• 대한기계학회논문집
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• 제9권5호
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• pp.590-597
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• 1985

본 논문에서는 위치오차는 가공전 밀링베드를 수치제어 장치를 이용하여 가공 면에 수직한 방향으로 움직여 수치제어 장치인 스텝모우터의 분해능 한계 내에서 보정 하고 또한 공구휨에 상당하는 만큼 이 송속도를 더함으로써 제어하며, 파형오차는 이 송속도와 공구처짐 사이의 관계를 수정된 Taylor의 공구식으로 모형화하고 절삭공정중 이송속도를 적절히 조절하여 공구의 휨양을 제어함으로써 스텝모우터를 갖는 밀링머시 인에서 길이 508mm,두께 20mm의 두꺼운 철판을 평면절삭하는 경우 직진도오차를 최소 로 하는 GAC 방법을 개발하였다.측정은 밀링머시인 자체의 구조적, 동적변화나 절삭 조건의 변화, 공구의 재질 및 마멸상태의 변화, 공작물의 재질 변화등에 적응할 수 있 도록 Fig. 2에 보인 바와 같이 등간격으로 배열된 100개의 위치에서 가공후(post-pro- cess)측정을 통하여 취하였고, 절삭계수의 추정은 측정점을 각각 10개씩 10개의 구간 으로 묶어 각 구간에서의 계의 특성이 변하지 않는다는 가정하에서 계수를 지수가중 반복최소 자승(exponentially weighted recursive least squares, EWRLS)법을 이용하 여 추정하였고, 실제 절삭작업중 모델의 계수변화에 대한 사전 지식이 없이도 이들 계 수들을 보정시킴으로써 최적의 직진도를 얻을 수 있는 절삭조건을 제시하였다. 그리 고 이 방법의 도입으로 단일(SINGLE-PASS)밀링작업이 가능함을 보였고 또한 방법의 타 당성을 증명하기 위하여 여러 경우의 절삭상태에서 실험을 수행하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 춘계학술대회 논문집
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• pp.400-407
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• 1995

The straightness property is one of fundamental geometric tolerances to be strictly controlled for guideways of machine tools and measuring machines. The staightness measurement for long guideways was usually difficult to perform, and it needed additional equipments or special treatment with limited application. In this paper, a new approach is proposed using the profile matching technique for the long guideways, which can be applicable to most of straghtness measurements. An edge of relativelly sthort length is located along a divided section of a long guideway, and the local straightness measurement is performed. The edge is then moved to the next section with several positions overlap. After thelocal straightness profile is measured for every section along the long guideway with overlap, the global straightness profile is constructed using the profile matching technique based on theleast squares method. The proposed techinique is numerically tested for two cases of known global straightness profile arc profile and irregular profile and those profiles with and without random error intervention, respectively. When norandom errors are involved, the constructed golval profile is identical to the original profile. When the random errors are involved, the effect of the number of overlap points are investigated, and it is also found that the difference between the difference between the constructed and original profiles is very close to the limit of random uncertainty with juist few overlap points. The developed technique has been practically applied to a vertical milling machine of moving table type, and showed good performance. Thus the accuracy and efficiency of the proposed method are demonstrated, and shows great potential for variety of application for most of straightness measuirement cases using straight edges, laser optics, and angular measurement equipments.

• Agricultural and Biosystems Engineering
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• 제1권2호
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• pp.100-105
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• 2000

Quality sorting of cut flowers is very essential to increase the value of products. There are many factors that determine the quality of cut flowers such as length, thickness, and straightness of stem, and color and maturity of bud. Among these factors, the straightness of stem and the maturity of bud are generally considered to be more difficult to evaluate. A prototype grading and sorting machine for cut flowers was developed and tested for a rose variety. The machine consisted of a chain-drive feed mechanism, a pneumatic discharge system, and a grading system utilizing color image processing and neural network. Artificial neural network algorithm was utilized to grade cut roses based on the straightness of stem and maturity of bud. Test results showed 89% agreement with human expert for the straightness of stem and 90% agreement for the maturity of bud. Average processing time for evaluating straightness of the stem and maturity of the bud were 1.01 and 0.44 second, respectively. Application of neural network eliminated difficulties in determining criteria of each grade category while maintaining similar level of classification error.

• 한국정밀공학회지
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• 제21권3호
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• pp.155-162
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• 2004

This paper presents the fabrication procedure and the experiments for the 3-axis fine positioning stage proposed in［1］. First, the dynamic characteristics of the actuator and the stage are tested with the preload changed in order to validate the stage design specifications. Secondly, the performance of the stage is also evaluated on the accuracy associated with linear positioning, angular error, and straightness error. Experimental results show that the developed stage is accurate enough to be used for nanometer positioning. Through the analysis and experiment, the developed fine positioning stage are found to have a long stroke due to the magnetically preloaded PZT actuators, the minimum motion crosstalk due to the use of a ball contact mechanism and the compact design.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 추계학술대회 논문집
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• pp.54-59
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• 1998

In order to minimize straightness error of deflected shafts, a automatically bending process control system is designed, fabricated, and studied. The multi-step straightening process and the three-point bending process are developed for the geometric adaptive straightness control. Load-deflection relationship, on-line identification of variations of material properties, on-line springback prediction, and studied for the three-point bending processes. Selection of a loading point supporting condition are derved form fuzzy inference and fuzzy self-learning method in the multi-step straighternign process. Automatic straightening machine is fabricated by using the develped ideas. Validity of the proposed system si verified through experiments.

• 한국기계가공학회지
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• 제10권5호
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• pp.1-6
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• 2011

Machine tool errors have to be characterized and predicted to improve machine tool accuracy. Therefore, it is very important to assess errors in machine tools. Volumetric error analysis has been developed by many researchers. This paper presents a useful technique for analyzing the volumetric errors in machine tools using the ball bar. The volumetric error model is proposed in specific vertical machining center and the program is developed for generating NC code, acquiring the ball bar data, and analyzing the volumetric errors. The developed system assesses the volumetric errors such as positional, straightness, squareness, and back lash. Also this system analyzes the dynamic performance such as servo gain mismatch. The radial data acquired by ball bar on 3D space is used for analyzing these errors. It is convenient to test the volumetric errors on 3D space because all errors are calculated at once. The developed system has been tested using an actual vertical machining center.

• 한국정밀공학회지
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• 제31권12호
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• pp.1133-1139
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• 2014

This paper proposes a simple method to improve a sensitivity of a straightness measurement system for a linear stage, which is applied to a system based on a geometric optic method. An optical system for this method is composed of a corner-cube retro-reflector, a ball-lens and a twodimensional position sensitive detector (2D PSD). The effectiveness of the proposed method was examined theoretically, and verified experimentally using a prototype measurement system. The results show that the measuring sensitivity was dependent on the size of the ball-lens and the setup position of PSD from the ball-lens, and that the proposed method is efficient method to improve the measuring sensitivity.

• Journal of Biosystems Engineering
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• 제24권1호
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• pp.67-74
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• 1999

A prototype cut-flower sorter was developed and tested for its performance with five varieties of roses. Support plates driven by a chain mechanism transported the roses into an image inspection chamber. Color image processing algorithms were developed to evaluate the length, thickness, and straightness of stem and color, height, and maturity of bud. The average absolute errors of the system for the measurements of stem length, stem thickness, and height of bud were 19.7 mm, 0.5 mm, and 3.8 mm, respectively. The results of classification by the sorter were compared with those of a human inspector for straightness of stem and maturity of bud. The classification error for the straightness of stem was 8.6%, when both direct image and reflected image by a mirror were analyzed. The accuracy in classifying the maturity of bud varied among the varieties, the smallest for‘Nobless’(1.5%) and the largest for‘Rote Rose’(13.5%). The time required to process a rose averaged 2.06 seconds, equivalent to the capacity of 1,600 roses per hour.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 춘계학술대회 논문집
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• pp.91-92
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• 2008

• 한국정밀공학회지
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• 제28권8호
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• pp.904-914
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• 2011

The volumetric errors of CNC machining centers are determined by 21 errors, including 3 linear errors, 6 straightness errors, 3 perpendicular errors, 9 angular errors and non-rigid body errors of the machine tool. It is very time consuming and hard to measure all of these errors in which laser interferometer and other parts are used directly. Hence, as many as 21 separate setups and measurements are needed for the linear, straightness, angular and perpendicular errors. In case of the 5-axis machining centers, two more rotary tables are used. It can make 35 error sources of the movement. Therefore, the measured errors of multi movements of the 5-axis tables are very complicated, even if the relative measured errors are measured. This paper describes the methods, those analyze the error sources of the machining centers. Those are based on shifted diagonal measurements method (SDM), R-test and Double ball bar. In case, the angular errors of machine are small enough comparing with others, twelve errors including three linear position errors, six straightness errors and three perpendicular errors can be calculated by using SDM. To confirm the proposed method, SDM was applied to measuring 3 axes of machine tools and compared with directly measurement of each errors. In addition, the methods for measuring relative errors of multi-axis analysis methods using R-test and Double Ball Bar are introduced in this paper.