• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.217-224
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• 2016

In this study, a transfer matrix method (TMM) for a twisted uniform beam considering the effect of rotary inertia is developed, and the differential equation and the displacements and forces are derived from Hamilton's principle. The particular transfer matrix is derived by applying the distributed mass and transcendental function while using a local coordinate system. In addition, the results obtained from this method are independent for a number of subdivided elements, and this method can determine the exact solutions for the free vibration characteristics of a twisted uniform Rayleigh beam. To validate the accuracy of the proposed TMM, the computed results are compared with those reported in the existing literature, and the comparison results indicate notably good agreement. In addition, the method is used to investigate the effects of rotary inertia for a twisted beam.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.8
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• pp.768-773
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• 2011

This work presents an experimental investigation on vibration control of the active hybrid mount system for naval ships. To reduce unwanted vibrations, this paper proposes an active mount which consists of rubber element, piezostack actuator and inertial mass. The rubber element supports a mass. The piezostack actuator generates a proper control force and supply it to the mount system. To avoid being broken piezostack actuator, an actuator of the proposed mount is devised as an inertial type, in which a piezostack actuator is positioned between inertial mass and rubber element. Vibration control performances of the active mount system are evaluated via experiment. To attenuate the unwanted vibrations transferred from upper mass, the feedforward control is designed. In order to implement a control experiment, the active mount system supported by four active mounts is constructed. For realization of the controller, one-chip board is manufactured and utilized. Subsequently, vibration control performances of the proposed active mount system are experimentally evaluated in frequency domains.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.764-767
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• 2005

This paper deals with the flexural-torsional free vibrations of circular strip foundations with a variable breadth. The breadth of strip foundation varies with the linear functional fashion, which is symmetric about the mid-arc. Differential equations governing free vibrations of such foundations are derived, in which Winkler foundation is considered as the model of elastic soils. Effects of the rotatory and torsional inertias and shear deformation are included in the governing equations. Differential equations are numerically solved to calculate the natural frequencies. In the numerical examples, the free-free end constraint is considered. Effects of the rotatory and torsional inertias and shear parameter on the natural frequencies are reported. Parametric studies between frequency parameters and various system parameters are investigated.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.3
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• pp.65-72
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• 2001

Generally, it is said that control of the inertia system is to track the reference input quickly while suppressing the vibration due to the system itself. In this case, the difficulty fur designing a controller is caused by modeling uncertainty and parameter variation. The purpose of this paper is to propose a design method to suppress the vibration of three-mass inertia system based on the LMI theory. That is, the generalized plant model by which we can cope with conservativeness of the existing H$_{*}$ theory is proposed and analyzed in terms of LMI. The results of simulation fur the three-mass inertia system show that the proposed design approach is quite effective under the given situations.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.129-132
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• 2001

she purpose of this paper is to propose an approach to suppress the vibration of three-mass inertia system based on the LMI theory. and confirm its validity through simulations under the condition of parameter variation. First, the existing $H_{\infty}$ servo problem is modified to a structure to which the LMI theory can be applied by virtue of the interval model principle. By adopting this structure, we can divide given specifications fur the vibration suppression problem into $H_2$and $H_{\infty}$ performance criteria. The results of simulation for the three-mass inertia system show that the proposed design approach is quite effective.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1157-1164
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• 2003

Dynamic Load/unload (L/UL) mechanism is an alternative to the contact start stop (CSS) technology which eliminates stiction and wear failure modes associated with CSS. Other benefits of L/UL include increased areal density due to smooth disk surfaces, thinner overcoats, and lower head flying height Improved shock resistance due to elimination of head slap, and reduced power consumption. Inertia latch mechanism becomes important for mobile disk drives because of non operating shock performance. Various types of latch designs have been introduced in hard disk drives to limit a rotary actuator from sudden uncontrolled motion. In this paper, a single spring inertia latch is introduced for a small form optical disk drive, which uses a rotary actuator for moving an optical pick-up. A new small inertia latch with single spring is designed to ensure both feasible and small size. The shock performance of the new inertia latch is experimentally verified.

• Journal of the Korea Convergence Society
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• v.11 no.11
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• pp.203-209
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• 2020

A hybrid mount featuring rubber element and piezoelectric actuator is devised to reduce vibration when starting a vehicle engine. As a first step, a passive mount adopting rubber element is manufactured and its dynamic characteristics are experimentally evaluated. After evaluating dynamic characteristics of the manufactured inertial piezoelectric actuator, the proposed hybrid mount is then established by integrating the piezoelectric actuator with the rubber element for performance improvement at non-resonant high frequencies. A mathematical model of the established active vibration control system is formulated and expressed in the state space form. Subsequently, sliding mode controller (SMC) is designed to attenuate the vibration transmitted from the base excitation. Finally, control performances of the proposed hybrid mount are evaluated such as transmissibility in frequency domain and time responses.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.1
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• pp.189-195
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• 2002

This paper deals with the free vibration of horizontally curved beams with transition currie. Based on the dynamic equilibrium equations of a curved beam element subjected to the stress resultants and inertia forces, the governing differential equations are derived for the out-of-plane vibration of curved beam with variable curvature. These equations are applied to the beam having transition curve in which the clothiod curve is chosen in this study. The differential equations are solved by the numerical methods lot calculating the natural frequencies and mode shapes. For verifying theories developed herein, the frequency parameters obtained from this studs and ADINA are compared with each other. As the numerical results, the various parametric studies effecting on natural frequencies are investigated and those results are presented in tables and figures.

• Computational Structural Engineering
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• v.4 no.1
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• pp.20-27
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• 1991

본 논문에서는 유체-구조 상호작용해석의 일종의 3차원 접수구조물의 진동해석을 효과적으로 수행하기 위한 해석방법을 제시하기 위하여 동적재해석기법을 검토하였다. 접수구조물의 유한구조 상호작용해석 결과는 구조진동의 관심 주파수역에서는 3차원 연성 부가수질량으로 표현되는 관성력으로 나타난다. 따라서 구조질량행렬에 부가수질량 행렬이 더해져서 전체 관성력으로 표현된다. 이 부가수질량을 추가질량으로 보고 재해석기법을 응용하는 방법을 수치실험을 통해 검증하였다. 이 때 재해석기법이 갖추어야 할 조건은 원구조의 질량과 거의 같은 정도의 질량이 추가되고 또한 완전 연성질량이 추가된 경우에도 정확한 해를 주어야 한다는 것이다. 이를 검증하기 위해 직접재해석기법과 섭동법을 이용한 재해석기법으로 4질량 스프링지지구조에 대한 해석을 수행한 결과 직접재해석기법의 응용이 적합함을 쉽게 입증할 수 있었다. 접수구조물의 예로는 3차원 잠수주상체에 대해 접수진동해석을 수행하였으며 그 결과 선체진동해석에 전통적으로 이용되고 있는 2차원 부가수질량과 3차원 수정계수를 사용한 기준차수법에서는 수지모드와 수평-비틔 연성모드와 같이 서로 독립적인 모드에 대해서는 따로 진동해석을 수행해 주어야 하는 단점이 발견되었다. 이 단점을 보완한 각 모드의 3차원 수정계수행렬을 이용한 재해석기법을 도입하여 모드에 상관없이 동시에 해를 구할 수 있었다. 그러나, 이 방법은 3차원 수정계수가 구해져 있는 경우에 한해서만 적용가능하며 실제 선체진동의 경우에는 10Hz 미만의 저차 주선체 진동에 한해서만 적용가능한 방법이다. 고차의 진도옴드에는 3차원 수정계수를 구할 수 없기 때문에 유체-구조 상호작용 해석결과로부터 얻은 3차원 연성 부가수질량을 이용하게 되며 이 때 이 행렬이 접수구조 표면의 전 자유도와 연성되어 있기 때문에 방대한 방정식을 푸어야 하지만 직접재해석기법을 적용함으로써 정확한 해를 구할 수 있었다. 또한 3차원 부가수질량을 이용한 직접재해석기법은 종래의 2차원 부가수질량과 3차원 수정계수를 이용한 방법에 비해 해석시간 면에서도 전혀 불리한 점이 없는 경제적 방법임이 밝혀졌다. 앞으로 Slamming 혹은 수중폭파 등의 충격하중에 의한 천이 구조응답 해석을 위한 효과적인 방법에 대해서도 연구결과를 발표할 계획이다.

• Journal of Ocean Engineering and Technology
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• v.15 no.3
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• pp.9-19
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• 2001

In this paper we present the aspect of inertial oscillation typically observed in the spin-up of fluids at low Rossby numbers in a circular cylinder. Numerical computations for the quasi three-dimensional equation as well as one-dimensional equation are performed to estimate the predictability of the one-dimensional equation with Ekman pumping/suction models. It is assumed that the discrepancy between the two results may be attributed to the inertial oscillation The detailed analysis to the numerical results reveals that the axial plane is dominated by a comparatively strong oscillatory flows caused by the inertial oscillation. In view of the fact that the time-averaged flow field however agrees to the Taylor-Proudman theorem, it is recommended that further analysis is needed to obtain an improved one-dimensional model like the Reynolds-averaged Navier-Stokes equation for turbulent flows.