• 한국정밀공학회지
• /
• 제24권8호통권197호
• /
• pp.89-96
• /
• 2007

In this paper, a new air bearing stage with magnetic preload and a linear motor has been developed for the small precision machine systems. The new air bearing stage is unique in the sense that permanent magnets attached bottom of the iron core of table are used not only for preloading air bearings in vertical direction but also for generating thrust force by current of the coil at base. The characteristics of air bearings using porous pads were analyzed with numerical method, and the magnetic circuit model was derived for linear motor for calculating required preload force and thrust force. A prototype of single axis miniature stage with size of $120(W){\times}120(L){\times}50(H)\;mm^3$ was designed and fabricated and examined its performances, vertical stiffness, load capacity, thrust force and positioning resolution.

• 대한기계학회논문집A
• /
• 제20권12호
• /
• pp.3909-3916
• /
• 1996

Magnetic bearing is the machine element that supports the shaft without mechanical contact using the magnetic force induced by permanent magnet of electromagnet. Active magnetic bearing system is composed of sensor, controller, power amplifier, and electromagnet. If all the elements were dieal, shaft position could be controlled to sensor resolution, Because each elements inreal system have mechanical and electricla losses and nonlinearity, it is impossible to attain the desired performance using general control algorithm. So far it has been studied on improvement of the control algorithm of the electric characteristics of each elements. Another factors to affect shaft behavior are the manufacturing errors due to machine work, and assembling errors due to accumulate manufacturing errors of the radial magnetic bearing. This paper describes that the shaft behavior due to accumulate manufacturing errors and asymmetric bolting. This paper describes that the shaft behavior due to assembling errors of the radial bearings donot affect the rotaitonal accuracy of the shaft. But when the amplitude of the assembling errors increasees over the certain value, the bearing can not support the shaft properly.

• 한국지형학회지
• /
• 제19권2호
• /
• pp.145-159
• /
• 2012

화성 Mawrth Vallis지역의 점토광물을 함유한 층에서 관찰되는 파쇄 패턴의 성인을 파악하기 위해 HiRISE 영상데이터를 활용하여 분석하였다. 함유된 점토광물의 종류에 따라 지표에서 관찰되는 파쇄 패턴에 차이가 나타나는데 논트로나이트를 주로 함유한 지표의 경우 파쇄 패턴이 불규칙적이고 침식을 심하게 받은 상태이나, 몬모릴로나이트를 주로 함유한 층의 지표에는 크기와 형태가 비교적 일관성을 가지는 폴리곤 패턴이 잘 발달되어있다. 이들 폴리곤 파쇄 패턴의 성질은 점토광물 함유층에 따라 달리 해석되는데, 논트로나이트 함유층의 경우 대부분 하중 제거로 인해 발생한 것으로 보이며, 몬모릴로나이트 함유층의 지표에 발달한 파쇄 패턴은 건조 균열로 인해 발생한 것으로 추정된다.

• 한국정밀공학회지
• /
• 제21권4호
• /
• pp.72-78
• /
• 2004

In this paper, a development of an inductive position sensor is described. The sensor is similar to a radial magnetic bearing in that the sensor stator is shaped like a heteropolar magnetic bearing and is driven by a switching amplifier. A demodulation filter extracts the gap information from the switching current ripples. A prototype sensor exhibits the resolution of $0.43\mum$ and the dynamic bandwidth of about 800Hz. The dynamic performance can be improved by increasing the switching frequency. However, the eddy current effects become noticeable at high switching frequency, thus limiting the improvement of the bandwidth.

• International Journal of Precision Engineering and Manufacturing
• /
• 제9권1호
• /
• pp.19-24
• /
• 2008

We propose a new miniature air-bearing stage with a moving-magnet slotless linear motor. This stage was developed to achieve the precise positioning required for submicron-level machining and miniaturization by introducing air bearings and a linear motor sufficient for mesoscale precision machine tools. The linear motor contained two permanent magnets and was designed to generate a preload force for the vertical air bearings and a thrust force for the stage movement. The characteristics of the air bearings, which used porous pads, were analyzed with numerical methods, and a magnetic circuit model was derived for the linear motor to calculate the required preload and thrust forces. A prototype of a single-axis miniature stage with dimensions of $120\;(W)\;{\times}\;120\;(L)\;{\times}\;50\;(H)\;mm$ was designed and fabricated, and its performance was examined, including its vertical stiffness, load capacity, thrust force, and positioning resolution.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.852-857
• /
• 2004

In this paper, an angular self-sensing algorithm is proposed and implemented to a Lorentz force type integrated motor-bearing system. It is based on the principle that the flux linkages of stator windings, calculated from the voltage and torque control current, are the functions of the rotor angle. The tracking angular position error is proven to vanish using the Lyapunov stability method, and the experimental results show that the initial error decays within about 5 seconds. It is found that the resolution of the algorithm remains about 1º over the speed range of 100 to 1000 rpm.

• 한국지구물리탐사학회:학술대회논문집
• /
• 한국지구물리탐사학회 2004년도 대한지구물리학회.한국지구물리탐사학회 공동학술대회 초록집
• /
• pp.308-311
• /
• 2004

• Bulletin of the Korean Chemical Society
• /
• 제15권6호
• /
• pp.497-502
• /
• 1994

A new chiral stationary phase (CSP) for the liquid chromatographic resolution of enantiomers was prepared from (S)-naproxen and 3,5-dinitroaniline. The 6-alkoxy-2-naphthyl group of the CSP was presumed to act as a ${\pi}$-basic interaction site for resolving ${\pi}$-acidic racemates while the 3,5-dinitroanilide group of the CSP was presumed to play a role as a ${\pi}$-acidic interaction site for resolving ${\pi}$-basic racemates. From the chromatographic resolution trends of N-alkylamide derivatives of ${\alpha}$-arylalkylamines on the CSP prepared, the chiral recognition mode involving the intercalation of the amide alkyl chain of the less retained enantiomers between the connecting tethers of the CSP was proposed.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2013년도 추계학술대회 논문집
• /
• pp.63-64
• /
• 2013

Induction motors' faults detection is almost a popular topic among researchers. Monitoring the output of motors is a key factor in detecting these faults. (Short-time) Fourier, (continuous, discrete) wavelet, and extended Park vector transformations are among the methods for fault detection. One major deficiency of these methods is not being able to detect the severity of faults that carry low energy information, e.g. in ball bearing system failure, there is absolutely no way to detect the severity of fault using Fourier or wavelet transformations. In this paper, the authors have applied the Discrete Wavelet Transform (DWT) frequency-domain analysis to detect bearing faults in an induction motor. In other words, in discrete transform which the output signal is decomposed in several steps and frequency resolution increases considerably, the frequency-band analysis is performed and it will be verified that first of all, fault sidebands become more recognizable for detection in higher levels of decomposition, and secondly, the inner race bearing faults turn out easier in these levels; and all these matter because of eliminating the not-required high energy components in lower levels of decomposing.

• 한국음향학회지
• /
• 제22권6호
• /
• pp.482-488
• /
• 2003

선 배열을 이용한 빔 형성시 특정 지향 방향을 기준으로 반대 방향에 동일한 이득을 갖게 되어 수신단에서는 좌/우측 방위구분에 있어 모호성을 갖는다 이에 본 논문에서는 선 배열에 카디오이드 빔을 적용하여 좌/우측 방위 구분의 모호성을 해결하고, 아울러 어레이 합성 처리 기법을 사용하여 음원에 대한 공간적 데이터 수를 증가시키고 음원으로부터 얻은 정보를 코히어런트 합성 처리함으로써 배열 센서가 갖는 공간적인 분해능의 한계를 극복하였다. 시뮬레이션 결과에서는 좌/우측 방위 구분에 대한 성능을 어레이 합성 횟수에 따라 나타내었다.