• 대한기계학회논문집
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• 제16권5호
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• pp.910-923
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• 1992

본 연구에서는 가장 응용 빈도가 큰 크랭크-레버 4절 기구를 제작하고 강성과 유연성 두가지 베어링을 사용하여 연결봉과 레버의 중점의 변형률을 스트레인 게이지 로 측정하여 앞의 이론 논문에서 수행한 수치해석의 결과와 비교 검토하였다.

• 한국항공우주학회지
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• 제30권7호
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• pp.113-122
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• 2002

KSR-III 로켓의 자세제어 시스템 모델링과 최적 벤딩 필터 설계가 이루어졌다. 모델링에는 로켓 강체 동역학, 공력, 슬로싱, 구조적 벤딩, 구동기 동역학, 센서 동역학, 그리고 탑재 컴퓨터 특성이 고려되었다. 시간의 변화에 따른 자세제어 시스템 파라미터들의 변화를 보상하기 위하여 이득 스케쥴링 기법이 사용되었다. 벤딩 모드를 안정화시키기 위한 필터가 매개변수 최적화 방법을 이용하여 설계되었다. 설계된 자세제어 시스템은 주파수 영역에서 요구되는 이득 및 위상 안정성 여유를 가지게 되었다.

• Journal of Astronomy and Space Sciences
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• 제14권2호
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• pp.386-394
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• 1997

본 연구에서는 유연모드를 고려한 위성체 모델링 방법들을 소개하고, 이에 따라 3축 안정화 위성의 유연모드를 모델링하였다. 이 모델을 강체에 대해 설계되었던 반작용휠을 이용한 자세제어루프에 적용하였다. 본 연구에서는 유한요소모델이 완성되기 전 단계에서 집합모드모델 중 전역모드모델을 이용하는 것을 제안하였고, 이를 유한요소법을 이용하여 계산된 모델과 제어기 필터 설계의 관점에서 비교하였다. 새로운 유연모드가 적용됨에 따라 제어기 요구조건을 만족시키기 위한 필터가 필요하여 반작용휠의 모터제어기 루프와 축제어기 루프에 각각 1차 필터를 설계하여 추가하였다. 제어루프 설계 및 시뮬레이션을 위해 MATLAB/Simulink를 사용하였다.

• 동력기계공학회지
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• 제7권3호
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• pp.48-53
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• 2003

This paper deals with the control of a horizontally placed flexible rotor levitated by electromagnets in a multi-input/multi-output (MIMO) active magnetic bearing(AMB) system. AMB is a kind of novel high performance bearing which can suspend the rotor by magnetic force. Its contact-free manner between the rotor and stator results in it being able to operate under much higher speed than conventional rolling bearings with relatively low power losses, as well as being environmental-friendly technology for AMB system having no wear and no lubrication requirements. In this MIMO AMB system, the rotor is a complex mechanical system, it not only has rigid body characteristics such as translational and slope motion but also bends as a flexible body. Reduced order nominal model is computed by consideration of the first 3 mode shapes of rotor dynamics. Then, the $H_{\infty}$ control strategy is applied to get robust controller. Such robustness of the control system as the ability of disturbance rejection and modeling error is guaranteed by using $H_{\infty}$ control strategy. Simulation results show the validation of the designed control system and the modeling method to the rotor.

• 한국소음진동공학회논문집
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• 제16권4호
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• pp.329-338
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• 2006

The resilient mounts of a diesel engine installed onboard a ship should be designed for both static and dynamic loads. If possible, the resonance frequencies of the six rigid body modes of the installation and the flexible modes of the engine support structure should not lie within the engine operation range. In this paper a design criterion is proposed to evaluate an isolation system which involves the summation of dynamic forces transmitted through the resilient mounts and elastic potential energy index stored in the mounts. A case study is also presented in which a diesel engine generator, which had an elastic foundation and was mounted in a 5500 TEU container vessel, was studied both theoretically and experimentally. The theoretical analysis of the test model was performed by using a single mass 6 degree of freedom system. Actual measurements of mechanical vibration of the engine and its foundation onboard were carried out, which showed the importance of including the flexibility of the engine support structure in the mode.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.283-289
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• 1997

A 500Wh class high-speed Flywheel Energy Storage System (FESS) driven by a built-in BLDC motor/generator has been designed, which runs from 30000 to 60000rpm nominally. Due to the motor/generator inside, the flywheel rotor made of composites supported by PM/EM hybrid bearing system has a shape of bell or pendulum and thus requires accurate rotordynamic analyses and prediction of its dynamic behavior to secure the operating reliability. Rotordaynamic analyses of the flywheel rotor-bearing system revealed that the bell shaped rotor has two conical rigid-body modes in the system operating range and the first conical mode, of which nodal point lies in the radial EM bearing position, can adversely affect the dynamic response of the rotor at the corresponding critical speed. To eliminate the possibility of wild behavior of the rotor, two guide bearings are adopted at the upper end of the rotor and motor/generator. It was also revealed that the EM bearing stiffness of 0.5~1.0E+6 N/m and damping of 2000 Ns/m are favorable for smooth operation of the system around the 2nd critical speed.

• 한국공간구조학회논문집
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• 제3권2호
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• pp.91-99
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• 2003

The purpose of this study is to analyze the characteristics of the connector having an influence on the elasto-plastic buckling load of ball-jointed single layer latticed domes. As an analytic model, domes are composed of tubular member elements, balls and connectors. The joint system of members in single layer latticed domes has influence on the buckling load. Therefore, in this paper, the variation of the elasto-plastic buckling load by effects of the connectors characteristics is analyzed. The structural behavior of the connector is investigated by following points: (1) the length of rigid zone, (2) looseness of screw and (3) the diameter of connector. In addition, the elasto-plastic buckling analysis is carried out through the variation of the connectors section of yielding part, and then the buckling mode of the dome is examined. As a result, it is emphasized that the characteristics of the connector have significant effects on the buckling load of latticed domes.

• 대한조선학회논문집
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• 제44권6호
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• pp.627-634
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• 2007

A bonded plate or a coated part can be debonded by external impact or thermal expansion. To analyse adhesive strength, the blister test is generally adopted. In this paper, a blister test is modelled theoretically and then the stability and bifurcation of the blister are studied under several different cases. The blister is simplified to consist of a pure bending plate attached elastically to the rigid substrate. Expression of the energy release rate is obtained as a form of an explicit function for a circular-type blister or tunnel-type blister grown by controlling the internal pressure or internal volume. Stability and bifurcation are also studied in the frame of the quasi-static evolution. The study shows that the circular- type blister propagates with the first mode of bifurcation and that the tunnel-type blister propagates with a regular wave. It is proved that the waves have the same form on two side lines of the tunnel and that the wave length can be obtained. When the internal pressure is controlled, the blister is unstable, but when the internal volume is controlled, it is stable.

• 한국생산제조학회지
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• 제18권6호
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• pp.642-651
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• 2009

The history of excavator design is not long enough which still causes most of the design considerations to be focused on static analysis or simple functional improvement based on static analysis. However, the real forces experiencing on each component of excavator are highly transient and impulsive. Therefore, the prediction and the evaluation of the movement of the excavator by dynamic load in the early design stage through the dynamic transient analysis of the excavator and ensuring of design technique plays an importance role to reduce development-cost, shorten product-deliver, decrease vehicle-weight and optimize the system design. In this paper, Commercial software DADS and ANSYS help to develop the track model of the crawler type excavator, and to evaluate the performance and the dynamic characteristics of excavator with various simulations. For that reason, the track of crawler type excavator is modelled with DADS Track Vehicle Superelement, and the reaction forces on the track rollers were predicted through the driving simulation. Also, the upper frame and cabin vibration characteristics, at the low RPM idle state, were evaluated with engine rigid body modelling. And flexibility body effects were considered to determine the more accurate joint reaction forces and accelerations under the upper frame swing motion.

• 한국정밀공학회지
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• 제17권11호
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• pp.206-212
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• 2000

This paper presents a hybrid actuator scheme to actively control the end-point position and vibration of a two-link flexible robot arm. Control scheme consists of four different actuators; two servo-motors at the hubs and two piezoceramics bonded to the surfaces of the flexible links. Two sliding hyperplanes are designed for two servo-motors which have time varying parameters to maintain control performance in any configuration. The surface gradients of the hyperplanes are determined by pole assignment technique to guarantee the stability on the hyperplanes themselves. During the motion, undesirable oscillations caused by the torques based on the rigid link dynamics are actively suppressed by applying feedback control voltages to the piezoceramic actuators. Consequently, desired tip motion is achieved. In order to demonstrate the effectiveness of the proposed methodology, experiments are performed for the regulating and tracking control problems.