• 한국기계가공학회지
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• 제3권2호
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• pp.10-17
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• 2004

A real depth of cut in deformed zone has larger than an ideal depth of cut. So the heat generated during grinding operation makes the deformation of a workpiece surface as convex farm. Consequently the workpiece surface remains a geometric error as concave form after cooling In this study, the grinding force and the geometric error were examined in surface grinding. Through magnitude and mode of geometric error were evaluated according to grinding conditions, an optimal grinding condition was proposed to minimize the geometric error In addition, the relationship between the geometric error and the grinding force was examined. Due to least square regression, It was possible to predict the geometric error by using the grinding force.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.341-344
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• 1997

The higher precision in manufacturing field is demanded, the more accurate servo controller is needed. To achieve the high precision, Koren proposed the cross-coupled control (CCC) method. The objective of the CCC is reducing the contour error rather than decreasing the individual axial error. The performance of CCC depends on the contour error model. In this paper we propose a new contour error model which utilizes contour error vector based on parametric curve interpolator. The experimental results show that the new CCC is more accurate than the variable-gain CCC during free-form curve motion.

• ETRI Journal
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• 제32권1호
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• pp.139-141
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• 2010

In this letter, closed-form approximations for outage probability and symbol error rate are presented for a selective decode-and-forward relay network with partial channel information. An independent but not identically distributed Rayleigh fading environment is considered. Numerical and simulated results demonstrate the validity of the analytical results.

• 한국정밀공학회지
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• 제19권4호
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• pp.124-131
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• 2002

In this paper, an extended volumetric error model considering backlash in a three-axis machine tool was proposed and utilized for calculating the volumetric error of the machine tool at any position in three-dimensional workspace. Backlashes are interrelated; i.e. the angular backlash affects the straightness errors which then affect talc calculated squareness errors. Therefore, a new concept was introduced to define the backlash of squareness errors to incorporate the backlash of squareness error into the volumetric error, and the characteristics of the backlash of squareness error were investigated. The effects of backlash errors were assessed, by experiments. for 21 geometric errors of a machine tool. The backlash error was shown to be one of the systematic errors of a machine tool. And a generalized volumetric error model formulator for three-axis machine tools was developed, which allowed us to formulate machine tool synthesis error models far all possible machine tool configurations only with machine tool topology information. Based on these volumetric error model and model formulator, a computer-aided volumetric error analysis system was developed for a three-axis machine tool in this paper. Then the volumetric error at an arbitrary position can be obtained, and displayed in a three-dimensional graphic form.

• 한국항해항만학회지
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• 제37권4호
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• pp.329-335
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• 2013

This paper is to develop the position error equations including the attitude errors, the errors of nadir and ship's heading, and the errors of ship's position in the free-gyro positioning and directional system. In doing so, the determination of ship's position by two free gyro vectors was discussed and the algorithmic design of the free-gyro positioning and directional system was introduced briefly. Next, the errors of transformation matrices of the gyro and body frames, i.e. attitude errors, were examined and the attitude equations were also derived. The perturbations of the errors of the nadir angle including ship's heading were investigated in each stage from the sensor of rate of motion of the spin axis to the nadir angle obtained. Finally, the perturbation error equations of ship's position used the nadir angles were derived in the form of a linear error model and the concept of FDOP was also suggested by using covariance of position error.

• 대한전자공학회논문지SP
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• 제39권4호
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• pp.470-476
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• 2002

본 논문에서는 순환 DFT 기반의 위상 측정 알고리즘을 구현함에 있어서 계수 근사 및 주파수 변이에 따른 성능 열화를 해석하였다. 오차의 영향을 해석하기 위해서 근사 순환 DFT식을 이용하여 오차 방정식(error dynamics)을 정의하고 이의 통계적 특성을 이용하여 오차의 특성을 분석한다. 오차 전력은 오차파급의 주요 영향 요소인 근사 bit수, DFT 구간 길이와 잡음에 관한 closed-form으로 유도되어 진다. 해석적으로 유도한 식과 시뮬레이션 실험을 통해 얻을 결과를 비교하여 타당성을 확인하였다.

• 대한방사선치료학회지
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• 제27권2호
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• pp.157-166
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• 2015

목 적 : 사이버나이프 종양 추적 시스템(Cyber-knife tumor tracking system)은 환자 외부에 부착한 LED marker에서 얻어진 실시간 호흡 주기 신호와 호흡에 따라 움직이는 종양의 위치와의 상관관계를 바탕으로 종양의 위치를 미리 예측하고 종양의 움직임을 치료기와 동기화 (Synchronize) 시켜 실시간으로 종양을 추적하며 치료하는 시스템이다. 본 연구의 목적은 사이버나이프 종양 추적 방사선 치료 중 기침이나 수면 등으로 인해 예측 불가능한 갑작스러운 호흡 형태 변화에 따른 종양 추적 방사선 치료 시스템의 정확도를 평가하고자 한다. 대상 및 방법 : 연구에 사용된 호흡 Log 파일은 본원에서 호흡 동조 방사선치료(Respiratory gating radiotherapy)나 사이버나이프 호흡 추적 방사선수술(Cyber-knife tracking radiosurgery)을 받았던 환자의 호흡 Log 파일을 바탕으로, 정현곡선 형태(Sinusoidal pattern)와 갑작스런 변화 형태(Sudden change pattern)의 Log 파일을 이용하여 측정이 가능하도록 재구성하였다. 재구성 된 호흡 Log 파일을 사이버나이프 동적 흉부 팬텀에 입력하여 호흡에 따른 움직임을 구현할 수 있도록 기존 동적 흉부 팬텀의 구동장치를 추가 제작하였고, 호흡의 형태를 팬텀에 적용 시킬 수 있는 프로그램을 개발하였다. 팬텀 내부 표적(Ball cube target)의 움직임은 호흡의 크기에 따라 상하(Superior-Inferior)방향으로 5 mm, 10 mm, 20 mm 3가지 크기의 변위로 구동하게 하였다. 팬텀 내부 표적에 EBT3 필름 2장을 교차 삽입하여 표적 움직임의 변화에 따라 사이버나이프 제조사에서 제공된 End-to-End(E2E) test를 호흡의 형태에 따라 각각 5회씩 실시하고 측정하였다. 종양 추적 시스템의 정확도는 삽입된 필름을 분석하여 표적 오차(Targeting error)로 나타내었고, 추가로 E2E test가 진행되는 동안 상관관계 오차(Correlation error)를 측정하여 분석하였다. 결 과 : 표적 오차는 정현곡선 호흡 형태일 경우 표적 움직임의 크기가 5 mm, 10 mm, 20 mm 에 따라 각각 평균 $1.14{\pm}0.13mm$, $1.05{\pm}0.20mm$, $2.37{\pm}0.17mm$이고, 갑작스런 호흡 변화 형태일 경우 각각 평균 $1.87{\pm}0.19mm$, $2.15{\pm}0.21mm$, $2.44{\pm}0.26mm$으로 분석되었다. 표적 추적에 있어 변위 벡터의 길이로 정의할 수 있는 상관관계 오차는 정현곡선 호흡 형태일 경우 표적 움직임의 크기가 5 mm, 10 mm, 20 mm 에 따라 각각 평균 $0.84{\pm}0.01mm$, $0.70{\pm}0.13mm$, $1.63{\pm}0.10mm$이고, 갑작스런 호흡 변화 형태일 경우 각각 평균 $0.97{\pm}0.06mm$, $1.44{\pm}0.11mm$, $1.98{\pm}0.10mm$으로 분석되었다. 두 호흡 형태에서 모두 상관관계 오차 값이 클수록 표적 오차 값이 크게 나타났다. 정현곡선 호흡 형태의 표적 움직임 크기가 20 mm 이상일 경우, 두 오차 값 모두 사이버나이프 제조사의 권고치인 1.5 mm 이상으로 측정되었다. 결 론 : 표적 움직임의 크기가 클수록 표적 오차 값과 상관관계 오차 값이 증가하는 경향이 있었으며, 정현곡선 호흡 형태보다 갑작스런 호흡 변화 형태에서 오차 값이 크게 나타났다. 호흡의 형태가 규칙적인 정현 곡선 형태더라도 표적의 움직임이 클수록 종양 추적 시스템의 정확도가 감소하는 것으로 판단할 수 있다. 사이버나이프 종양 추적 시스템의 알고리즘을 이용하여 치료 시행 시 환자의 기침 등으로 인하여 갑작스럽게 예측 불가능한 호흡 변화가 있는 경우 치료를 멈추고 내부 표적 확인 과정을 재실시 하여야 하며 호흡 형태를 재조정해야 할 필요가 있다. 치료 중 환자가 본인의 호흡 형태를 관찰 할 수 있는 고글 모니터 등을 착용하여 규칙적인 호흡 형태를 유도하는 것이 치료의 정확도는 향상될 수 있다고 판단된다.

• 한국운동역학회지
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• 제16권4호
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• pp.95-103
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• 2006

The purpose of this study was to review the relevant literature about coaching and thereupon, survey the coaching methods used for golf lesson to reinterpret them and thereby, describe in view of kinetics the swing errors committed frequently by amateur golfers and suggest more scientific golf coaching methods. For this purpose, kinetic elements were divided into accuracy and power ones and therewith, the variables affecting such elements were identified. For this study, a total of 60 amateur golfer were sampled, and their swing forms were photographed with two high-speed digital cameras, and the resultant images were analyzed to determine the errors of each form kinetically, which would be analyzed again with the program V1-5000. The kinetic elements could be identified as accuracy, power and accuracy & power. Thus, setup and trajectory were classified into accuracy elements, while differences of inter-joint angles, cocking and delayed hitting. Lastly, timing and axial movement were classified into accuracy & power elements. Three errors were identified in association with setup. The errors related with trajectory elements accounted for most (6) of the 20 errors. Three errors were determined for inter-joint angle differences, and one error was associated with cocking and delayed hitting. Lastly, one error was classified into timing error, while five errors were associated with axial movement. Finally, as a result of arranging the errors into a cross table, it was found that the errors were associated with each other between take-back and back-swing, take-back and follow-through, back-swing and back-swing top, and between back-swing and down-swing. Namely, an error would lead to other error repeatedly. So, it is more effective to identify all the errors for every form and correct them comprehensively rather than single out the errors and correct them one by one.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.676-680
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• 2000

In this paper, an extended volumetric error model considering backlash in a three-axis machine tool was proposed and utilized for calculating the volumetric error of the machine tool at any position in three-dimensional workspace. Backlashes are interrelated; i.e. the angular backlash affects the straightness errors which then affect the calculated squareness errors. Therefore, a new concept was introduced to define the backlash of squareness errors to incorporate the backlash of squareness error into the volumetric error, and the characteristics of the backlash of squareness error were investigated. The effects of backlash errors were assessed, by experiments, fur 21 geometric errors of a machine tool. The backlash error was shown to be one of the systematic errors of a machine tool. Based on this volumetric error model, a computer-aided volumetric error analysis system was developed for a three-axis machine tool in this paper. Then the volumetric error at an arbitrary position can be obtained, and displayed in a three-dimensional graphic form.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.224-227
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• 2001

Adaptive analysis of multilayered composite and sandwich plates is carried out. The adaptive analysis is based on a finite element error form, which measures the difference between the through-the-thickness distribution of finite element displacement and the actual displacement. The region where the error-measure exceeds the prescribed admitted error value, the finite element mesh locally refined in the thickness direction using the mesh superposition technique. Several numerical tests are conducted to validate the effectiveness of the current approach for adaptive analysis of laminated plates.