• 대한토목학회논문집
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• 제44권5호
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• pp.707-717
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• 2024

최근 산업현장에서 발생하는 안전사고를 줄이기 위한 해결책으로 무인화 및 자동화 기술 도입이 적극적으로 고려되고 있다. 그러나 교량 시공 현장은 날씨와 지형과 같은 현장의 복잡성과 작업이 반복적이거나 표준화되기 어렵다는 점 때문에 다른 산업에 비해 관련 연구개발이 어려운 영역으로 인식되고 있다. 본 논문에서는 철근 조립, 콘크리트 타설, 고소에서의 거푸집 해체 및 조립과 같은 작업으로 인해 고위험 작업 환경으로 여겨지는 교각 시공에 있어 무인 및 자동화 시공을 위한 거푸집 시스템을 개발하였다. 이를 위해, 거푸집은 수동으로 이루어지던 해체 및 조립 과정을 대체할 수 있도록 전동 스핀들과 자동 승하강 시스템을 적용하였다. 또한, 상부 작업대에는 철근 조립 및 콘크리트 타설 작업을 대체할 수 있는 매니퓰레이터를 도입하였다. 제안된 기술의 검증을 위해, 가조립 테스트를 통해 교각 무인 시공을 위한 자동화 거푸집 시스템의 가능성을 입증하고자 하였다.

• 한국산학기술학회논문지
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• 제16권4호
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• pp.2350-2355
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• 2015

본 연구에서는 축과 베어링으로 구성된 공작기계 주축 설계를 위한 1차원 유한요소 해석을 자동화하기 위한 툴을 개발하였습니다. 객체지향 프로그래밍을 기반으로 하기 때문에, CAD 시스템의 객체를 사용할 수 있습니다. 스핀들 시스템을 정의하기 위한 축의 단면과 베어링 강성과 같은 최소한의 데이터를 입력할 필요가 있으며, 그 데이터를 기반으로 형상 모델을 먼저 만들고, 그리고, 1차원 빔과 스프링 요소로 구성된 유한요소 모델로 변환합니다. 본 툴을 위해서 개발된 사용자 인터페이스는 사용자가 툴과 상호교류할 수 있도록 도와줍니다. 본 툴은 다수의 설계 변경과 그 후에 수행되는 유한요소해석 과정을 자동화함으로써 최소한의 시간과 노력으로 공작기계 주축 시스템의 근사 최적 설계를 발견할 수 있도록 해줍니다.

• 한국산업정보학회논문지
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• 제12권5호
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• pp.110-119
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• 2007

최근 기업의 사업영역이 확대됨에 따라 다양한 이해관계자들과의 거래 및 협력관계가 이루어지고 있다. 이해관계자와의 효율적인 업무 프로세스 관리와 기업의 목표를 효과적으로 달성하기 위해 정보기술을 적극적으로 활용하고 있지만, 보안 등 정보기술의 위험성 또한 증가하고 있다. 이러한 시장 환경에 따라 IT 거버넌스 산업이 급속하게 성장하고 있으며, IT 거버넌스 솔루션을 제공하는 업체간의 경쟁 또한 심화되고 있다. 특히 IT를 기반으로 한 벤처기업의 시장진입이 이루어지고 있지만, 브랜드 관리를 포함한 마케팅 능력의 부재로 어려움을 겪고 있다. 본 연구는 스핀오프 벤처기업의 브랜드 명과 포지셔닝을 IT 거버넌스 솔루션을 개발한 기업의 사례를 중심으로 고찰해 보았다. 연구결과를 하면 첫째, IT 벤처기업은 브랜드이미지를 구축하는데 기업의 역량을 집중시킬 필요성이 있다는 것이다. 소비자에게 호감가고 독특하며 강한 브랜드 이미지를 구축해 놓으면 경쟁 제품의 공격으로 인한 범용품화의 위험을 극복할 수 있다. 둘째, 브랜드를 통해 소비자에게 제품의 기능적인 가치 이상을 창출하고 이를 전달해 나갈 수 있어야 한다. 즉 하이테크 기업도 소비자의 기능적 욕구에만 머물지 말고 고객의 감성적, 상징적인 욕구를 충족시켜 주는 것에도 관심을 가질 필요가 있다.

• 대한기계학회논문집A
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• 제22권1호
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• pp.33-43
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• 1998

High cutting speeds and feeds are essential requirements of a machine tool structure to accomplish its basic function which is to produce a workpiece of the required geometric form with an acceptable surface finish at as high a rate of production as is economically possible. Since the bearings in high speed spindle units are the main heat source of the total cutting system, in this work, the thermal characteristics of the spindle bearing system with a tilting axis were investigated using finite element methods to improve the performance of the spindle bearing system. Based on the theoretical results, a specially designed prototype spindle bearing system has been manufactured. Using the manufactured spindle bearing system, the thermal characteristics were measured. From the comparison of the experimental results with the theoretical ones, it was found that the finite element method predicted well the thermal characteristics of the spindle bearing system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.407-413
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• 2008

This paper investigates the dynamics of a HDD spindle system due to the change of FDBs. Flying height of the HDD spindle system is determined through the static analysis of the FDBs, and the stiffness and damping coefficients are calculated through the dynamic analysis of the FDBs. Free vibration characteristics and shock response of the HDD spindle system are analyzed by using the finite element method and the mode superposition method. Experimental modal test is also performed to verify the accuracy of the proposed method. This research shows that the stiffness coefficients of journal heating mostly affect the rocking frequencies because their magnitude are within the range of the stiffness of supporting structure. It also shows that the damping coefficients of thrust bearing mostly affect the axial frequency because the stiffness of thrust bearing is much smaller that that of supporting structure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.840-846
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• 2007

This paper investigates the dynamic behavior of a HDD spindle system due to the imperfect roundness of a rotating shaft. The shaft of a spindle motor rotates with eccentricity by the unbalanced mass of the rotating part. The eccentricity generates the run-out of a spindle motor which results in the eccentric motion of a rotating part. Roundness of a shaft affects this motion which limits the memory capacity of a HDD. This research proposes a modified Reynolds equation for the coupled journal and thrust FDBs to include the variable film thickness due to the roundness. Finite element method is used to solve the Reynolds equation for the pressure distribution. Reaction forces and friction torque are obtained by integrating the pressure and shear stress, respectively. The dynamic behavior is determined by solving the equations of a motion of a HDD spindle system in six degrees of freedom with the Runge-Kutta method to characterize the motion of a rotating part. This research shows that the roundness of a rotating shaft causes the excitation frequency with integer multiple of a rotating frequency.

• Tribology and Lubricants
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• 제15권3호
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• pp.257-264
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• 1999

Recently as electronics and semi-conductor industry develop, ultra-precision machine tools that use air-spindle with externally pressurized air bearing appear in need of ultra-precision products which demand high precision property. Effects of air compressibility absorbs the vibration of shaft, this is called averaging effect, however, the higher running accuracy is demanded by degrees, the more important factor is machining errors that affect running accuracy of shaft. Actually, it would be very important in the view points of running accuracy to understand effects of machining errors on the running accuracy of the spindle system quantitatively to design and manufacture precision spindle system in the aspect that efficiency in manufacturing spindle system and performance in operation. So fu, there are some researches on the effects that machining error affect running accuracy. However, because these researches deal with one bearing of spindle system, these results aren't enough to explain how much machining errors affect running accuracy in the typical spindle system overall. In this study, we investigate the effects of the perpendicularity error of bearing and shaft on running accuracy of spindle system that consists of journal and thrust bearing theoretically, and suggest design guideline about shape tolerances.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.128-135
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• 2006

This paper presents a finite element method to analyze the free vibration of a flexible HDD composed of the spinning disk-spindle system with fluid dynamic bearings(FDBs), the head-suspension-actuator with pivot bearings, and the base plate with complicated geometry. Experimental modal testing shows that the proposed method well predicts tue vibration characteristics of a HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head-suspension-actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of a HDD and to design a robust HDD against shock.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권5호
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• pp.253-259
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• 2005

Magnetic encoder with relatively low pulse per rotation is generally used for detecting speed of the high-speed rotating machine. It is due to the fact of the mechanical problems of vibration and bearing stiffness and also the limit of maximum output pulse of the mounted encoder. The magnetic encoder is divided into two types, that is, toothed gear-wheel method and magnetic wheel method according to the shape of the rotation disk. In case of detecting speed by the tooth gear-wheel, the encoder itself can be acted as the additional inertia where the number of tooth determining the output pulse and the width of the wheel detecting the change of the magnetic flux density are relatively enough large considering the volume of the rotating machine. While the magnetic wheel method has the limit of the magnetizing number of the ring magnet, there is relatively few, if nv, the influence of inertia on the machine. In this paper, it is proposed a simple magnetic wheel encoder suited for the high speed rotating machine and the method of signal processing and the output characteristics are examined through the V/F operation of max 48,000(rpm) and 2.4(KW) spindle motor.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.852-858
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• 2007

This paper investigates the dynamic characteristics of a tilted HDD spindle system with fluid dynamic bearings (FDBs). Tilting motion of a HDD spindle system may be caused by improper manufacturing tolerance, such as imperfect cylindricity between shaft and sleeve of FDBs, imperfect perpendicularity between shaft and thrust as well as the gyroscopic moment of the unbalanced mass of the rotating part. Tilting motion may result in the instability of the HDD spindle system and it may increase the disk run-out to limit memory capacity. This research proposes a modified Reynolds equation for the coupled journal and thrust FDBs to include the variable film thickness due to the cylindricity and the perpendicularity. Finite element method is used to solve the Reynolds equation for the pressure distribution. Reaction forces and friction torque are obtained by integrating the pressure and shear stress, respectively. The dynamic behavior is determined by solving the equations of a motion of a HDD spindle system in six degrees of freedom with the Runge-Kutta method to study whirling and tilting motions. This research shows that the cylindricity and the perpendicularity increase the tilting angle and whirl radius of the rotor.