• 제목/요약/키워드: Reference Point

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배관에 존재하는 원주방향 표면균열에 대한 파괴거동 해석 (ll) - 유한요소해석을 통한 검증 - (Fracture Behavior Estimation for Circumferential Surface Cracked Pipes (ll) - Finite Element Validation -)

  • 김진수;김윤재;김영진
    • 대한기계학회논문집A
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    • 제26권1호
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    • pp.139-146
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    • 2002
  • This paper provides validations of the reference stress based J and $C^{*}$ estimations, proposed in Part I, for inner, circumferential surface cracked pipes under internal pressure and global bending against detailed 3-D elastic-plastic and elastic-creep FE results. For this purpose, actual tensile properties of two typical stainless steels (TP304 and TP316) are used for elastic-plastic FE analyses and two realistic creep laws are used for elastic-creep FE analyses. For a total of twenty cases considered in this paper, agreements between the proposed reference stress based J and $C^{*}$ estimations and the FE results are excellent. More important aspect of the proposed estimations is that they can be used to estimate J and $C^{*}$ not only at the deepest point of the surface crack but also at an arbitrary point along the crack front.front.

배관 원주방향 표면균열에 대한 탄소성 파괴 파라미터의 예측 (II) (Engineering Estimation of Elastic-Plastic Fracture Parameter for Circumferential Surface Cracked Pipes: Part II)

  • 김윤재;김진수;김영진;박윤원
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2001년도 춘계학술대회논문집A
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    • pp.310-315
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    • 2001
  • This paper provides validations of the reference stress based J and $C^*$ estimations, proposed in Part I, for inner, circumferential surface cracked pipes under internal pressure and global bending against detailed 3-D elastic-plastic and elastic-creep FE results. For this purpose, actual tensile properties of two typical stainless steels (TP304 and TP316) are used for elastic-plastic FE analyses and two realistic creep laws are used for elastic-creep FE analyses. For a total of twenty cases considered in this paper, agreements between the proposed reference stress based J and $C^*$ estimations and the FE results are excellent. More important aspect of the proposed estimations is that they can be used to estimate J and $C^*$ not only at the deepest point of the surface crack but also at an arbitrary point along the crack front.

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목표 ZMP 궤적 기반 휴머노이드 로봇 이족보행의 최적 관절궤적 생성 (Optimal Joint Trajectory Generation for Biped Walking of Humanoid Robot based on Reference ZMP Trajectory)

  • 최낙윤;최영림;김종욱
    • 로봇학회논문지
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    • 제8권2호
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    • pp.92-103
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    • 2013
  • Humanoid robot is the most intimate robot platform suitable for human interaction and services. Biped walking is its basic locomotion method, which is performed with combination of joint actuator's rotations in the lower extremity. The present work employs humanoid robot simulator and numerical optimization method to generate optimal joint trajectories for biped walking. The simulator is developed with Matlab based on the robot structure constructed with the Denavit-Hartenberg (DH) convention. Particle swarm optimization method minimizes the cost function for biped walking associated with performance index such as altitude trajectory of clearance foot and stability index concerning zero moment point (ZMP) trajectory. In this paper, instead of checking whether ZMP's position is inside the stable region or not, reference ZMP trajectory is approximately configured with feature points by which piece-wise linear trajectory can be drawn, and difference of reference ZMP and actual one at each sampling time is added to the cost function. The optimized joint trajectories realize three phases of stable gait including initial, periodic, and final steps. For validation of the proposed approach, a small-sized humanoid robot named DARwIn-OP is commanded to walk with the optimized joint trajectories, and the walking result is successful.

Validation of three-dimensional digital model superimpositions based on palatal structures in patients with maximum anterior tooth retraction following premolar extraction

  • Liu, Jing;Koh, Kyong-Min;Choi, Sung-Hwan;Kim, Ji-Hoi;Cha, Jung-Yul
    • 대한치과교정학회지
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    • 제52권4호
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    • pp.258-267
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    • 2022
  • Objective: This study aimed to evaluate the superimposition accuracy of digital modes for measuring tooth movement in patients requiring anterior retraction after premolar extraction based on the proposed reference regions. Methods: Forty patients treated with bilateral maxillary first premolar extraction were divided into two groups: moderate retraction (< 7.0 mm) and maximum retraction (≥ 7.0 mm). Central incisor displacement was measured using cephalometric superimpositions and three-dimensional (3D) digital superimpositions with the 3rd or 4th ruga as the reference point. The Wilcoxon signed-rank test and linear regression analyses were performed to test the significance of the differences and relationships between the two measurement techniques. Results: In the moderate retraction group, the central incisor anteroposterior displacement values did not differ significantly between 3D digital and cephalometric superimpositions. However, in the maximum-retraction group, significant differences were observed between the anteroposterior displacement evaluated by the 3rd ruga superimposition and cephalometric methods (p < 0.05). Conclusions: This study demonstrated that 3D digital superimpositions were clinically as reliable as cephalometric superimpositions in assessing tooth movements in patients requiring moderate retraction. However, the reference point should be carefully examined in patients who require maximum retraction.

SRR과 DRR을 이용한 멀티미디어 문서 그룹화 (Grouping of Multimedia Documents using SRR and DRR)

  • 이종득;김양범;정택원
    • 한국컴퓨터산업학회논문지
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    • 제2권4호
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    • pp.435-442
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    • 2001
  • 최근에 인터넷상에서 정보이용이 급증함에 따라 멀티미디어 정보를 효율적으로 관리하고 검색하기 위한 여러 가지 방법들이 제안되고 있다. 따라서 본 논문에서는 SRR(Semantic Reference Relation)과 DRR(Direct Reference Relation)을 이용한 새로운 그룹화 방법을 제안한다. 제안된 방법은 MDI(Multimedia Document Informations)를 멀티미디어 객체 클러스터로 간주하여 그룹화 한다. 제안된 방법의 성능을 알아보기 위하여 1000개의 멀티미디어 문서데이터를 테스트하며, 그 결과 제안된 방법의 성능이 보다 효율적임을 보인다.

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기준모델 추종 자구구성 퍼지 논리 제어기 (Reference Model Following Self-Organizing Fuzzy Logic Controller)

  • 배상욱;권춘기;박귀태
    • 한국지능시스템학회논문지
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    • 제4권1호
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    • pp.24-34
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    • 1994
  • A RMFSOC(Reference Model Following Self-Organizing Fuzzy Logic Controller) is propose in this paper. In the RMFSOC, the refernce model is introduced, where the desired control performance can be specified by an operator of the controlled process. The self-organizing level of the RMFSOC organizes the control rules of FLC which make the process output follow the reference model output. In addition, for the use of preventing improper modifications of control rules, a complementary decission rule is induced from the possible relations between the process output and reference model output. Through a simulation study, it is shown that the robustness of the control system using the proposed RMFSOC to the set-point changes and distur bances can be greatly improved being conpared with that of the control system using the Procyk and Mamdani's SOC.

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레퍼런스 흐름에 기반한 디자인 패턴의 확장 지점 식별 (Identification of the Extension Points of Design Patterns Based on Reference Flows)

  • 김희천;박찬진;김택수;유찬우;이형원
    • 정보처리학회논문지D
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    • 제19D권4호
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    • pp.293-298
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    • 2012
  • 디자인 패턴은 기존 소프트웨어의 설계 정보를 추상화하는 단위로 사용될 수 있다. 소프트웨어의 기능을 확장하기 위해 설계를 파악하고자 할 때 디자인 패턴의 인스턴스를 파악하는 것 만으로는 충분치 않을 수 있는데, 이는 기능의 확장이 일어나는 지점이 패턴 인스턴스 바깥에 존재할 수 있기 때문이다. 본 논문에서는 디자인 패턴의 핵심적인 구조를 구성하는 과정으로서 레퍼런스 흐름을 정의하였으며, 레퍼런스 흐름을 이용하여 패턴의 확장 지점을 찾아내는 방법을 제시하였다.

다른 선폭들로 구성된 격자형 교정판을 이용한 간단한 카메라 교정 시스템의 개발 (A development of the simple camera calibration system using the grid type frame with different line widths)

  • 정준익;최성구;노도환
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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    • pp.371-374
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    • 1997
  • Recently, the development of computer achieves a system which is similar to the mechanics of human visual system. The 3-dimensional measurement using monocular vision system must be achieved a camera calibration. So far, the camera calibration technique required reference target in a scene. But, these methods are inefficient because they have many calculation procedures and difficulties in analysis. Therefore, this paper proposes a native method that without reference target in a scene. We use the grid type frame with different line widths. This method uses vanishing point concept that possess a rotation parameter of the camera and perspective ration that perspect each line widths into a image. We confirmed accuracy of calibration parameter estimation through experiment on the algorithm with a grid paper with different line widths.

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An Improved Guidance Algorithm for Smooth Transition at Way-Points in 3D Space for Autonomous Underwater Vehicles

  • Subramanian, Saravanakumar;Thondiyath, Asokan
    • International Journal of Ocean System Engineering
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    • 제2권3호
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    • pp.139-150
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    • 2012
  • This paper presents an improved guidance algorithm for autonomous underwater vehicles (AUV) in 3D space for generating smoother vehicle turn during the course change at the way-points. The way-point guidance by the line-of-sight (LOS) method has been modified for correcting the reference angles to achieve minimal calculation and smoother transition at the way-points. The algorithm has two phases in which the first phase brings the vehicle to converge to a distance threshold point on the line segment connecting the first two way-points and the next phase generates an angular path with smoother transition at the way-points. Then the desired angles are calculated from the reference and correction angles. The path points are regularly parameterized in the spherical coordinates and mapped to the Cartesian coordinates. The proposed algorithm is found to be simple and can be used for real time implementation. The details of the algorithm and simulation results are presented.

Surface Encoder Based on the Half-shaded Square Patterns (HSSP)

  • Lee, Sang-Heon;Jung, Kwang-Suk;Park, Eui-Sang;Shim, Ki-Bon
    • International Journal of Precision Engineering and Manufacturing
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    • 제9권3호
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    • pp.82-84
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    • 2008
  • A surface encoder based on the Half-shaded square pattern (HSSP) is presented. The HSSP working as reference grid is composed of the straight lines which are easy to be fabricated and make measuring time short. Since the periodic cell is separated in ON/OFF by the $45^{\circ}$ straight line, the duration from the starting point of scanning to the first rising edge and the duty cycle of the pulse train vary with respect to the position of the starting point. And the relationship between X and Y position and the duration, and duty cycle is described in the simple linear equation. Therefore, it is possible to measure X and Y position with the measured duration and duty cycle without calculating load. Through the test set-up, the feasibility of the proposed surface encoder was verified. Also the future works for improvement of performance were suggested.