• Structural Engineering and Mechanics
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• 제43권4호
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• pp.439-448
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• 2012

This paper investigates the load sharing of double circular arc helical gears considering the influence of assembly errors. Based on a load sharing formulae, a three-dimensional finite element tooth contact analysis (TCA) is implemented with commercial software package ANSYS. The finite element grid for the double circular arc gear contact model is automatically generated by using the APDL (ANSYS Parameter Design Language) embedded in ANSYS. The realistic rotation of gears is achieved by using a coupling degree-of-freedom method. Numerical simulations are carried out to exemplify the proposed approach. The distribution of contact stress and bending stress under specific loading conditions are computed and compared with those obtained from Hertz contact theory and empirical formulae to demonstrate the efficiency of the proposed load sharing calculation formulae and TCA approach.

• Bulletin of the Korean Chemical Society
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• 제28권10호
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• pp.1697-1704
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• 2007

We present results for transport properties of diatomic fluids by isothermal-isobaric (NpT) equilibrium molecular dynamics (EMD) simulations using Green-Kubo and Einstein formulas. As the molecular elongation of diatomic molecules increases from the spherical monatomic molecule, the diffusion coefficient increases, indicating that longish shape molecules diffuse more than spherical molecules, and the rotational diffusion coefficients are almost the same in the statistical error since random rotation decreases. The calculated translational viscosity decreases with the molecular elongation of diatomic molecule within statistical error bar, while the rotational viscosity increases. The total thermal conductivity decreases as the molecular elongation increases. This result of thermal conductivity for diatomic molecules by EMD simulations is again inconsistent with the earlier results of those by non-equilibrium molecular dynamics (NEMD) simulations even though the missing terms related to rotational degree of freedom into the Green-Kubo and Einstein formulas with regard to the calculation of thermal conductivity for molecular fluids are included.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1131-1135
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• 2004

In the virtual environment, force feedback to the human operator makes virtual experiences more realistic. However, the force feedback using active actuators such as motors can make the system active and sometimes unstable. To ensure the safe operation and enhance the haptic feeling, stability should be guaranteed. Both motors and brakes are commonly used for haptic device. A brake can generate a torque only against its rotation, but it is intrinsically stable. Consequently, motors and brakes are complementing each other. In this research, a two degree-of-freedom (DOF) haptic device equipped with both motors and brakes has been developed to provide better haptic effects. Each DOF is actuated by a pair of motor and brake. Modeling of the environment and the control method are needed to utilize both actuators. For various haptic effects, contact with the virtual wall and representation of friction effect are extensively investigated in this paper. It is shown that the hybrid haptic system is more suited to some applications than the motor-based active haptic system.

• 대한토목학회논문집
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• 제11권2호
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• pp.1-14
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• 1991

평면내에서의 비틀림에 대한 강성도를 갖는 3절점 삼각형 shell요소를 사용하여 박판으로 이루어진 곡석 또는 직선부재의 선형 탄성좌굴 해석을 위한 컴퓨터 프로그램을 개발 하였다. 판의 좌굴 해석과 보의 횡 비틈 좌굴해석을 통하여 본 프로그램의 타당성을 입증하였고, 이를 순수 휨을 받는 양단의 단순지지된 원호 아치의 좌굴해석에 적용시켜 그 결과들을 다른 연구 결과들과 비교 검토하여 보았다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.250-252
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• 2007

In this paper presents a control algorism for myoelectric hand prosthesis(MHP) with 2 degree of freedom(DOF), which consists of a mechanical hand, a surface myoelectric sensor(SMES) for measuring myoelectric signal, a control system and a charging battery. The actuation for the 2-DOF hand functions such as grasping and wrist rotation was performed by two DC-motors, and controlled by myoelectric signal measured from the residual forearm muscle. The two controllers were made of a RISC-type microprocessor, and its software was executed on a real-time kernel. The experimental results were showed that the proposed a control algorism is feasible for the MHP.

• 대한방사선치료학회지
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• 제29권2호
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• pp.53-64
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• 2017

목 적: 표적의 길이가 긴(length) 환자의 용적회전변조 방사선치료(V-MAT) 시 회전방향 오차의 크기에 따른 선량차이 경향을 $HexaPOD^{TM}$ evo RT system(6DoF couch)을 통해 알아보고 그 유용성을 평가하고자 하며, 이에 따른 회전오차 보정의 필요성을 제안하고자 한다. 대상 및 방법: 본원에서 치료를 받은 Esophagus cancer와 SCL을 포함한 Breast cancer 환자 중 HexaPOD 6DoF(Six-Degree of Freedom) couch를 사용한 10명을 대상으로 하였다. 6DoF couch를 이용하여 Rx(pitch), Ry(roll), Rz(yaw) 방향의 회전오차의 적용여부에 따른 선량차이를 알아보기 위하여 x, y, z축에 대한 자세오차를 확인하고, 자세 회전오차 값을 6DoF couch에 부여 임의의 오차를 발생시켜 변형된 선량계측 품질보증(Delivery Quality Assurance, DQA)을 시행, 점 선량과 감마값을 비교 분석하였다. 추가적으로 3cm의 직경에 5, 10, 15, 20 cm의 길이를 가진 각각의 표적의 치료계획에 회전오차의 크기를 $1^{\circ}$ 간격으로 적용한 후, 표적의 길이와 회전오차의 종류 및 크기에 따른 감마통과율의 변화양상을 확인했다. 결 과: 자세 회전오차가 적용된 경우의 점 선량과 감마통과율의 평균오차는 각각 Rx 방향에서 $2.50{\pm}1.11%$, $84.1{\pm}7.39%$, Ry 방향에서 $2.36{\pm}1.16%$, $81.0{\pm}8.49%$, Rz 방향에서 $2.35{\pm}1.10%$, $84.4{\pm}6.99%$를 나타냈다. 또한, 표적의 길이와 회전오차의 종류 및 크기에 따른 감마통과율 분석 결과 Ry 방향을 제외한 Rx와 Rz 방향에서 회전오차가 커질수록 감마통과율은 전반적으로 감소하는 경향을 보였으며, 특히 10 cm의 표적, Rz 방향으로 $2.5^{\circ}$ 회전오차가 부여된 경우에서 가장 낮은 감마통과율인 74.2 %를 나타냈다. 결 론: 표적의 길이가 긴 치료부위의 용적회전변조 방사선치료 시 회전오차의 보정은 필요하며, 6DoF couch의 사용은 환자자세의 재현성과 치료의 질적 효율을 높일 것으로 사료된다.

• 한국인터넷방송통신학회논문지
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• 제19권6호
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• pp.109-116
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• 2019

본 논문은 얼굴 형상 인식을 위한 보다 안정적이며 조명 변화와 회전에 강인하게 얼굴 영역을 검출하며, 계산의 효율성과 검출 성능을 동시에 만족시키는 강인한 검출 알고리즘에 대해 제안한다. 제안한 알고리즘은 단일 카메라 환경에서 얼굴 형상을 입력정보로 사용하여 전처리 과정을 거쳐 얼굴 영역만을 분할한 후 자기 조직화 특징 지도(SOFM) 알고리즘을 이용하여 얼굴 형상을 인식하게 된다. 그러나 조명 변화에 민감하고 자유도가 큰 얼굴 영역을 정확히 인식하기란 쉽지 않으며 오차 범위도 크기 때문에 본 논문에서는 인식률을 높이기 위해 각각의 얼굴 형상에 대한 회전 정보를 데이터베이스화 한 후 주성분 분석을 적용하여 군집화 함으로서 인식오차를 줄였다. 또한 차원 축소로 인해 많은 계산량이 요구되지 않기 때문에 실시간 인식 시간도 줄일 수 있었다.

• Smart Structures and Systems
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• 제18권4호
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• pp.663-682
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• 2016

Continuum manipulators as a kind of mechanical arms are useful tools in special robotic applications. In medical applications, like colonoscopy, a maneuverable thin and flexible manipulator is required. This research is focused on developing a basic module for such an application using shape memory alloys (SMA). In the structure of the module three wires of SMA are uniformly distributed and attached to the circumference of a flexible tube. By activating wires, individually or together, different rotation regimes are provided. SMA model is used based on Brinson work. The SMA model is combined to model of flexible tube to provide a composite model of the module. Simulating the model in Matlab provided a platform to be used to develop controller. Complex and nonlinear behavior of SMA make the control problem hard especially when a few SMA actuators are active simultaneously. In this paper, position control of the two degree of freedom module is under focus. An experimental control strategy is developed to regulate a desired position in the module. The simulation results present a reasonable performance of the controller. Moreover, the results are verified through experiments and show that the continuum module of this paper would be used in real modular manipulators.

• KSTLE International Journal
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• 제2권2호
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• pp.93-102
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• 2001

Ball bearings have been widely used for the spindle motor bearing in various kinds of information storage devices. Recently many researchers have been trying to replace ball bearings with fluid film bearings because of their superior NRRO(non-repeatable runout) characteristics. In this study, a numerical analysis has been conducted for the complicate bearing system composed of herringbone groove journal bearing and spiral groove thrust bearing for the spindle motor of the information storage device. At first, spindle motor bearing is modeled as journal bearing part and thrust bearing part separately, and then observed various influences of geometric parameters. Previous studies had considered only the translational motion of the journal bearing. However, this study takes the additional 2-degree of freedom rotation into consideration to attempt to describe the real motion of the spindle bearing. As a result, rotational stiffness coefficients and rotational damping coefficients are obtained. In addition, a spindle bearing system made up of four bearings is modeled and interpreted at once and coefficients of dynamic characteristics of each bearing are obtained. Finally, an eigen analysis of bearing system is made with these results. Through this analysis, it is possible to estimate an unstable condition of the system for given geometric parameters and to propose a method which is able to avoid the unstable condition by a proper adjustment of geometric parameters.

• 한국산업융합학회 논문집
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• 제25권1호
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• pp.87-99
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• 2022

We propoes a study on the dynamic characteristics analysis and position control of 5-degree multi-joint manipulators for untact remote working at construction sites and manufacturing plants. The main frame of freedom multi-joint manipulator consists of five elements, boom cylinder, boom cylinder, arm cylinder, bucket cylinder, and rotation joint and link. In addition, the main purpose of the proposed system is to realize the work of the manufacturing process or construction site by remote control. Motion control of the entire system is a servo valve control method by hydraulic servo cylinders for one to four joints, and a servo motor control method is applied for five joints. The reliability of the proposed method was verified through performance experiments by computer simulation.