• 제목/요약/키워드: Continuum Mechanism

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스프링 구조를 이용한 4자유도 연속체 로봇의 개발 (Development of a 4-DOF Continuum Robot Using a Spring Backbone)

  • 윤현수;이병주
    • 로봇학회논문지
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    • 제3권4호
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    • pp.323-330
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    • 2008
  • This work deals with a 4-DOF flexible continuum robot that employs a spring as its backbone. The mechanism consists of two modules and each module has 2 DOF. The special features of the proposed mechanism are the flexibility and the backdrivability of the whole body by using a spring backbone. Thus, even in the case of collision with human body, this device can ensure safety. The design and the kinematics for this continuum mechanism are introduced. The performance of this continuum mechanism was shown through simulation and experiment.

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수동 조작 내시경 수술 도구를 위한 힘이 증가된 연속체 메커니즘 및 이의 최적 형상 설계 (Continuum Mechanism with increased force and Optimal Design Method for Manually Controlled Endoscopic Surgical Instrument)

  • 이호열;정의성;정유수;박영상;송찬호;손재범
    • 로봇학회논문지
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    • 제16권2호
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    • pp.164-171
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    • 2021
  • This paper proposes a continuum mechanism for manually controlled endoscopic surgical instruments. The wire-driven mechanism is typically adapted for endoscopic surgical tools because motors cannot be embedded to the joints due to the size limitation. However, the conventional wire-driven mechanism has inherent problems caused by redundancy, such as deflection and low precision. It does not have operating force and manipulability for surgery. Therefore, a method to increase the force of the continuum mechanism using a multi-wire with simple mechanical structure is proposed. Moreover, for intuitive operation, a hand-controller mechanism that can manipulate the length of the wire without complex process is proposed. Finally, we show that the proposed mechanism and methods are applicable to endoscopic surgical tools through simple experiments.

손상역학을 이용한 섬유강화 복합재료의 피로해석 (Fatigue Analysis of Fiber-Reinforced Composites Using Damage Mechanics)

  • 임동민;윤인수;강기원;김정규
    • 대한기계학회논문집A
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    • 제30권2호
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    • pp.112-119
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    • 2006
  • Due to their intrinsic anisotropy, composite materials show quite complicated damage mechanism with their fiber orientation and stacking sequence and especially, their fatigue damage process is sequential occurrence of matrix cracking, delamination and fiber breakage. In the study, to propose new model capable of describing damage mechanism under fatigue loading, fatigue analysis of composite laminates based on damage mechanics, are performed. The average stress is disassembled with stress components of matrix, fiber and interlaminar interface through stress analysis. Each stress components are used to assess static damage analysis based on continuum damage mechanics (C.D.M.). Fatigue damage curves are obtained from hysteresis loop and assessed by the fatigue damage analysis. Then, static and fatigue damage analysis are combined. Expected results such as stress-cycle relation are verified by the experimental results of fatigue tests.

Failure analysis of laminates by implementation of continuum damage mechanics in layer-wise finite element theory

  • Mohammadi, B.;Hosseini-Toudeshky, H.;Sadr-Lahidjani, M.H.
    • Structural Engineering and Mechanics
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    • 제33권6호
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    • pp.657-674
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    • 2009
  • In this paper a 3-D continuum damage mechanics formulation for composite laminates and its implementation into a finite element model that is based on the layer-wise laminate plate theory are described. In the damage formulation, each composite ply is treated as a homogeneous orthotropic material exhibiting orthotropic damage in the form of distributed microscopic cracks that are normal to the three principal material directions. The progressive damage of different angle ply composite laminates under quasi-static loading that exhibit the free edge effects are investigated. The effects of various numerical modeling parameters on the progressive damage response are investigated. It will be shown that the dominant damage mechanism in the lay-ups of [+30/-30]s and [+45/-45]s is matrix cracking. However, the lay-up of [+15/-15] may be delaminated in the vicinity of the edges and at $+{\theta}/-{\theta}$ layers interfaces.

Finite element modeling of concentric-tube continuum robots

  • Baek, Changyeob;Yoon, Kyungho;Kim, Do-Nyun
    • Structural Engineering and Mechanics
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    • 제57권5호
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    • pp.809-821
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    • 2016
  • Concentric-tube continuum robots have formed an active field of research in robotics because of their manipulative exquisiteness essential to facilitate delicate surgical procedures. A set of concentric tubes with designed initial curvatures comprises a robot whose workspace can be controlled by relative translations and rotations of the tubes. Kinematic models have been widely used to predict the movement of the robot, but they are incapable of describing its time-dependent hysteretic behaviors accurately particularly when snapping occurs. To overcome this limitation, here we present a finite element modeling approach to investigating the dynamics of concentric-tube continuum robots. In our model, each tube is discretized using MITC shell elements and its transient responses are computed implicitly using the Bathe time integration method. Inter-tube contacts, the key actuation mechanism of this robot, are modeled using the constraint function method with contact damping to capture the hysteresis in robot trajectories. Performance of the proposed method is demonstrated by analyzing three specifications of two-tube robots including the one exhibiting snapping phenomena while the method can be applied to multiple-tube robots as well.

Characteristics of failure surfaces induced by embankments on soft ground

  • Hong, Eun-Soo;Song, Ki-Il;Yoon, Yeo-Won;Hu, Jong-Wan
    • Geomechanics and Engineering
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    • 제6권1호
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    • pp.17-31
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    • 2014
  • This paper investigates the development of failure surfaces induced by an embankment on soft marine clay deposits and the characteristics of such surfaces through numerical simulations and its comparative study with monitoring results. It is well known that the factor of safety of embankment slopes is closely related to the vertical loading, including the height of the embankment. That is, an increase in the embankment height reduces the factor of safety. However, few studies have examined the relationship between the lateral movement of soft soil beneath the embankment and the factor of safety. In addition, no study has investigated the distribution of the pore pressure coefficient B value along the failure surface. This paper conducts a continuum analysis using finite difference methods to characterize the development of failure surfaces during embankment construction on soft marine clay deposits. The results of the continuum analysis for failure surfaces, stress, displacement, and the factor of safety can be used for the management of embankment construction. In failure mechanism, it has been validated that a large shear displacement causes change of stress and pore pressure along the failure surface. In addition, the pore pressure coefficient B value decreases along the failure surface as the embankment height increases. This means that the rate of change in stress is higher than that in pore pressure.

컴플라이언트 메커니즘 설계를 위한 바닥 보 구조 기반 조인트 강성 조절법 (Ground Beam Structure Based Joint Stiffness Controlling Method for Compliant Mechanisms)

  • 장강원;김윤영;김명진
    • 대한기계학회논문집A
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    • 제30권10호
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    • pp.1187-1193
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    • 2006
  • Traditionally, the continuum-based topology optimization methods employing the SIMP technique have been used to design compliant mechanisms. Although they have been successful, the optimized mechanisms by the methods are usually difficult to manufacture because of their geometrical complexities. The objective of this study is to develop a topology optimization method that can produce easy-to-fabricate mechanism structure. The proposed method is a ground beam method where beam connectivity is controlled by the beam joint stiffness. In this approach, beam joint stiffness determines the mechanism configuration. Because b the ground structure beams have uniform thicknesses varying only discretely, the resulting mechanism topologies become easily manufacturable.

Growth features and nucleation mechanism of Ga1-x-yInxAlyN material system on GaN substrate

  • Simonyan, Arpine K.;Gambaryan, Karen M.;Aroutiounian, Vladimir M.
    • Advances in nano research
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    • 제5권4호
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    • pp.303-311
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    • 2017
  • The continuum elasticity model is applied to investigate quantitatively the growth features and nucleation mechanism of quantum dots, nanopits, and joint QDs-nanopits structures in GaInAlN quasyternary systems. We have shown that for GaInAlN material system at the critical strain of ${\varepsilon}^*=0.039$ the sign of critical energy and volume is changed. We assume that at ${\varepsilon}={\varepsilon}^*$ the mechanism of the nucleation is changed from the growth of quantum dots to the nucleation of nanopits. Obviously, at small misfit (${\varepsilon}$ < ${\varepsilon}^*$), the bulk nucleation mechanism dominates. However, at ${\varepsilon}$ > ${\varepsilon}^*$, when the energy barrier becomes negative as well as a larger misfit provides a low-barrier path for the formation of dislocations, the nucleation of pits becomes energetically preferable. The free energy of mixing for $Ga_{1-x-y}In_xAl_yN$ quasiternary system was calculated and studied and its 3D sketch was plotted.

Simultaneous observations of the H2O and SiO masers toward the late-type stars using KVN

  • Yun, Youngjoo;Cho, Se-Hyung;Kim, Jaeheon;Choi, Yoon Kyung
    • 천문학회보
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    • 제40권1호
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    • pp.59.2-59.2
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    • 2015
  • We present the results of simultaneous observations of the H2O and SiO masers emitted from the circumstellar envelopes of the late-type stars. These observations have been carried out at the K and Q bands using KVN since 2014 August and were scheduled to test the feasibility of multi-frequency phase referencing analysis on the maser lines. In order to increase the accuracy of group delay solution in the fringe search on the continuum source, the IF channels were randomly distributed within the available bandwidth of 500 MHz in each band. The positions of all maser spots are relatively described with respect to the position of the reference continuum source through the source frequency phase referencing technique, and this provides the astrometric position accuracy. Therefore, the relative locations of the H2O maser spots with respect to the SiO maser spots are determined from our observations, and the capability of the simultaneous multi-band observation of KVN is proved to be powerful to study the maser pumping mechanism around the late-type stars.

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An advanced single-particle model for C3S hydration - validating the statistical independence of model parameters

  • Biernacki, Joseph J.;Gottapu, Manohar
    • Computers and Concrete
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    • 제15권6호
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    • pp.989-999
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    • 2015
  • An advanced continuum-based multi-physical single particle model was recently introduce for the hydration of tricalcium silicate ($C_3S$). In this model, the dissolution and the precipitation events are modeled as two different yet simultaneous chemical reactions. Product precipitation involves a nucleation and growth mechanism wherein nucleation is assumed to happen only at the surface of the unreacted core and product growth is characterized via a two-step densification mechanism having rapid growth of a low density initial product followed by slow densification. Although this modeling strategy has been shown to nicely mimic all stages of $C_3S$ hydration - dissolution, dormancy (induction), the onset of rapid hydration, the transition to slow hydration and prolonged reaction - the major criticism is that many adjustable parameters are required. If formulated correctly, however, the model parameters are shown here to be statistically independent and significant.