• Information and Communications Magazine
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• v.33 no.10
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• pp.65-70
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• 2016

최근 스마트폰의 이용 사례가 증가함에 따라, 스마트폰에 내장되어 있는 다양한 센서를 이용하여 인간의 행동을 인식하기 위한 연구가 많은 각광을 받고 있다. 본고에서는 인간의 기본적인 행동 중에 앉기, 걷기, 달리기 등의 행동 특성을 스마트폰에 내장되어 있는 3축 가속도 센서를 통하여 분석하고 인간의 기본적 행동을 자동으로 인식하기 위한 방법에 대하여 비교 분석하는 것을 목적으로 한다. 구체적으로는 스마트폰에 내장되어 있는 3차원 가속도 센서로부터 추출된 데이터를 시간축에서 샘플링하여 인간의 행동을 인식하기 위한 기댓값 최대화 알고리즘, 랜덤 포레스트, 딥러닝 기반의 기계학습 방법을 비교하여 각 기계학습 알고리즘의 장단점을 분석한다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.683-689
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• 1996

5축 가공기는 가공중의 공구자세 변화를 요구하는 복잡한 산업형상의 가공, 혹은 경사 가공을 통한 표면조도 향상등의 목적으로 채용되는 첨예의 공작기계로서 이를 지원하는 CAM연구가 활발히 이루어지고 있다. 그러나, 산업현장에서 흔히 5축 가공기로 일컬어지는 상당수의 5축 가공기는 기구축은 5축을 가지나, 동기제어 축수는 3측인 “선택적 3/5축 가공기”의 형태로서 진정한 의미의 5축가공기와는 근본적으로 다르다. 5축 동기제어를 지원하는 CAM연구는 부분적으로 연구 개발된 상태이나, 선택적 3/5축을 지원하는 CAM 이론은 연구된 바 없으며, 이에 따라 현장에서는 공작물의 셋업을 변경시키는 소위 자동 인덱싱 방식으로 활용하고 있는 실정이다. 본 연구팀에서는 선택적 3/5축 가공기에서 5축 가공을 실현할 수 있는 공구경로 산출 및 제어알고리즘을 개발하고 있으며, 본 논문에서는 (5축 가공 대비) 선택적 3/5축 가공문제의 이론적 특성과 경사가공을 수행하기 위한 알고리즘을 소개하고 시뮬레이션을 통하여 유효성을 보인다.

• Progress in Medical Physics
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• v.7 no.1
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• pp.53-64
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• 1996

Purpose: The purposes of this paper are to develop a theoretical basis that the beam directions should be considered when the mechanical accuracy of teletherapy machine is evaluated by the star pattern test, to develop methods using asymmetric field in length to simulate beam direction for the case that beam direction does not appear on film. Method: In evaluating mechanical rotational accuracy of the gantry of teletherapy unit by the star pattern test, the direction of radiation beams was considered. A star pattern using some narrow beams was made. Density profiles at 10cm far from estimated gantry axis on the star pattern were measured using an optical densitometer. On each profile, one coordimate of a beam axis was determined. A pair of coordinates on a beam axis form an equation of the axis. Assume that a unit vector equation omitted is with same direction as radiation beam and a vector equation omitted is a vector directing to the beam axis from the estimated gantry axis. Then, a vector product equation omitted ${\times}$ equation omitted is an area vector of which the absolute value is equal to the distance from the estimated gantry axis to the beam axis. The coordinate of gantry axis was obtained by using least-square method for the area vectors relative to the average of whole area vectors. For the axis, the maximum of absolute value of area vectors would be an accuracy of the gantry rotation axis. For the evaluation of mechanical accuracies of collimator and couch axes for which beam direction could not be depicted on a star pattern test film, narrow beams asymmetric in field length was used to simulate beam direction. Result: For a star test pattern to evaluate the mechanical accuracy of rotational axes of a telectherapy machine, the result considering beam direction was different from that ignoring beam direction. For the evaluation of mechanical accuracies of collimator and couch axes by means of a star pattern test, narrow asymmetric beams could simulate beam direction. Conclusion: When a star pattern test is used to evaluate the mechanical accuracy of a teletherapy unit, beam direction must be considered or simulated, and quantitatively evaluated.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1990.06a
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• pp.45-52
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• 1990

고도의 신뢰도를 요구하는 정밀기계의 보편화는 트라이볼로지 요소중에서 밀봉기능에 관련된 시일의 해석 및 설계가 커다란 관심사로 부각되었다. 특히 고속회전을 요하는 경우에 대한 회전 시스템의 동적 안정성은 대단히 중요하다. 미끄럼 접촉운동을 하고 있는 기계평면시일의 시일링 간극은 대단히 작기 때문에 시일의 접촉면에서 형상이 변화하게 되면 시일 성능은 커다란 영향을 받게 된다. 시일의 접촉표면 가공시 발생되는 평면도(flatness), 조립시의 회전축과 시일축 사이의 중심 맞추기의 어려움, 회전축의 자중량 등 때문에 발생되는 회전링 사이의 상대적인 경사도(misalignment)는 시일의 동적 불안정성에 영향을 준다. 또한 상대 접촉 운동면에서 경계 또는 고체 마찰에 의한 마멸의 진행은 시일의 코닝(coning) 현상을 일으킨다. 본 연구에서는 비압축성 유체가 온도의 영향을 받아 점도가 선형적으로 변화하는 경우에 대한 시일링 간극 내에서의 압력분포를 유한차분법을 이용하여 해석하였다. 여기서 얻어진 결과를 이용하여 시일의 축력과 모우멘트를 해석함으로써 시일의 동적 불안정성에 대하여 논하였다. 이 때 기계평면 시일의 형상은 코닝이 있고, 시일의 중심축이 경사진 경우를 고려하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.1
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• pp.97-103
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• 2013

This study proposes a path generation technique for simultaneous five-axis driving for ball bar measurement, which is equivalent to cone frustum machining as mentioned in the NAS979 standard. The technique is generalized for a 3D circular path, and it is applicable to all machine tools regardless of their structural configurations. A mathematical machine input model that consists of a five-axis machine tool, ball-bar measurement and conical path information as inputs is presented for easy NC code generation, simulation for various test conditions, and a measurement test. The movement range of rotary axes, which depends on various conditions, is mathematically analyzed based on the proposed conical path model. Moreover, the effect of the movement range on various conditions (apex angle and inclination angle, ball bar tilting acceptance angle, offset position of workpiece ball, etc.) is analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.165-171
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• 2012

In this paper, an analytical method is used to perform a sensitivity analysis of geometric errors in a three-axis machine tool. First, an error synthesis model is constructed for evaluating the position volumetric error due to the geometric errors, and then an output variable is defined, such as the magnitude of the position volumetric error. Next, the global sensitivity analysis is executed using an analytical method. Finally, the sensitivity indices are calculated using the quantitative values of the geometric errors.

• Aerospace Engineering and Technology
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• v.9 no.2
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• pp.138-142
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• 2010

The thrust axis alignment of the launch vehicle is very important because of the misalignment causes the unstable attitude control and results in mission failure. Generally, optical methods such as digital theodolite and laser tracker and mechanical method such as turn table method are used to align thrust axis to vehicle axis. This article deals with the simple method of thrust axis alignment of Kick Motor.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.6
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• pp.783-790
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• 2013

Circular path generation for ball bar measurement using the simultaneous movement of two axes with at least one rotary axis requires the execution of CAM software. However, a change in the machine type or measurement condition requires a new execution of the CAM software, which is cumbersome. This paper presents a circular path generation technique that does not require CAM software and is applicable to different types of driving axes with an arbitrary structural configuration of machine tools and any ball bar setup condition. Mathematical equations are derived for three cases using the proposed technique. In addition, to inspect the measurement feasibility for avoiding physical interference among the ball bar parts, a tilting angle calculation is proposed. The validity of the proposed technique was verified by performing a ball bar experiment with A and C as the simultaneous axes of a five-axis machine tool.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.4
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• pp.16-23
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• 2021

Currently, 6-axis articulated robots are used throughout the industry because of their 6-dof (degrees of freedom) and usability. However, 6-axis articulated robots have a fixed base and their movements are limited by the rotational operating range of each axis. If the angle of the 2-axis additional axes can be adjusted according to the position and orientation of the end-effector of the 6-axis articulated robot, the effectiveness of the 6-axis articulated robot can be further increased in areas where the angle is important, such as welding. Therefore, in this paper, we proposed a cooperative kinematic inter-operation strategy. The strategy will be verified using the Simulink of MATLABⓇ, an engineering program, and RecurdynⓇ, a dynamic simulation program.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.36-43
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• 2004

In this paper, the frequency spectra from respective mechanical noise signals detected using ultrasonic wave and AE(Acoustic Emission) sensor were analysed to under spark generation between brush and commutator side with arbitrarily 15$^{\circ}$ rotation for brush from the DC motor in operation. Also, the frequency spectra from respective magnetizing noise signals detected using ultrasonic wave and AE sensor were analysed to under neutral point for brush from the DC motor in normal operation. And the analyses and comparison between the mechanical noise signal and magnetizing noise signal of ultrasonic wave with brush location change from the DC motor in operation. As the experimental results, tile mechanical noise signal of ultrasonic wave under spark generation between brush and commutator side with brush location change from the DC motor in operation were increased about 2.5∼3.0 times than magnetizing noise signal of ultrasonic wave form the DC motor in normal operation. Also, the main frequency band for mechanical noise signals of AE under spark generation between brush and commutator side with brush location change from the DC motor in operation, appeared about 1.3[MHz]∼l.5[MHz] by the fast fourier transform.