• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.422-422
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• 2000

Parallel manipulators have been used to a variety of applications, including the motion simulators and mechanism for precise machining. A Stewart-Gough type parallel manipulator is composed of six linear joints which have wider contact areas than revolute ones, so linear joints are more affected by frictional force. First, the reference trajectories are computed from the model of the parallel manipulator assuming that it is subject to only the gravitational force and no friction exists. In the actual operation where friction exists, the control inputs, which correspond to the friction forces, are obtained by forcing the actual joint variables to follow these trojectories by proper control. It is shown that control performance can be improved when the friction compensation based on this information is added to the controller for position control of the moving plate of a parallel manipulator.

• 제어로봇시스템학회논문지
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• 제11권7호
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• pp.609-614
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• 2005

Parallel manipulators have been used for a variety of applications, including the motion simulators and mechanism for precise machining. Since the ball screws used for linear motion of legs of the Stewart-Gough type parallel manipulator provide wider contact areas than revolute joints, parallel manipulators are usually more affected by frictional forces than serial manipulators. In this research, the method for detecting the frictional forces arising in the parallel manipulator using the gravitational force is proposed. First, the reference trajectories are computed from the dynamic model of the parallel manipulator assuming that it is subject to only the gravitational force without friction. When the parallel manipulator is controlled so that the platform follows the computed reference trajectory, this control force for each leg is equal to the friction force arising in each leg. It is shown that control performance can be improved when the friction compensation based on this information is added to the controller for position control of the moving plate of a parallel manipulator.

• 공학교육연구
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• 제21권3호
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• pp.12-19
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• 2018

In this study, a new experimental device was developed for measurement of the coefficient of kinetic friction using a photo gate timer system which have advantages of easy and accurate detection of motion. This device, consisting of a side air-guide track and a side friction-free glider, forces a friction sample to move in a straight line without producing unnecessary friction. The new device is compared to two conventional measuring methods of friction for four different friction samples: one is using a camera system and the other is using a force sensor. It is demonstrated that the developed friction device in this study is easier to operate and produces the most accurate and the least deviating results among them. On the basis of these results, we propose that friction experiment using the new friction device is included in general physics experiment, so that engineering students should have a chance to get correct understanding of classical mechanics including friction phenomenon.

• Tribology and Lubricants
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• 제11권5호
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• pp.128-135
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• 1995

Atomic force microscopy/friction force microscopy (AFM/FFM) techniques are increasingly used for tribological studies of engineering surfaces at scales, ranging from atomic and molecular to microscales. These techniques have been used to study surface roughness, adhesion, friction, scratching/wear, indentation, detection of material transfer, and boundary lubrication and for nanofabrication/nanomachining purposes. Micro/nanotribological studies of single-crystal silicon, natural diamond, magnetic media (magnetic tapes and disks) and magnetic heads have been conducted. Commonly measured roughness parameters are found to be scale dependent, requiring the need of scale-independent fractal parameters to characterize surface roughness. Measurements of atomic-scale friction of a freshly-cleaved highly-oriented pyrolytic graphite exhibited the same periodicity as that of corresponding topography. However, the peaks in friction and those in corresponding topography were displaced relative to each other. Variations in atomic-scale friction and the observed displacement has been explained by the variations in interatomic forces in the normal and lateral directions. Local variation in microscale friction is found to correspond to the local slope suggesting that a ratchet mechanism is responsible for this variation. Directionality in the friction is observed on both micro- and macro scales which results from the surface preparation and anisotropy in surface roughness. Microscale friction is generally found to be smaller than the macrofriction as there is less ploughing contribution in microscale measurements. Microscale friction is load dependent and friction values increase with an increase in the normal load approaching to the macrofriction at contact stresses higher than the hardness of the softer material. Wear rate for single-crystal silicon is approximately constant for various loads and test durations. However, for magnetic disks with a multilayered thin-film structure, the wear of the diamond like carbon overcoat is catastrophic. Breakdown of thin films can be detected with AFM. Evolution of the wear has also been studied using AFM. Wear is found to be initiated at nono scratches. AFM has been modified to obtain load-displacement curves and for nanoindentation hardness measurements with depth of indentation as low as 1 mm. Scratching and indentation on nanoscales are the powerful ways to screen for adhesion and resistance to deformation of ultrathin fdms. Detection of material transfer on a nanoscale is possible with AFM. Boundary lubrication studies and measurement of lubricant-film thichness with a lateral resolution on a nanoscale have been conducted using AFM. Self-assembled monolyers and chemically-bonded lubricant films with a mobile fraction are superior in wear resistance. Finally, AFM has also shown to be useful for nanofabrication/nanomachining. Friction and wear on micro-and nanoscales have been found to be generally smaller compared to that at macroscales. Therefore, micro/nanotribological studies may help def'me the regimes for ultra-low friction and near zero wear.

• 전자공학회논문지A
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• 제30A권3호
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• pp.130-138
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• 1993

A mechanism for collision detection in general animation system is necessary to prevent the interpenetration among multiple objects. On the other hand, a dynamic simulation system which is a part of animation system simulates realistic motions using dynamics after the collision, which is called collision response. In this paper, a method for reducing the CPU time for collision detection by removing redundant calculations and object sorting is proposed. A dynamic simulation system including collision detection and response function was implemented to demonstrate the proposed methods, where the input data as elasticity, friction, gravity, object shape, external force and external torque are given by the user. The system simulates motions of multiple objects using dynamics, and generates the wireframe display.

• 대한기계학회논문집B
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• 제37권6호
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• pp.545-550
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• 2013

본 논문은 정전기력을 이용한 마찰력 변조를 이용하여 손끝을 통한 촉각정보의 입출력을 동시 구현하는 소자를 제안하였다. 기존의 촉각소자들이 촉각정보의 입력 및 출력을 개별적으로 구현한 것에 비해 본 연구는 손끝의 수직/수평 방향 동작 인식과 질감 구현을 동시에 구현하였다는 점에서 차별성을 가진다. 실험분석을 통해 검증한 손끝 동작 인식기능은 수직방향의 클릭의 경우 0.146nF/$40{\mu}m$, 수평방향의 경우 0.09nF/$750{\mu}m$의 정전용량 변화를 통해 인식 가능하였으며, 질감 구현의 경우 정전기적 인력을 통해 마찰력을 32~152mN의 범위에서 제어할 수 있음을 확인하였다. 교류전압을 이용한 수평적 진동은 60V, 3Hz에서 최대 128.1mN의 마찰력 변조를 구현하였으며, 이는 기존 연구 대비 32% 향상을 보여준다. 본 연구는 손끝에서 정보의 입출력을 동시 구현하여 정보기기의 촉각인터페이스에 적용 가능하다.

• 한국정보통신학회논문지
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• 제25권12호
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• pp.1874-1881
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• 2021

폭설로 인한 도로 미끄러짐과 함께 영하의 기온으로 도로와 차량 통행용 다리, 터널 출입구 쪽에서 주로 발생하는 블랙아이스는 운전자의 시야에서는 아스팔트의 이미지가 투과되어 보이기에 잘 인식되지 않아서 자동차들이 미끄러지는 (슬립 현상) 상황을 발생시키기에 차량이 제동력을 잃어서, 대형 교통사고로 이어져 심각한 인명과 재산상 손실을 초래하고 있다. 본 논문에서는 기존에 연구되었던 블랙아이스 감지 방법들(인공위성 촬영, 초음파 수신으로 미끄러짐의 패턴을 확인, 도로 표면의 온도측정, 차량 주행 중 타이어의 마찰력 차이를 확인하기)의 단점들을 보완하고, 블랙아이스를 감지하는 센서의 크기를 줄여서 많은 이동체에 적용할 수 있도록 하고자 적외선 카메라를 이용하여 도로 상태를 확인하고, 이 정보를 딥러닝 학습을 통하여 블랙아이스를 판별하는 방법을 제안하고자 한다.

• 한국자기학회지
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• 제24권6호
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• pp.171-178
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• 2014

전자기를 이용하여 배관의 비파괴검사를 적용하는 방법 중 하나인 Remote Field Eddy Current Testing (RFECT)는 큰 마찰력이 발생하고 잔류자화성분이 남는 Magnetic Flux Leakage (MFL) 방식과 외벽의 결함을 측정하는데 곤란한 일반 Eddy Current Testing (ECT) 방식의 단점들을 보완할 수 있는 기법으로 50여 년 전부터 다양한 기관에서 연구되어왔다. 그러나 배관 내에서 발생하는 와전류와 자기장에 대한 연구와 RFECT Exciter Coil의 설계에 대한 논의가 부족한 실정이다. 본 논문에서는 유한요소법을 이용한 전자기 해석을 통해 배관 내에서 발생하는 와전류와 자기장의 분포를 확인하고 변수 변화에 따른 영향을 분석하였다. 또한 Exciter Coil에 대한 최적 설계 알고리즘을 제시하고, 결함 형상과 기타 변수 변화가 결함신호에 미치는 영향을 확인하였다.