• Journal of KIISE:Software and Applications
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• v.26 no.10
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• pp.1193-1203
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• 1999

본 논문에서는 한글과 영문 문서 영상들에 대한 기울어짐 추정(skew estimation) 알고리즘을 제안한다. 제안 방법은 전체 문서 영상에서 텍스트 요소들이 밀집되어 있는 영역을 선별하고, 선별된 영역에 대해 허프 변환을 적용하는 선택적 주의집중(selective attention) 방식을 채택한다. 제안 방법의 기울기 추정 과정은 2단계로 구성되는데, coarse 단계에서는 전체 영상을 몇 개의 영역으로 나누고 동일한 영역에 속하는 데이타들간의 연결 각도를 계산하여 각 영역별 accumulator에 저장한다. accumulator에 저장된 빈도치를 기준으로 $\pm$45$^{\circ}$범위 내에서 최대 $\pm$1$^{\circ}$의 오차를 가진 각 영역별 기울기를 계산한 후, 이들 중 최대 빈도값을 갖는 영역을 선정하고 그 영역의 기울기 각도를 문서 영상의 대략적인 기울기 각도로 결정한다. Refine 단계에서는 coarse 단계에서 선정된 영역에 허프 변환을 적용하여 정확한 기울기를 계산하는데, coarse 단계에서 추정한 기울기의 $\pm$1$^{\circ}$범위 내에서 0.1$^{\circ}$간격으로 측정한다. 이와 같은 선택적 주의집중 방식을 통해 기울기 추정에 소요되는 시간 비용은 최소화하고, 추정의 정확도는 최대화 할 수 있다.제안 방법의 성능 평가를 위한 실험은 다양한 형태의 영문과 한글 문서 영상 2,016개에 적용되었다. 제안 방법의 평균 수행 시간은 Pentium 200MHz PC에서 0.19초이고 평균 오차는 $\pm$0.08$^{\circ}$이다. 또한 기존의 기울기 추정 방법과 제안 방법의 성능을 비교하여 제안 방법의 우수성을 입증하였다.Abstract In this paper we propose a skew estimation algorithm for English and Korean document images. The proposed method adopts a selective attention strategy, in which we choose a region of interest which contains a cluster of text components and then apply a Hough transform to this region. The skew estimation process consists of two steps. In the coarse step, we divide the entire image into several regions, and compute the skew angle of each region by accumulating the slopes of lines connecting any two components in the region. The skew angle is estimated within the range of $\pm$45 degree with a maximum error of $\pm$1 degree. Next we select a region which has the most frequent slope in the accumulators and determine the skew angle of the image roughly as the angle corresponding to the most frequent slope. In the refine step, a Hough transform is applied for the selected region within the range of $\pm$1 degree along the angle computed from the coarse step, with an angular resolution of 0.1 degree. Based on this selective attention strategy, we can minimize the time cost and maximize the accuracy of the skew estimation.We have measured the performance of the proposed method by an experiment with 2,016 images of various English and Korean documents. The average run time is 0.19 second on a Pentium 200MHz PC, and the average error is $\pm$0.08 degree. We also have proven the superiority of our algorithm by comparing the performance with that of other well-known methods in the literature.

• Journal of Magnetics
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• v.16 no.4
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• pp.417-422
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• 2011

This paper presents the characteristics of PM eddy current loss and harmonic iron loss for PM step-skewed Interior Permanent Magnet Synchronous Motor (IPMSM) with concentrated windings and multi-layered PM under the running condition of maximum torque per ampere (MTPA) and flux-weakening control. In particular, PM eddy current loss and harmonic iron loss in IPMSM have been numerically computed with three-dimensional Finite Element Analysis (3D FEA), whereby IPMSM with concentrated windings and multi-layered PM has been designed to identify the optimized skew angle contributing to the reduced PM eddy current loss and torque ripples, while maintaining the required average torque. Furthermore, numerical investigation on PM eddy current loss and iron loss at MTPA and flux-weakening control has been carried-out in terms of PM step-skew.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.326-328
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• 2000

The paper proposes the scheme of skew detection for Thai printed document images by using linear regression algorithm. It intends to use with the Thai character recognition systems to reduce the skew detection time. This scheme begins by finding the center of gravity of a document image. This point is used as the starting point for gathering data in the scheme. The data is obtained by scanning incrementally one pixel in vertically with the width of 20-pixels. After the scanning process, if data Is different from it's neighbor more than ${\pm}$ 15 pixels, it will be considered as noise or data in other lines and will be deleted. The last step is the operation by using linear regression algorithm on these selected data and the skew angle will be obtained. The proposed method has been tested with 45 document images with different fonts, sizes and skew angles. The experiment results show that the proposed method can detect the skew angle with the error of less then one degree. The average processing time is about 19 times faster than that of the Hough Transform method.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.132-134
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• 2005

The severe problem in improving the positioning precision of a permanent linear synchronous motor(PMLSM) is the large detent force caused by the PM. It is generally an undesired effect that contributes to the torque ripple, vibration and noise of machine. In this paper, the method to reduce detent force according to the mover skew is studied and analyzed using the analytical method. The analytical results are validated by finite clement analyses.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1923-1929
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• 2009

The design of SPMSM(surface mounted permanent magnet synchronous motor) has been performed to reduce cogging torque and torque ripples. In general, cogging torque and torque ripples are affected by the shapes of teeth width, yoke depth, magnet pole arc, etc. Particularly, the minimum design point of cogging torque and torque ripples are different so that the design of SPMSM should be done to compromise both of them for precision application. In this paper, the design of PMSM for EPS(electric power steering) system is performed to verify the validity, and the design characteristics versus teeth width, yoke depth, and magnet pole arc are investigated in order to find out the minimum point of cogging torque and torque ripples. In addition, skew of PM is applied for cogging torque reduction.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.76-81
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• 2010

본 논문에서는 카메라를 이용하여 크레인 스프레더의 스큐모션을 계측하는 계측기법에 대해 고찰하고 있다. 계측장치는 트롤리에 설치한 카메라와 스프레더에 설치한 두 개의 랜드마크로 구성된다. 랜드마크를 이용하여 크레인 스프레더 흔들림과 상하위치를 검출하는 기법은 저자들이 이미 제안한 기술이며 실험을 통해 그 유용성을 검증하였다. 크레인 스프레더의 스큐모션 계측기법 또한 제안된 계측기법에 기초한 것으로 두 개의 랜드마크를 검출하여 템플릿 매칭기법으로 스큐모션을 계측할 수 있다. 스큐모션은 스프레더의 회전각도를 검출하여 계측해야 하는데 계측정도와 신뢰도는 정확한 템플릿매칭의 가능여부에 의존하게 된다. 즉, 랜드마크의 회전으로 매칭이 실패할 경우에는 정확한 회전각도를 검출할 수 없는 경우가 발생할 수 있게 된다. 따라서 본 논문에서는 랜드마크 회전에 따라 템플릿을 회전시키는 방법을 도입하여 템플릿매칭의 신뢰성과 계측정도를 개선하는 방법에 대해 연구하였다. 제안된 방법을 이용할 경우 템플릿매칭이 실패하는 경우가 없음을 실험을 통해 확인하였으며, 측정범위는 ${\pm}12^{\circ}$ 이고 이것은 크레인 스프레더의 스큐모션을 파악하고 제어하는데 충분한 정도의 범위이다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.7
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• pp.75-80
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• 2014

The small wind turbines has the merits of setting up with low costs by individuals, and get the energy saving effects that, it has the secured, separate markets from the big range systems, and the developing of it is continuously proceeding. The objective of this paper is to provide the design characteristics analysis of a permanent magnet synchronous generator(PMSG) skewed for magnet of rotor, the main advantage to be explored with the use of a split core design is the reduction in manufacturing costs and its simplicity in manufacture, compared to the manufacturing costs of a core skew PM machine. This thesis is aiming mainly analyzing the characteristics of the prototype to verify through Finite Element Method(FEM) and tests.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.579-580
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• 2008

DRAM설계시 DDR2에서부터 고속 동작으로 인해 반송파에 의한 신호외곡으로 impedance matching의 필요성이 대두되었다. 이로 인해 제안된 방법은 외부 Termination 저항(RZQ)을 기준으로 impedance matching을 위한 Rtt 저항의 생성이다.[1] 제안된 ZQ Calibration 회로는 기존의conventional ZQ Calibration 회로에 After ZQ calibration block을 추가하여 한 번 더 교정함으로써 마지막 PMOS Array와 NMOS Array 저항 값이 Termination 저항 값에 가깝도록 설계하였다. 따라 전력효율은 그대로 유지하면서 ${\Delta}VM$의 오차범위를 기존의 ${\pm}5%$이내에서 skew 조건에 따라 ${\pm}1.33%$까지 향상시키는 것을 볼 수 있다. (JEDEC spec. ${\pm}5%$이내).

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.9-11
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• 2001

This paper deals with design and characteristic analysis of a permanent magnet linear synchronous motor for magnetic levitation stage of semi-conductor manufacture machine. In order to improve the control performance by detent force minimization, skew and PM offset method are used.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.364-368
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• 1999

We investigate the evaluation items of LSU (Laser Scanning Unit), such as beam size, f$\theta$ characteristics, linearity, skew and bow, optical power ratio between image height of 0mm and $\pm$108 mm, pitch error, Jitter and shift of printing position. Through the measurement of LSU using BSH (Beam Scan Head) installed on LMC (Linear Motion Controller) which moves linearly within the whole scanning range (-108 mm~+108 mm), we can ascertain plastic f$\theta$ lenses, which are manufactured by TVLP (Two-step Variable Low Pressure) molding method, to satisfy 600DPI(Dots Per Inch) performance.