• 한국정밀공학회지
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• 제15권8호
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• pp.145-155
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• 1998

An $H{\infty}$ controller with a roll eccentricity filter is proposed to alleviate the effect of entry thickness variation and roll eccentricity occured in rolling stands themselves of tandem cold mills. A robust controller to the disturbances is designed by H$_{\infty}$ control techniques, which can reflect the input direction of disturbances and the knowledge of disturbance spectrum in the frequency domain. First, fundamental problems in tandem cold mills such as process transport delay inherent in the exit thickness measurement and the feedforward loading of roll eccentricity signals on the exit thickness be overcome by the roll eccentricity filtering and the compensation for the error of gaugemeter thickness estimator. And non-satndard $H{\infty}$ control problem caused by the selection of weighting function having poles on the $J{\omega}$-axis is discussed. The resultant controller composed by an $H{\infty}$ controller and an estimator for the roll eccentricity is evaluated through computer simulations. The effectiveness of the proposed control method is compared to that of the conventional LQ controller method and a feedforward controller for the roll eccentricity, which has been already studied.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.300-306
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• 2005

This paper presents the methodology for measuring eccentricity of the machined cylindrical part using CCS(cylindrical capacitance spindle sensor) signal in the CNC turning process. We use capacitance type sensor to take full advantage of averaging effect by using large capacitance area to encompass the whole side of a sensor. The intentionally proposed initial eccentricity is applied to the experimental testpieces, and their resultant relationships between CCS orbits and eccentricities are investigated. As a result, the possibility as a automatic detection apparatus for the CNC lathe is considered based on the linearities of CCS signal and magnitude of eccentricity of machined cylindrical surfaces.

• Tribology and Lubricants
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• 제36권2호
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• pp.68-74
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• 2020

In this study, the effect of the shape error of a guideway on the movement of a stage that uses an air bearing is analyzed. The shape error of moving parts supported by the air bearing is known not to affect the vibrations of moving parts as much as the magnitude of the shape error. This is called the "averaging effect." In this study, the effect of shape error on a guideway, as well as the averaging effect of an air-bearing system, is analyzed theoretically using a dynamic-analysis program. The dynamic-analysis program applies a commercially available code in COMSOL and solves the Reynolds equation between the stage and the guideway, along with the equation of motion of the stage. The stage is modeled as a two-degree-of-freedom system. The shape error is applied to the film thickness function in the form of a sine wave. The stage movement is analyzed using the fast Fourier transform process. The eccentricity and tilting are found to be proportional to the amplitude of the shape error of the guideway. Stage vibrations are less than 10% of the amplitude of the shape error on the guideway. This means that the averaging effect of the air bearing is verified quantitatively. Moreover, if the air supply position matches the shape error in the guideway, there is a notable change in eccentricity and tilting.

• 대한기계학회논문집A
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• 제23권7호
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• pp.1238-1244
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• 1999

Using a cylindrical worm gear under the actual condition of static loading, tooth fillet strains and transmission errors have been measured. The maximum strain occurs on the filet region of the center of the 1st mating tooth. Tooth fillet strain changes most sensitively according to the variations of the center distance and recess side eccentricity than the access side eccentricity. Even the no-backlash worm gear shows the transmission errors.

• 한국암반공학회:학술대회논문집
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• 한국암반공학회 2000년도 암반공학문제의 수치해석(Numerical Analysis in Rock Engineering Problems)
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• pp.63-66
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• 2000

링 시험펀의 크기와 편심에 따른 응력변화를 FLAC으로 분석하였다. 분석 결과 중공의 크기가 일정한 범위에서만 안정된 값을 얻을 수 있었다. 중공의 크기 오차를 줄이기 위한 상대 공반경은 약 0.3이 적절할 것으로 평가되었다. 한편 중공의 관심 오차가 커지면 응력분포가 불균일하게 되어 정확한 인장강도 산정이 어려운 것으로 사료되었다. 적절한 인장강도를 얻기 위해 중공의 편차는 일정한 정도로 한정하여야 할 것으로 생각된다. 편심으로 인한 오차를 10% 이내로 제한하기 위해서는 중공의 중심은 가압방향에 수평한 방향으로 3%, 수직한 방향으로는 10% 이내가 되어야 하는 것으로 분석되었다.

• 터널과지하공간
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• 제10권3호
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• pp.316-319
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• 2000

링 시험편의 크기와 편심에 따른 응력변화를 FLAC으로 분석하였다. 분석 결과 중공의 크기가 일정한 범위에서만 안정된 값을 얻을 수 있었다. 중공의 크기 오차를 줄이기 위한 상대 공반경은 약 0.3이 적절할 것으로 평가되었다. 한편 중공의 편심 오차가 커지면 응력분포가 불균일하게 되어 정확한 인장강도 산정이 어려운 것으로 사료되었다. 적절한 인장강도를 얻기 위해 중공의 편차는 일정한 정도로 한정하여야 할 것으로 생각된다. 편심으로 인한 오차를 10% 이내로 제한하기 위해서는 중공의 중심은 가압방향에 수평한 방향으로 3%, 수직한 방향으로는 10% 이내가 되어야 하는 것으로 분석되었다.

• 대한기계학회논문집A
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• 제36권2호
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• pp.195-201
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• 2012

다양한 소비자의 요구에 따라 가공된 제품을 좀더 신속하고 정확하게 측정할 수 있는 공작기계 내 자동계측장치를 적용하는 사례가 급격히 증가하고 있다. 자동 계측으로 가장 많이 활용되는 접촉식 측정 프로브는 주로 공작물의 가공 원점을 설정하고, 정확한 치수 검사를 통한 불량유무 판정 및 보상가공에 많이 활용된다. 따라서 본 연구에서는 기기상 자동계측장치인 접촉식 측정 프로브를 활용하여 가공된 형상을 신속하고 정확하게 측정하는 방법을 연구하였으며 이를 위하여 가장 많이 활용되는 홀 측정 사이클에 대한 매크로 프로그램을 개발하였다. 또한 측정 시 홀의 진원도 오차에 따라 발생할 수 있는 편심량을 시뮬레이션하여 분석하였으며 본 연구의 신뢰성을 높이기 위하여 기기상에서 개발된 홀 측정 매크로 프로그램을 이용하여 홀플레이트에 대한 측정이 이루어졌으며, 진원도 오차에 따른 편심량을 검증하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2004년도 추계학술대회 논문집
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• pp.604-608
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• 2004

In this paper, an efficient method is proposed to analyze the radial error of a miniaturized-high speed spindle system. Initially, a device is constructed for measuring the radial error motion using capacitance sensors. The capacitance sensors are placed perpendicular to the axis of the shaft and at 90o to each other. The spindle is rotated at high speed and the profile of the spindle is recorded. An algorithm is developed for analyzing the spindle data and determining the radial error of spindle. The present algorithm uses homogeneous transform matrix (HTM) method and iterative process for determining the radial error. The analysis procedure is performed for different speeds of the spindle. The data obtained from the present system and the results of evaluation are also presented in this paper. It is observed that this method is effective in determining and analyzing the spindle errors for high speed miniaturized spindle.

• 제어로봇시스템학회논문지
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• 제12권10호
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• pp.962-967
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• 2006

Indoor positioning is highlighted recently, and various kinds of indoor positioning systems are under developments. Since positioning systems have their own characteristics, proper positioning scheme should be chosen according to the required specifications. Positioning methods are classified into time-based and angle-based one. This paper presents the error analysis of time-based and angle-based location methods. Because measurements of these methods are nonlinear, linearizations are needed in both cases to estimate the user position. In the linearization, Gauss-Newton method is used in both cases. To analyze the position error, we investigate the error ellipse parameters that include eccentricity, rotation angle, and the size of ellipse. Simulation results show that the major axes of TOA and AOA method lie in different quadrants at most region of workspace, especially where the geometry is poor. When the TOA/AOA hybrid is employed, it is found that the error ellipse is reduced to the intersection of ellipses of TOA and AOA.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.963-968
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• 2003

The continuous process systems usually consists of various components: driven rollers. idle rolls, load-cell and so on. Even a simple fault in a single component in the line may cause a catastrophic damage on the final products. Therefore it is absolutely necessary to diagnosis the components of the continuous systems. In this paper, an adaptive eccentricity compensation method is presented. And a new diagnosis method for transverse roll shape defects on rolling process is developed. The new method was induced from analyzing the rolling mechanism by using rolling force model, tension model, Hitchcock's equation, and measured delivery thickness of materials etc. Computer simulation results also show that the proposed diagnosis methods is very effective in the diagnosis of 3-D roll shape