• 한국정밀공학회지
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• 제20권10호
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• pp.47-55
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• 2003

In the development of positioning device for precision manufacturing and measuring, the friction from mechanical contact causes serious decrease of performance. In this study, we studied about variable reluctance type contact-free linear actuator to overcome drawbacks from friction. In the view of electromagnetics, we analyzed and derived theoretical magnetic force equation and designed structure for generating suspension and propulsion force simultaneously. In the view of dynamics, we derived equation of motion and identified the stability of the system. Finally, we verified the feasibility of the proposed system.

• 한국소음진동공학회논문집
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• 제13권9호
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• pp.663-670
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• 2003

As the micro-technologies in the high precision manufacturing processes are developed, the demand for micro actuating device is increasing. But, it is difficult to achieve high resolution and wide operating range simultaneously with the conventional actuating systems which are contacting and type of dual servo system. So, the contact-free surface actuators whose movers are suspended or levitated were proposed. These systems can be applied to high precision stages and alignment apparatuses. The suspended mover can be assumed to be rigid body, but the mover is a structure in this study, therefore the vibration caused during the operating process has a serious adverse effect on the performance and it is very important to identify the vibrational characteristics. In this paper, a contact-free surface actuator is modeled in finite element method and updated by using the experimental modal data. Finally, the static and dynamic characteristics of the finite element model are predicted and then discussed.

• 한국초전도ㆍ저온공학회논문지
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• 제15권4호
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• pp.59-62
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• 2013

The conductive link is used as a cooling medium between a cryocooler and magnet in a cryogen-free superconducting magnet system. The low temperature superconducting (LTS) magnet has one solenoidal configuration with a metal former which has a 52 mm room temperature bore. The superconducting coil is installed in the cryostat maintaining high vacuum and cooled by a two-stage cryocooler. In order to maintain the operating temperature of magnet at the designed level, the cold head temperature of the cryocooler must be lower so that heat can be removed from the superconducting coil. Also, temperature difference is occurred between the magnet and cryocooler and its magnitude is dependent upon the contact resistance at the interfacial surface between metals in the conductive link. In the paper, the performance of the LTS magnet is investigated with respect to the conductive link between the magnet former and the cold head of the cryocooler. The effects of the contact pressure and interfacial materials on the temperature distribution along the conductive link are also presented.

• Journal of Mechanical Science and Technology
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• 제17권5호
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• pp.708-717
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• 2003

With the development of precision manufacturing technologies, the importance of precision positioning devices is increasing. Conventional actuators, dual stage or mechanically contacting type, have limitation in coping with performance demands. As a possible solution, magnetic suspension technology was studied. Such a contact-free system has advantages in terms of high accuracy, low production cost and easy adaptability to high precision manufacturing processes. This paper deals with magnetically suspended multi-degrees of freedom actuator which can realize large linear motion. In this paper, the operating principle is explained with the magnetic force analysis, and the equations of motion are derived. Experimental results of the implemented system are also given.

• 대한기계학회논문집A
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• 제27권6호
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• pp.871-878
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• 2003

With the development of micro -technology, the demand for micro actual ing device is increasing. But, it is difficult to achieve high resolution and wide bandwidth with the conventional contact systems. So, the contact-free systems which are suspended or levitated by magnetic force or air bearing were proposed. These systems can be applied to high precision stages and alignment apparatuses. This paper describes a magnetically suspended system with four degrees of freedom which are composed of three rotations (roll, pitch, yaw), and one translation ( z). The operating principle and the structure of the system are similar to variable reluctance type electric machines. In this study, the force analysis is executed using magnetic circuit and virtual work principle, and the equations that describe the dynamics of the system are presented. The multivariable PID controller is adapted to the system and the experiment is executed.

• 한국정밀공학회지
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• 제20권7호
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• pp.120-127
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• 2003

A novel three degrees of freedom sensing method utilizing binary grid pattern image and vision camera is presented. The binary grid pattern image is designed by Pseudo-Random Binary Arrays and referenced to encode in-plane position of a moving stage of the contact-free planar actuator. First, the yaw motion of the stage is detected using fast image processing and then the other planar positions, x and y, are decoded with a sequence of images. This method can be applied to the system that needs feedback of in-plane position, with advantages of a good accuracy and high resolution comparable with the encoder, a relatively compact structure, no friction, and a low cost. In this paper, all the procedures of the above sensing mechanism are described in detail, including simulation and experiment results.

• 한국정밀공학회지
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• 제20권5호
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• pp.180-188
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• 2003

In the precision motion device, the frictional problem by mechanical friction causes serious effects on the system performance. Various researches have been executed to solve this problem, but classical fluid lubrication method has some disadvantages in precision motion under clean environment. Therefore, the magnetic bearing and contact-free systems have been focused on with its pollution-free characteristics. In this paper, we treat modeling and analysis of electromagnets not only for magnetic bearing but also fer contact-free electromagnetic actuators. Three types of electromagnet for various applications are modeled and analyzed by magnetic circuit theory and the validity is verified by experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.97.3-97
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• 2002

This paper presents the vibration characteristics of an intelligent cantilever beam in contact with a fluid using a PZT actuator and PVDF film. The dynamic behaviors of a flexible beam-water interaction system are examined. The effect of the liquid level on free vibration of the composite beam in a partially liquid-filled circular cylinder is investigated. The coupled system is subject to an undisturbed boundary condition in the fluid domain. It was found that the coupled natural frequencies decreased with the fluid level for the identical composite beam due to added mass effect. In case of the free-free boundary condition, the natural frequency gently decreased at fluid water level betw...

• 대한기계학회논문집A
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• 제27권11호
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• pp.1941-1948
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• 2003

This paper is about feasibility study of positioning device using magnetic suspension system which uses only vertical magnetic forces. The proposed system has inherited advantages from contact-free system, simple structure, and high expansibility in operating range different from conventional positioning devices. In this paper, the structure and operating principle are described and the linearized magnetic force and dynamic model are obtained. With the linear control theory, the experiments are executed. finally, the experimental results are shown.

• 폴리머
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• 제24권2호
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• pp.245-251
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• 2000

에폭시 (EP) 수지와 폴리우레탄(PU) 으로 제조된 블렌드 시스템의 접촉각과 기계적 특성을 연구하였다. EP의 경화제로 20 phr의 DDM (4,4'-diamino diphenyl methane)이 사용되었으며 EP/PU의 함량은 100/0~100/60까지 변화시켰다. 접촉각은 Rame-Hart goniometer를 사용 하였으며 젖음액으로는 증류수와 diiodomethane을 사용하였다. 본 연구에서는 geometric 방법을 사용한 Owens-Wendt와 Wu's model이 블렌드 시스템의 표면 자유에너지를 알아보는데 사용되었다. 시편의 기계적 성질과 강인성은 임계 응력 세기 인자(critical stress intensity factor, $K_{IC}$)와 충격 강도 시험을 통하여 알아보았다. 그리고 특히 충격 강도는 상온과 극저온에서 알아보았다. 그 결과로서, 블렌드 시스템에 있어서 표면 자유에너지의 극성 요소는 저온에서 충격 강도를 증가시키는 PU의 함량에 크게 영향을 주었음을 알 수 있었다.