling directions of the multi-layered PVDF transducer. This corresponds to the approximation of a continuous function using discrete values. The electrode pattern of each PVDF layer is optimized by deciding the electrode of each finite element to be used or not. Genetic algorithm, suitable for discrete problems, is used as an optimization scheme. For the optimization of each layers lamination angle, the continuous lamination angle is encoded into discrete value using binary 5 bit string. For the experimental demonstration, a modal sensor for first and second modes of cantilevered composite plate is designed using two layers of PVDF films. The actuator is designed based on the criterion of minimizing the system energy in the control modes under a given initial condition. Experimental results show that the signals from residual modes are successfully reduced using the optimized multi-layered PVDF sensor. Using discrete LQG control law, the modal peaks of first and second modes are reduced in the amount of 12 dB and 4 dB, resepctively.

• 한국소음진동공학회논문집
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• 제26권5호
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• pp.546-551
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• 2016

The objective of this study is to investigate the response delays between piezo-stack actuator and the displacement magnifier of jetting dispenser and to reduce its falling time in terms of displacement optimization. The dispenser is driven by the dual piezo-stack actuators with a hinge lever mechanism to precisely control flow rate of the working fluid (3000 cP). It is commonly found that piezo actuator-driven jetting dispensers involving viscous working fluids have displacement optimization problem for ideal performance. The response delay of the system is caused by the phenomenon that the displacement magnifier cannot exactly follow the motion of the piezo actuators. The response delay may lower the performance of the system due to the inaccurate discharge of working fluid or even damages to the system itself due to inharmonious motion of piezo actuators with lever system. To reduce its response delay, a new displacement profile obtained from displacement optimization is suggested; its performance is tested through finite element analysis; and experiments are carried out to verify the performance of the obtained displacement profile.

• 설비공학논문집
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• 제18권2호
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• pp.95-102
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• 2006

This study analyzes and optimizes a design for a trapezoidal profile straight fin using one-dimensional analytical method. The heat transfer, fin length and fin height are optimized as a function of fin volume, fin shape factor and fin base length. In this optimization, convection characteristic number over fin surface and that of fluid inside fin wall are considered. One of the results shows that the maximum heat loss increases as fin volume increases and both fin shape factor and fin base length decrease.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.235-242
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• 2001

An optimization algoriam for the optimum design of prestressed concrete (PSC) box girder bridges is proposed in this paper. In order to optimize the tendon profile efficiently, a reduced basis technique is introduced. The optimization algorithm which includes the tendon profile, tendon size and concrete dimensions optimization problem of the PSC box girder bridges is verified on the Genetic algorikhm (GA) from the numerical examples. it may be positively stated that the optimum design of the PSC box girder bridges based on the new approach proposed in this study will lead to more rational and economical design compared with the currently available designs.