• Title/Summary/Keyword: Stable angle

Search Result 651, Processing Time 0.028 seconds

Research of Stable Grapsing in Field Robot (Field-Robot의 안정적 파지운동 제어에 관한 연구)

  • 박경택;심재군;한현용;양순용;이병룡
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 1997.10a
    • /
    • pp.492-495
    • /
    • 1997
  • This paper aims to derive a mathematical model of the dynamics of handling task in field robot which stable grasping and manipulates a rigid object with some dexterity. Firstly, a set of differential equation describing dynamics of the manipulators and object together with geometric constraints of tight area-contacts on motion of the overall system is analyzed and a method of computer simulation for overall system of differential-algebraic equations is presented. Thirdly, simulation results are shown and the effects of geometric constraints of contact-area are discussed. Finally, it is shown that even in the simplest case of dual single D.O.F. manipulators there exists a sensory feedback from sensing data of he rotational angle of the object to command inputs to joint actuators and this feedback connection from sensing to action eventually realizes secure grasping of the object, provided that he object is of rectangular shape and motion is confined to a horizontal

  • PDF

Fabrication of Stable Water/Oil Separation Filter Using Effect of Surface Wettability (표면 젖음성을 이용한 물/오일 분리막 제작)

  • Kim, Dohyeong;An, Taechang
    • Journal of Sensor Science and Technology
    • /
    • v.25 no.3
    • /
    • pp.213-217
    • /
    • 2016
  • The superhydrophobic and superoleophobic meshes surfaces have been used in various applications such as self-cleaning, anti-icing, gas exchange, oil-water separation, sound-wave penetrable anti-wetting structures, etc. In particular, there are many studies for oil-water separation with environmental issues. Because of high pressure and dynamic environment, oil-water separation filters must have stable surface properties as super-hydrophobicity and superoleophobicity. The oleophobicity of surface depends on the surface chemistry and roughness of the surface. The roughness of oleophobic surface enhances its static contact angle and stability. The multi-scale hierarchical structure provides a stable superhydrophobic state by maintaining a Cassie state. In this research, we fabricated a superoleophobic mesh with a multi-scale hierarchical structure to increase the pressure resistance and adjusted a size of the mesh hole.

Injury Prevention Strategies of Landing Motion of Jumping Front Kick to Apply Free Style Poomsae of Taekwondo (태권도 자유 품새에 적용하기 위한 뛰어 앞차기 착지 동작의 상해 예방 전략)

  • Ryu, Sihyun
    • Korean Journal of Applied Biomechanics
    • /
    • v.30 no.1
    • /
    • pp.37-49
    • /
    • 2020
  • Objective: The purpose of this study was to investigate the injury factors of Taekwondo jumping kick during landing phase according to the experience of injury and to suggest a stable landing movement applicable to free style Poomsae. Method: The participants were non-injury group (NG), n = 5, age: 20.5±0.9 years; height: 171.6±3.6 cm; body weight: 65.7±4.4 kg; career: 5.0±2.7 years. Injury group (IG), n = 9, age: 21.0±0.8 years; height: 170.9±4.6 cm; body weight: 67.1±7.0 kg; career: 8.6±5.0 years. The variables are impact force, loading rate, vertical stiffness, lower limb joint angle, stability, balance, and muscle activity in the landing phase. Results: NG was statistically larger than IG in the gluteus medius (p<.05). The impact force, loading rate and vertical stiffness decreased as the landing foot angle, the ROM of lower limb joint angle and COM displacement increased (p<.05). Conclusion: Based on the results, it means that the landing foot angle plays an important role in the impact reduction during landing phase. It is required the training to adjust the landing foot angle.

Stability Analysis of Toppling Failure in Rock Slopes (암반사면의 전도파괴에 대한 안정해석)

  • 이명재;이인모
    • Geotechnical Engineering
    • /
    • v.14 no.2
    • /
    • pp.55-66
    • /
    • 1998
  • The purpose of this paper is to formulate and apply the stability analysis of toppling failure by considering the variation of discontinuity characteristics, slope geometry, and loading conditions. The stability condition on toppling failure of rock slope is mainly iuluenced by the dip angle $\alpha_B$ and H/t ratio. In order to check toppling failures in design, the stability charts composed of dip angle $\alpha_B$ versus H/t ratio have been constructed in the paper. In general, smaller dip angle $\alpha_B$ and smaller dip angle $\alpha_B$ and smaller H/T ratio give safer condition. The suggested curves change rapidly at the chitical point around the sone, H/t=4~6. The stable zone in stability charles becomes smaller due to step angle $\data$.

  • PDF

A Simulation for the Natural Frequencies of Curved Pipes Containing Fluid Flow with Various Elbow Angles (시뮬레이션에 의한 유체 유동 파이프 계의 곡관부의 각도 변화에 따른 고유진동수 고찰)

  • 최명진;장승호
    • Journal of the Korea Society for Simulation
    • /
    • v.10 no.1
    • /
    • pp.63-65
    • /
    • 2001
  • To investigate the natural frequencies of curved piping systems with various elbow angles conveying flow fluid, a simulation is performed considering Initial tension due to the inside fluid. The system is analyzed by finite element method utilizing straight beam element. Elbow part is meshed using 4 elements, and the initial tension is considered by inserting equivalent terms into the stiffness matrix. Without considering the initial tension, the system becomes unstable, that is, the fundamental natural frequency approaches to zero value fast, as the flow velocity reaches critical value. With the initial tension terms, the system becomes stable where there is no abrupt decrease of the fundamental natural frequency. The change rate of the natural frequency with respect to the flow velocity reduces. As elbow angle increases, the system becomes stiffer, then around 150 degrees of the elbow angle the natural frequency has the largest value, the value decreases after the angle of the largest natural frequency. When angle is between 170 degrees and 179 degrees, the natural frequency is very sensitive. This means that small change of angle results in great change of natural frequency, which is expected to be utilized in the control of the natural frequency of the piping system conveying flow fluid.

  • PDF

Evolution of sandstone shear strength parameters and its mesoscopic mechanism

  • Shi, Hao;Zhang, Houquan;Song, Lei
    • Geomechanics and Engineering
    • /
    • v.20 no.1
    • /
    • pp.29-41
    • /
    • 2020
  • It is extremely important to obtain rock strength parameters for geological engineering. In this paper, the evolution of sandstone cohesion and internal friction angle with plastic shear strain was obtained by simulating the cyclic loading and unloading tests under different confining pressures using Particle Flow Code software. By which and combined with the micro-crack propagation process, the mesoscopic mechanism of parameter evolution was studied. The results show that with the increase of plastic shear strain, the sandstone cohesion decreases first and then tends to be stable, while the internal friction angle increases first, then decreases, and finally maintains unchanged. The evolution of sandstone shear strength parameters is closely related to the whole process of crack formation, propagation and coalescence. When the internal micro-cracks are less and distributed randomly and dispersedly, and the rock shear strength parameters (cohesion, internal friction angle) are considered to have not been fully mobilized. As the directional development of the internal micro-fractures as well as the gradual formation of macroscopic shear plane, the rock cohesion reduces continuously and the internal friction angle is in the rise stage. As the formation of the macroscopic shear plane, both the rock cohesion and internal friction angle continuously decrease to a certain residual level.

Cutting Characteristics on Rake Angle in Laser-Assisted Machining of Silicon Nitride (질화규소의 예열선삭가공시 경사각에 따른 절삭특성)

  • Shin, Dong-Sig;Lee, Jae-Hoon;Lim, Se-Hwan;Kim, Jong-Do;Lee, Su-Jin
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.26 no.4
    • /
    • pp.47-54
    • /
    • 2009
  • In the last few years, lasers have found new applications as tools for ceramic machining which is laser-assisted machining(LAM). LAM process for the machining of difficult-to-machine materials such as structural ceramics, has recently been studied on silicon nitride workpiece for a wide range of operating condition. However, there have been few studies on rake angle in LAM process. In this paper we analyzed difference of machinability between positive and negative rake angle in tools. We have obtained interesting results that we could eliminate chattering, lower specific cutting and cutting ratio in case of positive rake angle. The results suggest that positive rake angled tools can make more plastic deformation and stable cutting of silicon nitride in comparison with negative rake angled one.

Compressive Fracture Behaviors of Transversely Isotropic Jointed Rock Model with an Opening (공동을 포함하는 횡등방성 절리암반 모델의 압축 파괴거동)

  • SaGong, Myung;Kim, Se-Chul;Yoo, Jea-Ho;Park, Du-Hee;Lee, J.S.
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • 2009.03a
    • /
    • pp.58-63
    • /
    • 2009
  • Biaxial compression test was conducted on a transversely isotropic synthetic jointed rock model for the understanding of the fracture behaviors of a sedimentary or metamorphic rocks with well developed bedding or foliation in uni-direction. The joint angles employed for the model are 30, 45, and 60 degrees to the horizontal, and the synthetic rock mass was made of early strength cement. From the biaxial compression test, initiation propagation of tensile cracks at norm to the joint angle was found. The propagated tensile cracks eventually developed rock blocks, which was dislodged from the rock mass. Furthermore, the propagation process of the tensile cracks varies with joint angle: lower joint angle model shows more stable and progressive tensile crack propagation. The experiment results were validated from the simulation by using discrete element method PFC 2D. From the simulation, as has been observed from the test, a rock mass with lower joint angle produces wider damage region and rock block by tensile cracks. In addition, a rock model with lower joint angle shows a progressive tensile cracks generation around the opening from the investigation of the interacted tensile cracks.

  • PDF

Stability Analysis of Jointed Rock Slope by D.E.M (개별요소법에 의한 절리 암반 비탈면의 안정성 해석)

  • Park, Geun-Uck;Lim, Han-Uk
    • Journal of Industrial Technology
    • /
    • v.21 no.B
    • /
    • pp.51-58
    • /
    • 2001
  • The Distinct Element Method (DEM) was used to analyze the stability of jointed rock slope, of which dimension are about 200m(length), 60m(height), $55^{\circ}$ dip. The Barton-Bandis joint model was used, as a constitutive model. The parameters such as JRC and spatial distribution characteristics of discontinuities were acquired through field investigation. Three different cases such as $51^{\circ}$, $45^{\circ}$ and $38^{\circ}$ in angle of rock slope were analyzed to decide a stable slope. To keep the jointed rock slope safely, it is proposed to reduce the height of slope from 60m to 48m and to reduce the angle of the from $55^{\circ}$ to $38^{\circ}$ too.

  • PDF

Facile preparation of superhydrophobic thin films using non-aligned carbon nanotubes

  • Goh, Yee-Miin;Han, Kok Deng;Tan, Lling-Lling;Chai, Siang-Piao
    • Advances in nano research
    • /
    • v.2 no.4
    • /
    • pp.219-225
    • /
    • 2014
  • A simple preparation method on creating superhydrophobic surface using non-aligned carbon nanotubes (CNTs) was demonstrated. Superhydrophobic CNT thin films were prepared by doping a sonicated mixture of CNTs and chloroform onto a glass slide. Water contact angles of the CNT thin films were measured using a contact angle goniometer. The thin films were characterized using laser microscope and scanning electron microscope. Experimental results revealed that the highest average contact angle of $162{\pm}2^{\circ}$ was achieved when the films' thickness was $1.628{\mu}m$. The superhydrophobic surface was stable as the contact angle only receded from $162{\pm}2$ to $157{\pm}2^{\circ}$ after 10 min under normal atmospheric condition.