• 한국산업융합학회 논문집
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• 제18권4호
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• pp.231-240
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• 2015

In this paper, it was presented to design and analyze the kinematics of grasping a rigid object by means of multi-degrees-of-freedom hand fingers. It is shown firstly that a set of kinematic equation describing dynamics system of the arm and object together with geometric constraint of tight area-contacts is formulated by Lagrange's equation. It has been presented secondly that the problems of controlling both the forces of pressing object and the rotation angle of the object under the geometric constraints are discussed. In this research, the control method for static stable grasping and enhancing dexterity in manipulating things is proposed. It is illustrated by computer simulation that the control system gives the performance improvement in the kinematic grasping of the hand fingers of robot.

• Advances in aircraft and spacecraft science
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• 제2권1호
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• pp.57-76
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• 2015

We investigated complex damped modes in beams in the presence of a viscoelastic layer sandwiched between two elastic layers. The problem was solved using two approaches, (1) Rayleigh beam theory and analyzed using the Ritz method, and (2) by using 2D plane stress elasticity based finite-element method. The damping in the layers was modeled using the complex modulus. Simply-supported, cantilever, and viscously supported boundary conditions were considered in this study. Simple trigonometric functions were used as admissible functions in the Ritz method. The key idea behind sandwich structure is to increase damping in a beam as affected by the presence of a highly-damped core layer vibrating mainly in shear. Different assumptions are utilized in the literature, to model shear deformation in the core layer. In this manuscript, we used FEM without any kinematic assumptions for the transverse shear in both the core and elastic layers. Moreover, numerical examples were studied, where the base and constraining layers were also damped. The loss factor was calculated by modal strain energy method, and by solving a complex eigenvalue problem. The efficiency of the modal strain energy method was tested for different loss factors in the core layer. Complex mode shapes of the beam were also examined in the study, and a comparison was made between viscoelastically and viscously damped structures. The numerical results were compared with those available in the literature, and the results were found to be satisfactory.

• 한국전자통신학회논문지
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• 제8권11호
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• pp.1665-1674
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• 2013

본 논문에서는 허리 관절을 갖는 4족 로봇의 효율적인 경사면 보행을 위해 유전 알고리듬(Genetic Algorithm: GA)을 이용한 경사면 보행 방법을 제안한다. 제안한 방법에서는 먼저, 허리 관절을 갖는 4족 로봇의 기구학적 모델을 유도하며, GA를 수행하기 위한 유전자 및 적합도 함수를 설정한다. 또한, 경사면에서 최적의 에너지 안정여유도(Energy Stability Margin: ESM)를 갖는 4족 로봇의 자세와 도달 영역 내의 발끝 착지 지점을 GA를 이용하여 자동으로 탐색하여 보행한다. 마지막으로, 4족 보행 로봇의 모의 실험을 통해 기존 방법과 비교함으로써 본 논문에서 제안한 방법의 효용성을 검증한다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.149-152
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• 1999

Computer-Aided Engineering (CAE) is one of the most effective method in design of golf clubs for determination of optimum shapes in short lead time. A new design of golf club drive with gas-filled titanium head has been carried out using two FEM softwares MARC and DYNA-3D. The main research work focuses on the decision of face thickness and the effect of filled gas pressure by analyzing the change of the kinematic energy of the ball during impact.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.392-395
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• 1995

This paper presents a time efficient method for determining a sequence of locations of a mobile manipulator that facilitates tracking of continuous path in cluttered environment. Given the task trajectory in the form of octree data structure, the algorithm performs characterization of task space and subsequent multistage optimization process to determine task feasible locations of the robot. Firstly, the collision free portion of the trajectory is determined and classified according to uniqueness domains of the inverse kinematics solutions. Then by implementing the extent of task feasible subspace into an optimization criteria, a multistage optimization problem is formulated to determines the task feasible locations of the mobile manipulator. The effectiveness of the proposed method is shown through a simulation study performed for a 3-d.o.f. manipulator with generic kinematic structure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.519-524
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• 2004

This study is concerned with the braking distance estimation using frictional energy rate. First, steady state rolling analysis is performed, and using this result, the braking distance is estimated. Dynamic rolling analysis during entire braking time period is impratical, so that this study divides the vehicle velocity by 10km/h to reduce the analysis time. The multiplication of the slip rate and the shear stress provides the frictional energy rate. Using frictional energy rate, total braking distance is estimated, In addition, ABS(Anti-lock Brake System) is considered, and two type of slip ratios are compared, One is 15% slip ratio for the ABS condition, and the other is 100% slip ratio which leads lo the almost same braking distance as the elementary kinematic theory. A slip ratio is controlled by angular velocity in ABAQUS/Explicit, A 15% slip ratio gives the real vehicle's braking distance when the frictional energy occurred al disk pad is included. Disk pad's frictional energy rate is calculated by the theoretical approach.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.967-972
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• 2008

This paper presents the free vibration analysis of a circular plate with a concentric square hole. The present problem deals with the numerical calculation of the natural frequencies and mode shapes of vibration of the structure by means of Independent Coordinate Coupling Method (ICCM). In this study, the boundary condition is the edge of the square hole is free and the outer circular plate is simply supported. Due to the geometric abnormality, this analysis does not permit an exact solution. Since the ICCM employs coordinate systems corresponding to each domain independently, the kinetic and potential energy expressions necessary for the Rayleigh-Ritz method can be easily obtained. Lastly, the kinematic relation is imposed. In this way, the eigenvalue problem can be easily set up. The numerical results show the efficacy of the ICCM and changes in natural frequencies and modes due to the square hole size.

• 한국태양에너지학회 논문집
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• 제36권3호
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• pp.9-16
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• 2016

This paper discusses a refined model for investigating the micro-mechanical behavior of beam-like structures, which are composed of various elastic moduli and complex geometries varying through the cross-section directions and are also periodically-repeated and heterogeneous along the axial direction. Following the previous work (Lee and Yu, 2011), the original three-dimensional static problem is first formulated in a unified and compact form using the concept of decomposition of the rotation tensor. Taking advantage of the smallness of the cross-sectional dimension-to-length parameter and the micro-to-macro heterogeneity, while also performing homogenization along the dimensional reduction simultaneously, the variational asymptotic method is rigorously used to construct a total energy function, which is asymptotically correct up to the second order. Furthermore, through the transformation procedure based on the pure kinematic relations and the linearized equilibrium equations, a generalized Timoshenko model is systematically established. For the purpose of dealing with realistic and complex geometries and constituent materials at the microscopic level, this present approach is incorporated into a commercial analysis package. A few examples available in literature are used to demonstrate the consistency and efficiency of this proposed model, especially for the structures, in which the effects of transverse shear deformations are significant.

• Structural Engineering and Mechanics
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• 제75권6호
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• pp.785-797
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• 2020

As the growth of world trade has surged rapidly over the past years, the number is expected to continue growing over the coming years. Although the transportation costs can be reduced by using larger vessels, however, new berthing structures have to be constructed in order to cater for the larger vessels. This leads to a need for researching on designing a better berthing structure. For optimization of berthing structure design, we need to provide a better estimation of berthing energy than the previous methods in the existing guidelines. In this study, several berthing parameters were collected from previous works and researches. Moreover, the scenarios were selected efficiently by using a sampling technique. First, the berthing energy was calculated by executing 150 numerical simulations. Then, the numerical simulation results were compared with the results calculated by existing methods quantitatively to investigate the sensitivity of the berthing parameters and the accuracy of existing methods. The numerical method results have shown some deviation with respect to the existing method results in which the degree of deviation varies with the methods and the tendency of differences is dependent on certain berthing parameters. Then, one of the existing methods which has shown a small deviation was selected as a representative method and applied with several safety factors to obtain a suitable safety factor for the design.

• 대한기계학회논문집A
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• 제37권1호
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• pp.55-60
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• 2013

컴파운더 보우는 리커브 보우와 비교하여 케이블 및 캠 풀리로 구성되는 지레시스템을 사용하여, 궁사가 보우를 최대 위치로 당기기 위해 필요로 하는 힘을 줄이는 동시에 더 많은 에너지를 축적할 수 있도록 해준다. 지금까지 컴파운더 보우의 효율 및 성능을 향상시키기 위해 경험적인 방법에 기초하여 많은 특허가 제안되었지만, 해석적인 방법에 대한 연구는 별로 없었다. 그러므로 본 연구에서는 컴파운더 보우 지레 시스템의 기구학적인 해석을 위한 방법을 제안하여 지레시스템의 캠 형상 및 보우 날개의 재질변화에 따른 효과를 설계자가 쉽게 예측할 수 있도록 하고자 한다.