• Journal of Power Electronics
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• 제13권2호
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• pp.206-213
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• 2013

In this paper, an improved passive snubber is investigated in a single-phase single-stage full-bridge boost power factor correction (PFC) converter, by which the voltage spike across primary side of the power transformer can be suppressed and the absorbed energy can be transferred to the output side. When compared with the basic passive snubber, the two single-inductors are replaced by a coupled-inductor in the improved snubber. As a result, synchronous resonances in the snubber can be achieved, which can avoid the unbalance of the voltage and current in the snubber. The operational principle of the improved passive snubber is analyzed in detail based on a single-phase PFC converter, and the design considerations of both the snubber and the coupled-inductor are given. Finally, a laboratory-made prototype is built, and the experimental results verify the feasibility of the proposed method and the validity of the theoretical analysis and design method.

• Journal of Power Electronics
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• 제15권5호
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• pp.1409-1420
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• 2015

In this paper, an algorithm using two bi-quad filters to suppress the wide-band resonance for PMSM servo systems is proposed. This algorithm is based on the double bi-quad filters structure, so it is named, "double bi-quad filter." The conventional single bi-quad filter method cannot suppress unexpected mechanical terms, which may lead to oscillations on the load side. A double bi-quad filter structure, which can cancel the effects of compliant coupling and suppress wide-band resonance, is realized by inserting a virtual filter after the motor speed output. In practical implementation, the proposed control structure is composed of two bi-quad filters on both the forward and feedback paths of the speed control loop. Both of them collectively complete the wide-band resonance suppression, and the filter on the feedback path can solve the oscillation on the load side. Meanwhile, with this approach, in certain cases, the servo system can be more robust than with the single bi-quad filter method. A step by step design procedure is provided for the proposed algorithm. Finally, its advantages are verified by theoretical analysis and experimental results.

• 조명전기설비학회논문지
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• 제23권8호
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• pp.41-47
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• 2009

디지털 기술 기반의 차세대 변전시스템과 관련하여 프로세스 버스까지 확장된 변전자동화시스템 구현에 관한 연구가 국내외에서 활발히 진행 중에 있다. 특히 IEC 61850 국제 규격이 적용된 머징유닛(Merging Unit)은 프로세스 기반 변전자동화시스템의 핵심 구성요소로 그 관심이 매우 크다. 본 논문에서는 변전소의 CT와 VT를 통합 전압 전류의 값을 IEC 61850 기반의 디지털 값인 SV(Sampled Value)로 변환하여 보내는 머징유닛의 기능과 통신서비스에 대한 적합성 성능 검증에 대한 방안을 제시하고 머징유닛을 시험할 수 있는 시험시스템을 보여주고자 한다.

• 한국산학기술학회논문지
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• 제12권1호
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• pp.38-44
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• 2011

본 자원탐사의 중요성이 증대되고 있는 상황에서, 효과적인 자원탐사방법의 최적설계 및 탐사자동화가 중대 관심사가 되고 있다. 본 연구는 수치적인 모델링의 문제점을 해결하기 위하여, 현장의 환경을 하드웨어적으로 재현한 탐사환경 축소모형 로봇 시스템을 제안한다. 종래의 이동로봇 시스템을 개량하여 케이블카용 로봇시스템을 개발하였다. 본 시스템은 로봇의 자장 노이즈를 극소화시키고, 자장 그레디언트의 현장 측정 재현을 통하여 효과적인 설계지침을 제공한다. 또한 케이블카형 이동방법은 이용하여, 험지에서 탐사 자동화등에 활용될 수 있다.

• 정보처리학회논문지D
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• 제10D권2호
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• pp.293-300
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• 2003

인터넷의 급속한 성장과 웹 관련 기술이 더 복잡해지면서 웹 응용 소프트웨어의 품질과 신뢰성이 중요하게 되었다. 웹 기반 소프트웨어는 전 세계에 흩어져 있는 수많은 사용자들을 대상으로 한다는 면에서 품질과 시험 방법 또한 중요하다. 이 논문은 브라우저 객체를 이용하여 HTML 웹 페이지의 사용자 입력 부분에 대한 테스트 케이스를 자동적으로 실행할 수 있는 방안을 제시하고 Javascript로 매핑하여 자동화가 가능함을 보였다. 스크립트 작성기를 만들면 Javascript를 작성하는 오버헤드를 줄일 수도 있다. 작성된 테스트 스크립트는 웹 기반 소프트웨어의 리그레션 테스트에 반복적으로 사용할 수 있다.

• Journal of Mechanical Science and Technology
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• 제14권7호
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• pp.752-763
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• 2000

The stress field around the dynamically propagating interface crack tip under a remote mixed mode loading condition has been studied with the aid of dynamic photoelastic method. The variation of stress field around the dynamic interface crack tip is photographed by using the Cranz-Shardin type camera having $10^6$ fps rate. The dynamically propagating crack velocities and the shapes of isochromatic fringe loops are characterized for varying mixed load conditions in double cantilever beam (DCB) specimens. The dynamic interface crack tip complex stress intensity factors, $K_1\;and\;K_2$, determined by a hybrid-experimental method are found to increase as the load mixture ratio of y/x (vertical/horizontal) values. Furthermore, it is found that the dynamically propagating interface crack velocities are highly dependent upon the varying mixed mode loading conditions and that the velocities are significantly small compared to those under the mode I impact loading conditions obtained by Shukla (Singh & Shukla, 1996a, b) and Rosakis (Rosakis et al., 1998) in the USA.

• 한국생산제조학회지
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• 제26권2호
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• pp.230-237
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• 2017

Various drones have extended application area very fast. In this paper, we define two contradictions in designing a portable-size drone by using TRIZ technique. The first is a physical contradiction between high rigidity and good portability, and the second is a technical contradiction between high stability and good portability. Through TRIZ technique, six design principles, which guide direction for optimal design, were driven. Consequently, an umbrella mechanism and design criteria were proposed for a portable-size drone. Detail design is verified through finite element method. Test results for the portable-size prototype drone show good performance, and prove its usefulness to be equivalent to a general full-size drone.

• Journal of Magnetics
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• 제21권1호
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• pp.65-71
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• 2016

To increase the retaining force, a novel design for a concentric, bi-directional, electromagnetic valve actuator that contains double-layer permanent magnets is presented in this paper. To analyze the retaining-force change caused by the magnets, an equivalent magnetic circuit (EMC) model is established, while the EMC circuit of a double-layer permanent-magnet valve actuator (DLMVA) is also designed. Based on a 3D finite element method (FEM), the calculation model is built for the optimization of the key DLMVA parameters, and the valve-actuator optimization results are adopted for the improvement of the DLMVA design. A prototype actuator is manufactured, and the corresponding test results show that the actuator satisfies the requirements of a high retaining force under a volume limitation; furthermore, the design of the permanent magnets in the DLMVA allow for the attainment of both a high initial output force and a retaining force of more than 100 N.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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• pp.70-77
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• 1996

Recently many efforts have been made to improve the efficiency of design and production of the structures using the automation system. But, this work has been progressed as independent or partial system. And, the study on the integrated system is not sufficient in application for practical problems yet. This paper deals with the fundamental concept of modeling system and application method on structural modeling. At first, the core of the integrated system is a shape modeling system that can represent the geometric and topological information. This system must be designed as an open system to be combined with each independent automation system. The appropriate concept to realize this system on structural modeling is object oriented modeling and this enables to integrate each automation system successfully, This concept was applied to automatic mesh generation. For shape modeling system, half-edge data structure that is being used in solid modeling was modified to handle the plate structure in the plane. And, to generate the triangular meshes, direct node connection method was used. And, as a result, the integrated system that generate the meshes of two dimensional structure automatically was realized. And, programmed by C++, these systems can be combined with other systems easily and have good reusability.

• Journal of Information Processing Systems
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• 제14권1호
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• pp.176-190
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• 2018

This paper presents a novel convolutional neural network based multi-feature fusion learning method for non-rigid 3D model retrieval, which can investigate the useful discriminative information of the heat kernel signature (HKS) descriptor and the wave kernel signature (WKS) descriptor. At first, we compute the 2D shape distributions of the two kinds of descriptors to represent the 3D model and use them as the input to the networks. Then we construct two convolutional neural networks for the HKS distribution and the WKS distribution separately, and use the multi-feature fusion layer to connect them. The fusion layer not only can exploit more discriminative characteristics of the two descriptors, but also can complement the correlated information between the two kinds of descriptors. Furthermore, to further improve the performance of the description ability, the cross-connected layer is built to combine the low-level features with high-level features. Extensive experiments have validated the effectiveness of the designed multi-feature fusion learning method.