• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.196-203
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• 1998

Viscoelastic dampers have been successfully applied to building structures for reduction of vibration induced by wind or earthquakes. But accurate estimation of responses of building structures with viscoelastic dampers is very difficult, because the properties of viscoelastic damper is dependent on temperature and frequency of vibration. For efficient control of building vibration, required damping of viscoelastic damping device need be estimated and dynamic analysis method which can estimate the response of building structure with viscoelastic damper system is indispensable. In this paper, an efficient dynamic analysis method of a building structure with viscoelastic dampers is proposed. Efficiency and accuracy of the proposed method are verified comparing analytic results with shaking table test results using reduced building models.

• Smart Structures and Systems
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• 제9권6호
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• pp.549-563
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• 2012

Theoretical analysis is performed on a multi-mode energy harvester design with focus on the first two vibration modes. Based on the analysis, a modification is proposed for designing a novel adaptive multi-mode energy harvester. The device comprises a simply supported beam with distributed mass and piezoelectric elements, and an adaptive damper that provides a 180 degree phase shift for the motions of two supports only at the second vibration mode. Theoretical analysis and numerical simulations show that the new design can efficiently scavenge energy at the first two vibration modes. The energy harvesting capability of the multi-mode energy harvester is also compared with that of a cantilever-based energy harvester for single-mode vibration. The results show that the energy harvesting capacity is affected by the damping ratios of different designs. For fixed damping ratio and design dimensions, the multi-mode design has higher energy harvesting capacity than the cantilever-based design.

• 한국자기공명학회논문지
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• 제23권2호
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• pp.46-50
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• 2019

Spin orbit torque would be applied as the next generation of MRAM, so many researchers are interested in related field. To make a more efficient device, electric current should convert into spin current with high efficiency. Moreover, it becomes important to measure efficiency of spin orbit torque accurately. We measured spin torque FMR of W/CoFeB hetero structure system with direct current. The efficiencies of the damping like torque and field like torque were measured by using the linewidth and on-resonance field proportional to direct current. In addition, we analyzed that a quadratic shift of the on-response field was caused by the Joule heating.

• 드라이브 ㆍ 컨트롤
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• 제15권1호
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• pp.38-49
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• 2018

This research describes the development model and testing of a hybrid damper which can be applicable to a vehicle suspension. The hybrid damper is devised to improve the performance of a conventional passive oil damper using a magneto-rheological (MR) accumulator which consists of a gas accumulator and a MR device. The level of damping is continuously variable by the means of control in the applied current in a MR device fitted to a floating piston which separates the gas and the oil chamber. A simple MR device is used to resist the movement of floating piston. At first a mathematical model which describes all flows within the conventional oil damper is formulated, and then a small MR device is also devised and adopted to a mathematical model to characterize the performance of the device.

• 한국항공우주학회지
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• 제38권9호
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• pp.882-889
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• 2010

수동형 진동제어 방식과 같이 시스템이 안정되며, 수동형에 비해 높은 제진 효과가 기대되는 반능동 진동제어 방식은 시스템의 안정화가 요구되는 우주구조물의 제진방법에 유효한 진동제어 방식중 하나이다. On-Off 제어방식에 근거한 반능동 제어는 On-Off 스위칭 시에 전달력의 불연속성으로 인한 chattering을 발생시킬 수 있으며, 이는 탑재체 구조물의 고유진동수와의 커플링으로 인하여 지향성능을 저하시키는 원인으로 작용할 수 있다. 본 논문에서는 chattering 영향 최소화를 통한 지향성능향상을 목적으로 LQ(Linear Quadratic)이론에 기반한 가변 감쇠형 반능동 제어기법을 제안하였다. 시뮬레이션 결과는 본 논문에서 제안한 반능동 제어기법은 기존의 skyhook와 LQ를 기반으로 하는 Bang-Bang 반능동 제어기법과 비교하여 높은 진동절연 성능을 나타내고 있다.

• 한국정밀공학회지
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• 제3권2호
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• pp.62-75
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• 1986

An experimental investigation of the machining characteristics such as cutt- ing resistance, surface roughness and tool wear in turning the test pieces of SM45C steel with both coated and uncoated carbide tool tips under various cutting conditions was conducted. Also a specially designed simple vibration damping device was experimentally evaluated for its effectiveness on machined surface roughness and a vibration test was conducted to confirm its ability to reduce the amplitude. Based on these tests finding, the following conclusions are made; 1. The cutting resistance($\textrm{p}_{1}$) increases as the depth of cut(d) increases at fixed feed rate(f) over the cutting speed(v) range of 43-226 m/min and p decreses about 18% average when V is increased for fixed d and f. At V= 226m/min, $\textrm{p}_{1}$/for A, C tips are about the same level but $\textrm{p}_{1}$ for B tip is 15% less than A, C tips. 2. The specific cutting resistance(Ks) at V=226 m/min was derived for A, B, C tips respectively and the value of Ks for B rip is about 20% less than A, C tips. 3. The surface roughness(Ra) improves significantly as the cutting speed(V) is increased and this effect was greater when V>100 m/min. On the other hand, Ra deteriorates as the feed rate(f) is increased and this trend was accelerated when f>0.3 mm/rev. With regard to the difference of Ra values among A, B, C tips, at V=226m/min, d=0.4mm, and f=0.31-0.61mm/rev, Ra values for B.C tips are about 17% less than tip A. 4. The experimental tool wear equations were derived for A, B, C tips and from these equations, the tool life($\textrm{T}_{\textrm{L}}$) baced on the I.S.O. criteria was calculated to be $\textrm{T}_{\textrm{L}}$<$\textrm{T}_{\textrm{LB}}$<$\textrm{T}_{\textrm{LC}}$ for both flank wear($\textrm{V}_{\textrm{B}}$) and boundary wear($\textrm{V}_{\textrm{N}}$). Hence, the coated tips are superior to the uncoated tip and tip C is considered to be the best. 5. The cutting resistance may be slightly reduced and the surface rounghness improved when the damper is used especially when V>100 m/min. Therefore this damping device is considered to be effective and practical. The experimental surface roughness equations were also derived. Based on the vibration test, it is established that the surface roughness improvement was the result of amplitude reduction made possible by the damper.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.362-369
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• 2002

This paper mainly propose the new passive vibration control device, named BRV(the bridge reduced vibration), for reducing excessive traffic-induced vibration of bridges and for measuring performance of BRV numerical example was simulated. The purpose of BRV is mainly on reducing vertical acceleration and displacement of bridge. In BRV we can control the stiffness and damping coefficient to accept the performance we want. The result of simulation showed that the vertical acceleration and displacement was effectively diminished. It would be concluded that BRV can be used to improve the serviceability of bridge and fatigue life etc.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.596-601
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• 1998

Rubber has been widely used as a good device for reducing the vibration in various fields including the anti seismic device like LRB. The damping characteristic is needed to be mathematically modeled to predict the dynamic behavior of the isolated system. In this paper, The frequency response function was obtained experimentally by the resonant method and simulation was performed with the hysteretic model using the resonant test result. the hysteretic behavior of the rubber can be explained by the change of the static stiffness obtained in the DC by the concept of the transfer function.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1060-1063
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• 1996

Remote Cask Grappling and Lid Unbolting Device (RCGLUD) is developed as a dedicated device capable of performing complete procedure of handling nuclear spent fuel transport cask. Since RCGLUD is suspended to an overhead crane, its body should undergo prolonged vibration upon actuation in rotational direction and it becomes difficult to achieve precise grappling of the cask. Therefore, this paper presents an adaptation of input shaping technique to effectively suppress the rotational vibration of RCGLUD and achieve precise positioning in rotational direction. This technique has a practical merit in that it requires only the information on the system natural frequency and the damping ratio. Its performance is verified by both simulation and experimental studies, and revealed that the method is also insensitive to modeling error.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권4호
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• pp.213-219
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• 2000

In this paper, a controller design method is proposed for haptic interface considering transparency and robust stability. For this, a performance index for the transparency as performance measure is defined in the points of impedance matching and the optimal solution which is minimizing the performance index is obtained by solving H2 optimal problem. In haptic interface, the modeling uncertainties can be restricted to that of haptic device. To implement the robust stabilizing haptic controller to the uncertainties of haptic device, a robust stable condition using H$\infty$ norm from small gain theorem is proposed. To verify the effectiveness of the proposed haptic controller design scheme, numerical examples and experimental results are illustrated for virtual wall consisting of stiffness and damping factor.