• 한국항공우주학회지
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• 제32권7호
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• pp.29-36
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• 2004

본 연구에서는 전진비행시 무힌지 로터 블레이드의 허브하중에 대한 복합재료 연성의 영향을 고찰하였다. 무힌지 복합재료 로터 블레이드를 단일 상자형 보로 모델링 하였으며, 전단 변형 및 비틀림 워핑과 같은 비고전적 효과를 고려하였다. 운동방정식은 해밀턴의 원리를 이용하여 구성하였으며, 로터 블레이드의 공간 및 시간차원에서의 유한요소법을 적용하여 완전평형해석을 수행하였다. 블레이드에 작용하는 공기력은 2 차원 준정상 공기력 이론을 바탕으로 하여 역류 및 압축성 효과를 고려하였다. MSC/NASTRAN을 이용하여 피치 -플랩 및 피치-래그와 같은 탄성 연성의 크기를 구하고, 고전적인 기하학적 연계와 비교하였다. 탄생 연성은 $N_b/rev$ 허브하중의 특성에 적지 않은 영향을 미침을 확인하였다 블레이드 복합재료의 적층각을 적절히 변화시킬 경우 약 10-40%의 허브하중을 감소시킬 수 있음을 보였다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.147-150
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• 2001

In the present work, a linear static analysis is presented for thin-walled prismatic box-beams made of generally anisotropic materials. A mixed beam theory has been used to model and carry out the analysis. Three different constitutive relations are assessed into the beam formulation. Simple layup cases having symmetric or anti-symmetric configuration have been chosen and tested to clearly show the effects of elastic couplings of the beam. Both 2D and 3D finite element structural analysis using the MSC/NASTRAN has been performed to validate the current analytical results. Results show that appropriate assumptions for the constitutive equations are important and prerequisite for the accurate prediction of beam stiffness constants and also for the beam behavior.

• 한국자기공명학회논문지
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• 제3권2호
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• pp.127-139
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• 1999

In this paper we discussed how multiple quantum coherences evolve in the presence of anisotropic distribution of dipolar couplings. The magnitude of dipolar couplings were varied by changing the tile angle of crystal axis. The stronger was dipolar coupling, the higher was frequency of multiple quantum coherence. That is, the order of multiple quantum coherence varies in proportion to the magnitude of dipolar couplings. The theoretical prediction for the multiple quantum coherence at magic angle 54.7$^{\circ}$ in solid NMR spectroscopy was verified in this study. The excitation pattern of n-quantum coherence, which can induce the effective size to characterize spin system, is expected in a larger and more complicated spin system for understanding of the relation of dipolar coupling and multiple quantum coherence.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.133-138
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• 1997

Belt-conveyer driving systems, which transport coal stored in the yard of a coal-fired fossil power plant to coal silos, experienced severe vibrations. From measurement, it was found that the vibrations showed beating phenomenoa and arose from hydraulic couplings installed between motors and gear boxes. In the present paper, described are results of case studies on vibration troubleshooting for the belt-conveyor driving systems: 1)resonance of the system; 2)field balancing.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 B
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• pp.388-391
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• 2003

Disturbance observer(DOB) is effective to enhance the performance of system in the presence of disturbances. Various types of disturbance observer have been proposed to improve sensitivity function of system. However, it has been observed that current DOBs tend to bring poor transient response due to cross-couplings. This paper proposes a new type of disturbance observer to reduce effect of cross-couplings and provide simpler structure than Dual DOB. Finally, we verify the performance of the proposed DOB through numerical simulations.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2012년도 춘계학술발표대회
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• pp.1213-1214
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• 2012

Global variables can be read or modified by any part of the program, making it difficult to remember or reason about every possible use. Sometime it has tight couplings between some of other variables, and couplings between variables and functions. The main focus of this paper is to use call graph and the control flow analysis to design a model from where we generate the test cases for testing global variables.

• 한국정밀공학회지
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• 제12권11호
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• pp.27-35
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• 1995

The fluid coupling combined with a pump and a turbine have many merits compared with other couplings, their uses are increesing rapidly in various industrial fields at home and abroad in pursuit of high-speed more efficiency durability of various mechanic devices. The authorities concerned have recognized the improtance of the fluid coupling and supported its developement and now some trial products began to show up. As the structrue and characteristics of the fluid coupling have little similarity to other kinds of couplings and its fluid behavior is unique, so its characteristic analysis is expected to be difficult. Until now no satisfactory study on the characteristics of the fluid coupling seems to have been conducted at home, so a study on this field needs to be done urgently. The purpose of this research is to construct the experimental test set-ups and establish a series of performance test program for the domestically developed fluid couplings and to provide a software to store and utilize these experimental data which can be used to improve the performance of the fluid coupling and solve on the job problems confronted in operation. The performance test consists of taking measurment of torque, rpm and efficiency of the fluid coupling for three different amount of working fluid inside with various loads to the output shaft and finally infestigating the torque, rpm and efficiency characteristics of the fluid coupling with respect to these parameters. The results of this study can contribute valuable references to the development of variable speed fluid coupling and torque converter currently pursued by the domestic industry.

• International Journal of Control, Automation, and Systems
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• 제4권2호
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• pp.255-270
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• 2006

In this paper, a design method of nonlinear autopilot for ship-to-ship missiles is proposed. Ship-to-ship missiles have strongly coupled dynamics through roll, yaw, and pitch channel in comparison with general STT type missiles. Thus it becomes difficult to employ previous control design method directly since we should find three different solutions for each control fin deflection and should verify the stability for more complicated dynamics. In this study, we first propose a control loop structure for roll, yaw, and pitch autopilot which can determine the required angles of all three control fins. For yaw and pitch autopilot design, missile model is reduced to a minimum phase model by applying a singular perturbation like technique to the yaw and pitch dynamics. Based on this model, a multi-input multi-output (MIMO) nonlinear autopilot is designed. And the stability is analyzed considering roll influences on dynamic couplings of yaw and pitch channel as well as the aerodynamic couplings. Some additional issues on the autopilot implementation for these coupled missile dynamics are discussed. Lastly, 6-DOF (degree of freedom) numerical simulation results are presented to verify the proposed method.

• International Journal of Fluid Machinery and Systems
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• 제5권2호
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• pp.91-99
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• 2012

The Fighter aircraft transmission system consists of a light weight, High Speed Flexible Coupling (HSFC) known as Power Take-Off shaft (PTO) for connecting Engine gearbox (EGB) with Accessory Gear Box (AGB). The HSFC transmits the power through series of specially contoured metallic annular thin flexible plates whose planes are normal to the torque axis. The HSFC operates at high speed ranging from 10,000 to 18,000 rpm. The HSFC is also catered for accommodating larger lateral and axial misalignment resulting from differential thermal expansion of the aircraft engine and mounting arrangement. The contoured titanium alloy flexible plates are designed with a thin cross sectional profile to accommodate axial and parallel misalignment by the elastic material flexure. This paper investigates the effect of misalignment on the transmission characteristics of the HSFC couplings. A mathematical model for the HSFC coupling with misalignment has been developed for analyzing the torque transmission and force interaction characteristics. An extensive testing has been conducted for validating characteristics of the designed coupling under various misalignment conditions. With this the suitability of the model adapted for the design iteration of HSFC development is validated. This method will reduce the design iteration cycles of HSFC and can be extended for the similar development of flexible couplings.

• 한국생산제조학회지
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• 제21권3호
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• pp.479-486
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• 2012

This paper presents a high-speed automatic micro-alignment system that is a part of an inspection machine for small-sized molded lenses of mobile phones, palm-top computers, and so on. This work was motivated by the shortcomings of existing highest-grade commercial machine. A simple tip/tilt/Z parallel mechanism is designed based on kinematic couplings, which is a 3-degree-of-freedom (3-DOF) moderate-cost alignment stage. It is used to automatically adjust the posture of each lens on the tray, which is impossible by the conventional instrument. Amplified piezoelectric actuators are used to ensure the accuracy and dynamic response. Forward kinematic analysis and simulation show that the parasitic motion is small enough compared to the actuator stroke. From the workspace analysis of the moving platform, it is clear that the output motion range satisfies the design requirements.