• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2002년도 하계학술대회 논문집 B
• /
• pp.888-890
• /
• 2002

We derived a theory of increasing electromagnetic force acting on arc column for reducing arcing time between electric contacts. A simulation method of arc velocity is presented by calculating blowout force using 3D FEM and drag acting on arc column. This paper is proposed 3 types arc extinguish chamber of different fulx path and is presented electromagnetic force and arc velocity of each model.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1991년도 하계학술대회 논문집
• /
• pp.110-113
• /
• 1991

An electromagnet is one of the important devices in magnetic levitation system. Its weight takes large part in the total weight of a vehicle. That is the reason why it is important to design the electromagnet optimally to maximize the attraction force with constant volume. This study presents the optimum value of the design variables which can produce the maximal attraction force under constant magnet volume. For this, non-linear programming in optimization technique is used. And to confirm reliability of the results, the optimally designed electromagnet is analyzed by FEM. The attraction force of the optimally designed electromagnet is increased maximally 72% compared with that of the basic model. And the results obtained by non-linear programming has 30% error compared with that of FEM.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
• /
• pp.424-424
• /
• 2000

The implementation of a insect-based flying microrobot has been previously proposed as using magnetic force. The flying principle of a butterfly is different from that of a airplane, which obtain lifting force above the wings by a air stream with low pressure. Butterflies obtain lifting force below the wings by flapping. They can fly when drag during the down stroke is greater that during the up stroke. The structure of flying microrobot must satisfy these condition. And that must be manufacture lightly and keep balance for rising to the air sufficiently. Moreover the efficiency of an electromagnet is high and the flux density is sustained uniformly and widely Nevertheless these condition is satisfied, the implementation of a flying microrobot is very difficult as the flying microrobot has to fly without guides or sensor. We propose differently a new model il] comparison with that other paper has suggested. This imitates the form of the Korean shield-shaped kite.

• Structural Engineering and Mechanics
• /
• 제68권3호
• /
• pp.359-368
• /
• 2018

This paper deals with the dynamic stability of nanocomposite pipes conveying pulsating ferrofluid. The pipe is reinforced by carbon nanotubes (CNTs) where the agglomeration of CNTs are considered based on Mori-Tanaka model. Due to the existence of CNTs and ferrofluid flow, the structure and fluid are subjected to axial magnetic field. Based on Navier-Stokes equation and considering the body forced induced by magnetic field, the external force of fluid to the pipe is derived. For mathematical modeling of the pipe, the first order shear deformation theory (FSDT) is used where the energy method and Hamilton's principle are used for obtaining the motion equations. Using harmonic differential quadrature method (HDQM) and Bolotin's method, the motion equations are solved for calculating the excitation frequency and dynamic instability region (DIR) of the structure. The influences of different parameters such as volume fraction and agglomeration of CNTs, magnetic field, structural damping, viscoelastic medium, fluid velocity and boundary conditions are shown on the DIR of the structure. Results show that with considering agglomeration of CNTs, the DIR shifts to the lower excitation frequencies. In addition, the DIR of the structure will be happened at higher excitation frequencies with increasing the magnetic field.

• 한국소음진동공학회논문집
• /
• 제16권7호
• /
• pp.754-761
• /
• 2006

This paper presents the dynamic characteristics of MR impact damper for vehicle collision system. Various types of mechanism have been proposed to reduce force transmitted to the vehicle chassis and finally to protect occupants from injury. In the case of head-on collision, the bumper makes main role of isolation material for collision attenuation. In this study, the proposed bumper system consists of MR impact damper and structures. The MR impact damper utilizes MR fluid which has reversible properties with applied magnetic field. The MR fluid operates under flow mode. The bellows is used for generation of fluid flow. A mathematical model of the MR impact damper is derived incorporating with Bingham model of the MR fluid. Field dependent damping force is investigated with time and frequency domain. The MR impact damper is then incorporated with vehicle crash system. The governing equation of motion of vehicle model is formulated considering occupant model. Dynamic characteristics of vehicle collision system investigated with computer simulation.

• 구강회복응용과학지
• /
• 제24권2호
• /
• pp.169-181
• /
• 2008

치과용 자석의 개선으로 자성 어태치먼트를 이용한 임플란트 피개의치의 사용이 늘고 있다. 또한 여러 형태의 자성 어태치먼트가 개발되어 임상 상황에 따라 적절히 선택하여 사용할 수 있게 되었다. 이에 시중에 판매되는 세 가지 형태의 임플란트용 자성 어태치먼트를 이용해 자성 어태치먼트의 형태와 임플란트 수에 따른 임플란트 피개의치의 유지력을 비교 분석하였다. 식립된 임플란트가 1개인 경우를 1군, 2개인 경우 2군, 4개인 경우를 3군으로 하였고, 자성 어태치먼트의 형태에 따라 flat type, cushion type, dome type으로 세분하였다. Instron으로 수직방향, 사선방향, 전후방향의 인장력을 가하여 자성 어태치먼트의 형태에 따른 유지력의 차이, 힘의 방향에 따른 유지력의 차이, 자성 어태치먼트의 수에 따른 유지력의 변화를 비교 분석하여 다음의 결과를 얻었다. 1) 임플란트의 수와 상관없이 수직력은 flat type이 가장 컸으며, 측방력은 dome type이 가장 작은 것으로 나타났다. 2) 임플란트가 1개일 때 flat type의 수직력이 전후방회전력보다 크게 나타났고, 임플란트가 2개일 때는 dome type과 flat type이, 임플란트가 4개일 때는 cushion type과 flat type에서 수직력이 전후방회전력보다 크게 나타났다. 3) 임플란트 수에 따른 유지력 측정결과, 자석의 형태에 상관없이 임플란트 수가 많을수록 유지력은 증가하였다. 이상의 결과로 볼 때, 큰 유지력이 필요한 환자에게는 flat type이, 유해한 수평력이 존재하는 환자에게는 dome type의 이용이 유리하고, 임플란트가 1개일 때 flat type, 2개일 때 dome type과 flat type, 임플란트가 4개일 때 cushion type과 flat type이 피개의치의 안정성이 더 좋은 것으로 나타났다. 또한 자성 어태치먼트의 형태에 상관없이 임플란트의 수가 증가할수록 더 큰 유지력을 나타냈다. 따라서 임플란트 피개의치 사용 시 적절한 유지력과 안정성을 얻기 위해서 임플란트의 수와 자성 어태치먼트 형태의 고려가 필요하다고 사료된다.

• International Journal of Aeronautical and Space Sciences
• /
• 제18권3호
• /
• pp.414-424
• /
• 2017

This paper introduces an experimental device which can measure accurate aerodynamic forces without support interference in wide experimental region for wind tunnel test of micro aerial vehicles (MAVs). A stereo pattern recognition (SPR) method was introduced to a magnetic suspension and balance system (MSBS), which can eliminate support interference by levitating the experimental model, to establish wider experimental region; thereby MSBS-SPR integrated system was developed. The SPR method is non-contact, highly accurate three-dimensional position measurement method providing wide measurement range. To evaluate the system performance, a series of performance evaluations including SPR system measurement accuracy and 6 degrees of freedom (DOFs) position/attitude control of the MAV model were conducted. This newly developed system could control the MAV model rapidly and accurately within almost 60mm for translational DOFs and 40deg for rotational DOFs inside of $300{\times}300mm$ test section. In addition, a static wind tunnel test was conducted to verify the aerodynamic force measurement capability. It turned out that this system could accurately measure the aerodynamic forces in low Reynolds number, even for the weak forces which were hard to measure using typical balance system, without making any mechanical contact with the MAV model.

• Journal of Electrical Engineering and Technology
• /
• 제3권1호
• /
• pp.60-67
• /
• 2008

The vibrations and noise origin in electric material is due to several coupled physical phenomena. The revolving electric machine complete modeling is complex; it does not allow simple parametric machine structure studies for various operation modes. This work presents a simple electromagnetic model which makes possible the machine principal parts flow estimation from flux density. Special interest is given in determining Switched Reluctance Machine (S.R.M) radial acceleration in accordance with the current supply. Our focus will be only on the magnetic origin efforts that are dominating in the S.R.M. The efforts calculation versus the current is presented in the case of a machine with a linearized rate. These efforts are considered as a tangential force producing the torque and a radial force that generates no torque. The application is realized on a 6/4 low power S.R.M type (6 stator teeth and 4 teeth rotor). The mechanical response is substituted in a transfer function. The model takes account of the power supply of the machine, the relation between the current supply and the efforts as well as the vibratory response of the machine to these efforts. Finally, the model is validated by comparison with similar experimental results within the framework of the definite assumptions.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.147-152
• /
• 2006

This paper presents the dynamic characteristics of MR impact damper for vehicle collision system. Various types of mechanism have been proposed for reduce transmitted force to vehicle chassis and finally protect occupants from injury. In the case of frontal collision, the bumper make main role of isolation material for collision attenuation. In this study, proposed bumper system composed of MR impact damper and structures. The MR impact damper is to adopted MR fluid which has reversible properties with applied magnetic field. MR fluid operates under flow mode with Bingham flow and bellows is used for generation of fluid flow. Mathematical model of MR impact damper incorporated with MR fluid is established. Field dependent damping force is investigated with time and frequency domain. The MR impact damper is then incorporated with vehicle crash system. The governing equation of motion of vehicle model is formulated considering occupant model. Dynamic characteristics of vehicle collision system investigated with computer simulation.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2015년도 제46회 하계학술대회
• /
• pp.772-773
• /
• 2015

This paper presents a dynamic model of 2-D magnetostriction in electrical steel sheet (ESS) under rotating flux magnetization conditions and its implementation in finite element method (FEM). For an arbitrary waveform of magnetic flux density (B), the corresponding magnetostriction waveform can be predicted by the model. In order to apply the model to FEM easily, the model is based on trilinear interpolation method. As an example, the model is applied to a three-phase transformer constructed by highly grain-oriented electrical steel sheets and the numerical results by the magnetostriction model are discussed.