공기 스테이지의 형상 오차가 운동정밀도에 미치는 영향

류대원(Daewon Ryu),이재혁(Jae Hyeok Lee),박상신(Sang-Shin Park),김규하(Gyu Ha Kim) 한국트라이볼로지학회 2020 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.36 No.2

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.

성형 오차 예측 모델을 이용한 가변 성형 공정에서의 탄성 회복 보정

서영호(Y. H. Seo),강범수(B. S. Kang),김정(J. Kim) 한국소성·가공학회 2012 소성가공 : 한국소성가공학회지 Vol.21 No.8

The objective of this study is to compensate the elastic recovery in the flexible forming process using the predictive models. The target shape was limited to two-dimensional shape having only one curvature radius in the longitudinaldirection. In order to predict the shape error the regression and neural network models were established based on the finite element (FE) simulations. A series of simulations were conducted considering input variables such as the elastic pad thickness, the thickness of plate, and the objective curvature radius. Then, at sampling points in the longitudinal-direction, the shape errors between formed and objective shapes could be calculated from the FE simulations as an output variable. These shape errors were expressed to a representative error value by the root mean square error (RMSE). To obtain the correct objective shape the die shape was adjusted by the closed-loop using the neural network model since the neural network model shows a higher capability of estimating the shape error than the regression model. Finally the experimental result shows that the formed shape almost agreed with the objective shape.

청구야담 한문본 필사 오류 연구 : 음사(音寫)의 개입을 중심으로

이강옥(Lee Kang ok) 한국문학회 2014 韓國文學論叢 Vol.68 No.-

This paper studies cases of errors incurred in the process of transcribing Chunggu Yadam in Chino-Korean and analyzes the reasons of their errors. Four prominent reasons can be traced: the first type of errors occurring from homonyms; the second from words with similar shapes but different letters; the third from words with similar meanings but different sounds and shapes; the last from the different location of Chino-Korean letters. This paper limits its analysis only to the first cases. First, this paper illuminates the principles of phonetic transcription of Chunggu Yadam and then proceeds to analyze four types of errors resulting from the phonetic transcription process. 1) The first cases occurred when the transcriber used letters with different meanings even though he read and remembered the original texts correctly. 2) The second cases happened when the transcriber replaced the original words with the letters with same meanings that he thought were more suitable to the context. 3) The third cases resulted from incorrect transcription due to misreadings or false memories of the original words. The last cases were results of transcribing similar letters based on mistaken readings and rememberances of similar letters. Based on these observations, this paper explores the possibilities of utilizing these errors in phonetic transcription for comparative analysis of different editions of Chunggu Yadam. A Principle can be deduced that an edition presumed to be a later version has more phonetic transcription errors. An edition with phonetic transcription errors has little chance of being an earlier version than that without errors. Chino-Korean version of Chunggu Yadam contains fair numbers of transcription errors due to similar shapes of letters. Further analysis of these errors is necessary for a comprehensive study of transcription errors of Chino-Korean Chunggu Yadam. 본고는『청구야담』 한문본의 필사 과정에서 나타난 오류 사례를 적출하고 그에 대한 설명을 시도하였다. 여기에 해당하는 사례로는 1)한자의 음이 같고 글자가 다른 경우 2)한자의 모양이 비슷하지만 글자가 다른 경우 3)한자의 음과 모양이 전혀 다르지만 뜻이 비슷한 경우 4)한자의 위치가 다른 경우 등이 있는데 이 논문에서는 1)에 해당하는 경우만을 우선 다루었다. 먼저『청구야담』 필사 과정의 음사(音寫) 원리를 재구성하였다. 다음으로『청구야담』 필사 과정에 개입한 음사(音寫)의 양상과 필사 오류를 넷으로 나누어 분석하였다. 1)한자음을 정확하게 읽고 기억했지만 뜻이 다른 글자로 필사한 경우 2)한자음을 정확하게 읽고 기억하여 문맥이 통하는 다른 글자로 필사한 경우 3) 한자음을 부정확하게 읽었거나 정확하게 읽었지만 잘못 기억하여 글자를 정확하게 필사하지 못한 경우 4) 한자음을 비슷하게 읽었거나 기억하고 뜻이 비슷한 글자로 필사한 경우로 나누어 분석하였다. 이런 분석의 결과를 바탕으로 하여 『청구야담』 이본 비교에서의 음사 오류 현상 활용 가능성을 타진하였다. 먼저 음사 오류 현상에 대한 분석의 결과를 통하여, 『청구야담』 이본 중 최선본이라 할 과 그 다음 많은 단편을 싣고 있는 , 그리고 6책본을 대표하는 사이의 관계를 새롭게 따질 수 있었다. 그 결과 은 보다는 과의 상친성이 더 클 수도 있다는 결론을 도출하였다. 음사 오류 현상을 이본 간 선후 관계를 해명하는 데도 적극 활용할 방안을 도출하였다. 국어 음운 변천에서 ‘ㅚ’와 ‘ㅗ’의 교체 현상, 이중 모음의 단모음화 현상을 참조하여 이본 간 선후 관계를 밝힐 수 있었다. 후대본으로 짐작되는 이본일수록 음사 표기의 오류가 더 많이 난다는 원칙을 세울 수 있었다. 음사의 오류가 있는 이본은 그렇지 않는 이본보다 앞설 수 없을 가능성이 매우 크다고 보았다. 그런 방법론과 원칙으로써 이 보다 앞선 이본임을 밝힐 수 있었다.『청구야담』 한문본에는 한자의 비슷한 모양을 두고 일어난 필사 오류도 음사 오류 못지않게 많다. 또 부수(部首)의 오류는 소리와 모양이 함께 개입하여 생긴 필사 오류이다. 앞으로 이 두 국면에 대한 분석을 이어가서『청구야담』 한문본 필사 오류의 문제를 종합적으로 해명하고자 한다.

Shape error prediction and compensation of three-dimensional surface in flexibly-reconfigurable roll forming

Pan Liu,구태완,강범수 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.10

The Flexibly-reconfigurable roll forming (FRRF) scheme as one of the advanced continuous roll forming processes consists of upperand lower flexible rollers that can be controlled by each reconfigurable punch module. The shape error in the FRRF process often resultsin undesirable changes in the shape of the deformed surface and brings about a deviation in the precision of the deformed product. Thisstudy considers the changes in the shape error of a deformed configuration by controlling the non-uniform gap between both flexiblerollers in the transverse direction. A Non-uniform rational B-spline (NURBS) type control methodology is introduced based on the transversetarget curve and the thickness reduction ratio. The function for the transverse target curve is reconstructed by using a NURBS curve,and the function of the reduction ratios of the thickness is assumed to have linear increments. Finite element simulations are conductedfor the FRRF process with the AA5052-H32 sheet material by applying NURBS-type control methodology for both flexible rollers. Thetransverse shape error of the three-dimensional surface is predicted by using a numerical approach, and its results are experimentallyverified. A Reverse displacement compensation (RDC) method is adopted to compensate the transverse shape error of the deformedsurface. Consequently, the proposed RDC method is validated as a suitable approach to address the transverse shape error. This methodcontributes to further developing capabilities to modify the profiles of the upper and lower flexible rollers in the flexibly-reconfigurableroll forming process for various 3D surface parts.

STL 포맷의 급속곡면 오류 수정을 위한 시스템 개발

손영지,김순경 동의공업대학 1998 論文集 Vol.24 No.1

This paper recommends database construction for STL data and a new method of Delaunay's triangulation in order to decrease volume errors by verifying STL file errors and modifying hole errors. Each vertex for the boundary coordinates of the verified hole errors was analyzed according to the following cases: planes or slow curves, edges, apexes, and rapid curves, In each case, a different modification process was adopted. With this method, most errors resulting from the conversion into STL data. as well as many volume errors arising from error modification, were decreased.

음각 점진성형에서 치수정밀도에 영향을 미치는 형상 파라미터 분석

강재관(Jae Gwan Kang),강한수(Han Soo Kang),정종윤(Jong-Yun Jung) 한국산업경영시스템학회 2016 한국산업경영시스템학회지 Vol.39 No.4

Incremental sheet forming (ISF) is a highly versatile and flexible process for rapid manufacturing of complex sheet metal parts. Compared to conventional sheet forming processes, ISF is of a clear advantage in manufacturing small batch or customized parts. ISF needs die-less machine alone, while conventional sheet forming requires highly expensive facilities like dies, molds, and presses. This equipment takes long time to get preparation for manufacturing. However, ISF does not need the full facilities nor much cost and time. Because of the facts, ISF is continuously being used for small batch or prototyping manufacturing in current industries. However, spring-back induced in the process of incremental forming becomes a critical drawback on precision manufacturing. Since sheet metal, being a raw material for ISF, has property to resilience, spring-back would come in the case. It is the research objective to investigate how geometrical shaping parameters make effect on shape dimensional errors. In order to analyze the spring-back occurred in the process, this study experimented on Al 1015 material in the ISF. The statistical tool employed experimental design with factors. The table of orthogonal arrays of L 8 (2 7 ) are used to design the experiments and ANOVA method are employed to statistically analyze the collected data. The results of the analysis from this study shows that the type of shape and the slope of bottom are the significant, whereas the shape size, the shape height, and the side angle are not significant factors on dimensional errors. More error incurred on the pyramid than on the circular type in the experiments. The sloped bottom showed higher errors than the flat one. 1)

Accuracy Enhancement of Parameter Estimation and Sensorless Algorithms Based on Current Shaping

Jin-Woong Kim,Jung-Ik Ha 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.

가변단면 롤 성형공정의 형상변형 방지를 위한 공정변수의 해석적 분석에 관한 연구

박종철(J. C. Park),차명환(M. H. Cha),김돈건(D. G. Kim),양동열(D. Y. Yang) 한국소성가공학회 2013 한국소성가공학회 학술대회 논문집 Vol.2013 No.5

Flexible roll forming process is the process to fabricate beams with variable cross-sections for industrial applications. The beams fabricated by flexible roll forming have shape errors. It is necessary to prevent the shape error to apply the beams to industrial fields. In this study, as the preliminary investigations, the processing parameters of the flexible roll forming and the additional processes to prevent the shape errors, the constant blank holders, the flexible blank holders, are investigated. The shape errors of each process are compared. In case of the beams fabricated by the flexible roll forming and the flexible blank holders, the shape errors are prevented firstly.

Accuracy Enhancement of Parameter Estimation and Sensorless Algorithms Based on Current Shaping

Kim, Jin-Woong,Ha, Jung-Ik The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.

Accuracy Enhancement of Parameter Estimation and Sensorless Algorithms Based on Current Shaping

김진웅,하정익 전력전자학회 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.