• 대한기계학회논문집A
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• 제25권8호
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• pp.1227-1234
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• 2001

A multi d.o.f robotic manipulator is considered for multi-axis vibration control of a slender structure, using the concept of the flow source based vibration control. In order not to cause the motion saturation of the manipulator system, a hybrid dynamics associated with the flexible and desired manipulator error dynamics is also modeled as the control object. It is numerically shown that the flexible vibrations and the base motions of a test structure can be effectively controlled with the proposed hybrid dynamics.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.163-167
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• 2003

A novel method for 3-dimensional dynamic analysis of marine slender structure gas been developed by using Euler parameters. The Euler parameter rotation, which is being widely used in aerospace vehicle dynamics and multi-body dynamics, has been applied to elastic structure analysis. Large deformation of flexible slender structures is described by means of Euler parameters. Euler parameter method is implemented effectively in incremental-iterative algorithm for 3D dynamic analysis. The normalization constraint of Euler parameters is efficiently satisfied by means of a sequential updating method.

• 한국해양공학회지
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• 제30권2호
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• pp.91-99
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• 2016

The global demand for oil and natural gas has increased, and resource development is moving to the deep sea. Floating and flexible offshore structures such as semi-submersible, spar, and FPSO structures have been widely used. The major equipment of floating structures is always exposed to waves, currents, and other marine environmental factors, which cause structural damage. Moreover, flexible risers are susceptible to an exciting force due to the motion of the floating body. The inline and transverse responses from the three-dimensional behavior of a floating structure occur because of various forces. Typical risers are made of steel pipe and applied in the oil and gas development field, but flexible materials such as polyethylene are suitable for OTEC risers. Consequently, the optimal design of a flexible offshore plant requires a dynamic behavior analysis of slender bodies made of the different materials commonly used for offshore flexible risers. In this study, a three-dimensional motion measurement device was used to analyze the displacements of riser models induced by external force factors, and forced oscillation of a riser was linked to forced oscillation under a steady flow and regular wave condition.

• Wind and Structures
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• 제14권2호
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• pp.85-112
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• 2011

Wind turbine structures are long slender columns with a rotor and blade assembly placed on the top. These slender structures vibrate due to dynamic environmental forces and its own dynamics. Analysis of the dynamic behavior of wind turbines is fundamental to the stability, performance, operation and safety of these systems. In this paper a simplied approach is outlined for free vibration analysis of these long, slender structures taking the soil-structure interaction into account. The analytical method is based on an Euler-Bernoulli beam-column with elastic end supports. The elastic end-supports are considered to model the flexible nature of the interaction of these systems with soil. A closed-form approximate expression has been derived for the first natural frequency of the system. This new expression is a function of geometric and elastic properties of wind turbine tower and properties of the foundation including soil. The proposed simple expression has been independently validated using an exact numerical method, laboratory based experimental measurement and field measurement of a real wind turbine structure. The results obtained in the paper shows that the proposed expression can be used for a quick assessment of the fundamental frequency of a wind turbine taking the soil-structure interaction into account.

• 제어로봇시스템학회논문지
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• 제5권2호
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• pp.220-227
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• 1999

The position control accuracy of a robot arm is significantly deteriorated when a long slender arm robot is operated at a high speed. In this case, the robot arm needs to be modeled as a flexible structure, not a rigid one, and its control system needs to be designed with its elastic modes taken into account. In this paper, the vibration control scheme of a one-link flexible manipulator using adaptive input shaper in conjunction with PID controller is presented. The robot consists of a flexible arm manufactured with a thin aluminium plate, an AC servo motor with a harmonic drive for speed reduction, an optical encoder and an accelerometer. On-line identification of the vibration mode is done using the pruned decimation-in-time FFT algorithm to estimate the parameter of the input shaper. Experimental results of the flexible manipulator with a PID controller and input shaper are provided to show the effectiveness of the advocated controllers.

• Wind and Structures
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• 제15권3호
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• pp.189-208
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• 2012

Lock-in and drag amplification phenomena are studied for a flexible cantilever using a simplified fluid-structure interaction approach. Instead of solving the 3D domain, a simplified setup is devised, in which 2D flow problems are solved on a number of planes parallel to the wind direction and transversal to the structure. On such planes, the incompressible Navier-Stokes equations are solved to estimate the fluid action at different positions of the line-like structure. The fluid flow on each plane is coupled with the structural deformation at the corresponding position, affecting the dynamic behaviour of the system. An Arbitrary Lagrangian-Eulerian (ALE) approach is used to take in account the deformation of the domain, and a fractional-step scheme is used to solve the fluid field. The stabilization of incompressibility and convection is achieved through orthogonal quasi-static subscales, an approach that is believed to provide a first step towards turbulence modelling. In order to model the structural problem, a special one-dimensional element for thin walled cross-section beam is implemented. The standard second-order Bossak method is used for the time integration of the structural problem.

• 한국어류학회지
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• 제17권1호
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• pp.36-42
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• 2005

한국의 메기과 (Siluridae) 어류의 수염을 조직학적으로 조사하였다. 메기, Silurus asotus의 상악 수염은 연골성 중축을 감싸는 진피와 표피로 구성 되었다. 표피층에는 점액세포, 과립형세포 및 미뢰가 있었다. 세포질이 약한 호염기성을 보이는 점액세포와 호염기성을 보이는 미뢰는 각각 표피의 표면과 표피 말단 부위에 위치 하였다. 표피와 진피는 기저막으로 구분되며 진피는 소성결합조직으로 구성 되었으며 신경세포와 혈관이 내재하고 있었다. 수염의 가장 내부에 연골성 중축이 존재 하였으며 근육층으로 둘러싸여 있었다. 미유기, S.microdorsalis의 상악 수염 구조는 메기의 상악 수염 구조와 비교시 별다른 차이는 보이지 않았으나, 상악 상부와 하부에서의 표피 % 두께 및 상악 상부와 중부에서의 미뢰 수에 있어 미유기는 메기에 비해 차이를 보였다. 본 연구결과 메기와 미유기의 상악 수염은 딱딱하고 굴절성형(stiff and flexible type)으로 파악 되었다.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.14-20
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• 2014

Recent developments for high altitude, long endurance conventional UAVs(HALE UAVs) have revealed new issues regarding aircraft structure design and analysis. First of all, due to intensive mission requirements, the structures of HALE UAVs have lightweight and very flexible main wing with high aspect ratio, and slender fuselage. For this kind of structures, aeroelastic characteristics are different from conventional aircrafts. Hence, currently developed analysis methods are not suitable to fully understand strucutral dynamics of the very flexible aircraft, and to guarantee structural reliability. Therefore, various structural studies considering nonlinear behaviors which are generally ignored for the conventional aircraft strucutral analyis have been attracting researchers interests. Nonlinear flutter of the very flexible wing is one of the subject to be studied in combination with strong coupling between aeroelastic characteristics and flight dynamics. Herein, as preliminary study, modeling and nonlinear system analysis of the 2D airfoild with torsional nonlinearity have been discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 추계학술대회 논문집
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• pp.226-231
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• 2013

Recent developments for high altitude, long endurance conventional UAVs (HALE UAVs) have revealed new issues regarding aircraft structure design and analysis. First of all, due to intensive mission requirements, the structures of HALE UAVs have lightweight and very flexible main wing with high aspect ratio, and slender fuselage. For this kind of structures, aeroelastic characteristics are different from conventional aircrafts. Hence, currently developed analysis methods are not suitable to fully understand strucutral dynamics of the very flexible aircraft, and to guarantee structural reliability. Therefore, various structural studies considering nonlinear behaviors which are generally ignored for the conventional aircraft strucutral analyis have been attracting researchers interests. Nonlinear flutter of the very flexible wing is one of the subject to be studied in combination with strong coupling between aeroelastic characteristics and flight dynamics. Herein, as preliminary study, modeling and nonlinear system analysis of the 2D airfoild with torsional nonlinearity have been discussed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.280-285
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• 2000

With recent development of technology of high stiffness material and the structural design, the construction of high rise structures such as tall building, tower has increased. The more flexible and slender structure is vulnerable to the internal and external dynamic loads induced by earthquake, wind and traffic load. There have been great effort and many researches to minimize the influence of dynamic loads on the structure. The traditional and stable method, the application of the passive damper, is not able to comply with various dynamic loads, while the mass damper which active control technology is integrated can effectively comply with load types. Therefore, the application of active control of huge structures with AMD(Active mass damper) or HMD(Hybrid Mass damper) is increasing. Up to now, most of actuators are servomotor and hydraulic actuator. But it is known that the electromagnetic actuator applies non contacting control force, which makes the control system easier with no characteristic change depending on time. In this paper, Hybrid mass damper with electromagnetic actuator was designed and applied to building scaled structure. The performance of designed HMD tested by shake table test is included.