• International Journal of Naval Architecture and Ocean Engineering
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• 제10권3호
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• pp.282-293
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• 2018

This paper attempts to address the motion parameter skip problem associated with three-dimensional trajectory tracking of an underactuated Autonomous Underwater Vehicle (AUV) using backstepping-based control, due to the unsmoothness of tracking trajectory. Through kinematics concepts, a three-dimensional dynamic velocity regulation controller is derived. This controller makes use of the surge and angular velocity errors with bio-inspired models and backstepping techniques. It overcomes the frequently occurring problem of parameter skip at inflection point existing in backstepping tracking control method and increases system robustness. Moreover, the proposed method can effectively avoid the singularity problem in backstepping control of virtual velocity error. The control system is proved to be uniformly ultimately bounded using Lyapunov stability theory. Simulation results illustrate the effectiveness and efficiency of the developed controller, which can realize accurate three-dimensional trajectory tracking for an underactuated AUV with constant external disturbances.

• 한국디지털건축인테리어학회논문집
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• 제11권2호
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• pp.61-70
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• 2011

This study aims to establish the concept about a new approaching method dor remodeling in the planning step. also, this study sets up the way how to approach in a dimensional way by classifying the conceptual composition of the target housing as a method. The dimensional definition is as below. The one dimensional approach: the spot. the two dimensional approach: the line, the three dimensional approach: the apatial mass, the four dimensional approach: space + time, the n dimensional (multi-dimensional) approach: the space + time + emotion. The research findings are as follows : For the purpose of remodeling, the old housing should be viewed in the three dimensional shape and space. It is defined as multi-dimensional module method to design the shape and space of the target housing in a multi-dimensional point, considering the three dimensional space composition, the emotion of the user, the housing itself. and the time of the user.

• 소성∙가공
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• 제21권4호
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• pp.252-257
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• 2012

Crystallographic texture evolution during forming processes has a significant effect on the anisotropic flow behavior of crystalline material. In this study, a crystal plasticity finite element method (CPFEM), which incorporates the crystal plasticity constitutive law into a three-dimensional finite element method, was used to investigate texture evolution of a face-centered-cubic material - an aluminum alloy. A rate-dependent polycrystalline theory was fully implemented within an in-house program, CAMPform3D. Each integration point in the element was considered to be a polycrystalline aggregate consisting of a large number of grains, and the deformation of each grain in the aggregate was assumed to be the same as the macroscopic deformation of the aggregate. The texture evolution during three different deformation modes - uniaxial tension, uniaxial compression, and plane strain compression - was investigated in terms of pole figures and compared to experimental data available in the literature.

• 대한기계학회논문집A
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• 제24권1호
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• pp.240-249
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• 2000

An improved global optimization algorithm is developed by extending the domain elimination method. The concept of triangular patch consists of two or more trajectories of local minimizations is introduced to widen the attraction region of the domain elimination method. Using the an-]c between each of three vertices of the patch and a design point, we measure the proximity, between the design point and the patch. With the Gram-Schimidt orthonormalization, this method can be extended to general n-dimensional problems. We code the original domain elimination algorithm and a patch-based algorithm. Then we compare the performance of two algorithms. Through the well-known example problems. the algorithm using patch is shown to be superior to the original domain elimination algorithm in view of computational efficiency.

• 한국지리정보학회지
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• 제23권4호
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• pp.16-41
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• 2020

실제 공간의 분포 또는 양적 속성을 대변하는 지리정보 입력은 지구시스템 모의 내에서 주요 관심사가 되고 있다. 많은 연구에서 다양한 격자 해상도에서의 지표면 특성에 대한 부정확한 추정이 모델링 결과를 크게 바꾸는 것으로 나타났다. 따라서, 이 논문은 도시지역 건물들의 분포와 면적·체적 속성을 반영하기 위해서, 항공라이다로 수집된 3DPC(three-dimensional point cloud) 샘플링 체계에 Monte Carlo Integration(MCI) 기법 기반 공간확률(spatial probability)을 적용을 제안하였다. 건물 식별과 관련해 공간확률(SP) 임계치, 격자 크기, 3차원점군 밀도 세 인자의 결정규칙 적용 결과가 비교되었다. 연구 결과, 건물의 격자가 커짐에 따라 식별되는 건물의 면적 속성이 증가하였다. 공간 모델링 및 분석의 신뢰성을 높이기 위해서는 샘플링 체계에서의 결정규칙을 사용하여 건물의 면적 속성을 조정하는 것이 권장된다. 제안된 방법은 모델링 분야가 요구하는 크고 작은 격자의 변화에서도 일정하게 건물 면적 속성이 유지되도록 지원할 것이다.

• 전기학회논문지
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• 제64권8호
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• pp.1231-1239
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• 2015

We developed a robot that has four limbs, each of which has the same kinematic structure and has 6 degrees of freedom. The robot is 600mm high and weighs 4.3kg. The robot can perform walking and manipulating task by using the four limbs selectively. The robot has three walking patterns. The first one is biped walking, which uses two rear limbs as legs and two front limbs as arms. The second one is biped walking with supporting arms, which is basically biped walking but uses two arms as supporting legs for increasing stability of the robot. The last one is quadruped walking, which uses all the four limbs as legs. When a task for the robot is given, the robot approaches the task point by selecting an appropriate walking pattern among three walking patterns and performs the task. The robot has many degrees of freedom and is a redundant system for a three dimensional task. We propose a redundancy resolution method, in which the robot’s translational move to the task point is modeled as a prismatic joint and optimal solutions are obtained by optimizing some performance criteria. Several simulations are performed for the validity of the proposed method.

• Corrosion Science and Technology
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• 제11권5호
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• pp.173-178
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• 2012

To manage the wall thinning of carbon steel piping in nuclear power plants, the utility of Korea has performed thickness inspection for some quantity of pipe components during refueling outages and determined whether repair or replacement after evaluating UT (Ultrasonic Test) data. When the existing UT data evaluation methods, such as Band, Blanket, PTP (Point to Point) Methods, are applied to a certain pipe component, unnecessary re-inspecting situations may be generated even though the component does not thinned. In those cases, economical loss caused by repeated inspection and problems of maintaining the pipe integrity followed by decreasing of newly inspected components may be generated. EPRI (Electric Power Research Institute) in USA has suggested several statistical methods, TPM (Total Point Method), LSS (Least Square Slope) Method, etc. to distinguish whether multiple inspecting components have thinned or not. This paper presents the analysis results for multiple inspecting components over three times based on both NAM (Near Area of Minimum) Method developed by KEPCO-E&C and the other methods suggested by EPRI.

• 디지털콘텐츠학회 논문지
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• 제8권1호
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• pp.85-91
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• 2007

본 논문에서는 포인트 샘플링을 이용한 음함수 곡면에서 나타나는 앨리어싱을 줄이기 위한 새로운 하이브리드 앤티앨리어싱 방법을 제안한다. 하이브리드 앤티앨리어싱 방법은 하나의 음함수 곡면에 대해 Z-버퍼에서 나타나는 픽셀 값들의 차이를 구하여 세가지 형태의 Z-버퍼를 각각 사용하는 방법이다. 차이의 수준을 정하여 차이가 심할 때는 멀티 Z-버퍼를 사용하고 차이가 중간 정도일 때는 더블 Z-버퍼를 사용하며 차이가 경미할 때는 원래의 Z-버퍼만을 사용하여 3차원 객체를 표현하는 방법이다. 기존에 앤티앨리어싱 효과를 높이기 위하여 전체적으로 멀티 Z-버퍼를 사용하였는데 사용되는 Z-버퍼의 개수를 줄이면서 멀티 Z-버퍼를 사용한 것과 비슷한 효과를 보이는 효율적인 방법이다.

• 한국측량학회지
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• 제23권2호
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• pp.211-217
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• 2005

경계를 설정하기 위한 일반적인 방법은 등거리원칙이다. 등거리원칙은 각각의 기준선 또는 기준점의 경계에서 일정한 거리까지를 경계로 정하는 방법이다. 오랜 동안 해양의 공평한 경계를 정의하기 위한 노력이 진행되어, 모든 나라들이 적용할 수 있는 대양의 사용규제에 대한 단일협정인 유엔해양법협약이 채택되었다. 그 내용은 결국 당사국 간의 "공평"을 대원칙으로 한다는 것이다. 본 연구에서는 이러한 경계를 설정하는데 있어서의 한${\cdot}$일 양국의 실질적인 경계획선 방법에 대해 분석${\cdot}$비교하였다. 이를 위해 먼저 경계획선 과정에서의 기본이자 핵심이라 할 수 있는 양국의 측지계산 알고리즘을 분석하여 비교하였다. 양국의 실질적인 경계획선 알고리즘을 비교하기 위해 여러 가지 테스트를 수행하였다. 이에 향후 해양경계획정에 대비하여 효과적인 해양경계획선 알고리즘인 Three-Point 알고리즘을 제안한다. 또한 일본의 해양경계획선 알고리즘과의 비교를 통하여, 향후 경계분쟁에 대비한 기술적인 능력을 확보한다.

• 전력전자학회논문지
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• 제23권5호
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• pp.336-344
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• 2018

This study proposes a new PWM method for leakage current reduction and neutral point (NP) current control in three-phase three-level converter employed in bipolar DC distribution systems. The proposed PWM method uses medium vectors only when there is no need to control the NP current. Thus, common mode voltages are held constant to realize zero leakage current. Some space vectors that produce low-frequency common mode voltages are employed to minimize leakage currents when the average NP current needs to be a positive or negative value. The proposed space vector PWM is implemented based on barycentric coordinate. The validity of the proposed PWM method is verified by simulations and experiments.