• 한국생산제조학회지
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• 제19권2호
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• pp.267-274
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• 2010

Recently, the magnetorheological (MR) polishing process has been examined as a new ultra-precision polishing technology for mirror surface generation in many applications, such as aspheric lenses, biochips, micro parts, etc. This method uses MR fluids which contains micro abrasives as a polishing media, and can. It is possible to obtain nano level surface roughness under suitable process conditions, however, required polishing time is highly dependent on the applied pre-polishing methods due to its very small material removal rate. Thus, in this study, a combined polishing method is presented to reduce total polishing time for SUS304. First, the electropolishing (EP) method was applied to obtain fine surface roughness, and the MR polishing was followed. Surface roughness variations were investigated according to the process conditions. As the results of this study, it was possible to reduce total polishing time for SUS304 using the proposed combined polishing method.

• 한국생산제조학회지
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• 제19권2호
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• pp.184-190
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• 2010

Recently, the polishing process using magnetorheological fluids(MR fluids) has been focused as a new ultra-precision polishing technology for micro and optical parts such as aspheric lenses, etc. This method uses MR fluid as a polishing media which contains required micro abrasives. In the MR polishing process, the surface roughness and material removal rate of a workpiece are affected by the process parameters, such as the properties of used nonmagnetic abrasives(particle material, size, aspect ratio and density, etc.), rotating wheel speed, imposed magnetic flux density and feed rate, etc. The objective of this research is to predict MRR according to the polishing conditions based on the multiple regression analysis. Three polishing parameters such as wheel speed, feed rates and current value were optimized. For experimental works, an orthogonal array L27(313) was used based on DOE(Design of Experiments), and ANOVA(Analysis of Variance) was carried out. Finally, it was possible to recognize that the sequence of the factors affecting MRR correspond to feed rate, current and wheel speed, and to determine a combination of optimal polishing conditions.

• 유변학
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• 제11권2호
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• pp.73-81
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• 1999

회전식 점도 측정기를 이용하여 상용화된 전기유변(electrorheological, ER)유체와 자기유변(magnetorheological, MR)유체의 특성을 비교하여 이를 이용한 장치 설계시 두 유체 중에 유리한 것을 선택하는데 도움이 되고자 하는 것이 본 논문의 의도이며, 이러한 유체의 특성에서 전단변형률의 변화에 따른 전단응력의 변화, 온도변화에 따른 전단응력의 변화, 작용하는 장의 세기에 따른 전단응력의 변화 등을 비교하였다. 온도의 변화에 따른 유체의 특성 변화는 MR유체가 ER유체보다 적게 받는 경향이 있었다. 두 유체의 응용 예로서 제작된 댐퍼의 경우에 유압 시험기를 이용하여 인장과 압축될 때 장의 On/Off에 따른 시간지연과 감쇄력을 비교하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.480-485
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• 2009

This paper presents dynamic modeling and control analysis of a military vehicle suspension featuring MR valve structure. Firstly, the dynamic model of the suspension system which is included gas spring, MR valve and gas chamber is established with respect to the disturbance. Secondly, the friction model of the suspension system is derived by considering experiment result of the MR suspension system. And then, response characteristics of the damping force with respect to the magnetic field and friction force with the proposed friction model are provided to show the feasibility of practical application. In addition, control performance of the proposed MR suspension system is evaluated with quarter vehicle.

• 한국소음진동공학회논문집
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• 제20권1호
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• pp.58-65
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• 2010

This paper presents dynamic modeling and control analysis of a military vehicle suspension featuring MR valve structure. Firstly, the dynamic model of the suspension system which is included gas spring, MR valve and gas chamber is established with respect to the disturbance. Secondly, the friction model of the suspension system is derived by considering experiment result of the MR suspension system. And then, response characteristics of the damping force with respect to the magnetic field and friction force with the proposed friction model are provided to show the feasibility of practical application. In addition, control performance of the proposed MR suspension system is evaluated with quarter vehicle.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.26-27
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• 2014

This paper proposes a new bed stage system for vibration attenuation in patient compartment of ambulance. The bed stage which consist of four MR dampers can isolate vibration in the vertical, rolling and pitching directions. After evaluating dynamic characteristics of MR damper, 1/4 bed stage model is formulated. The sky hook controller is then utilized for vibration control. Finally, control responses of the bed stage equipped with MR dampers are presented.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.71-76
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• 2010

This paper presents the feasibility for improving the ride quality of railway vehicle equipped with semi-active suspension system using magnetorheological(MR) fluid damper. In order to achieve this goal, a fifteen degree of freedom of railway vehicle model, which includes a car body, bogie frame and wheel-set is proposed to represent lateral, yaw and roll motions. The MR damper system is incorporated with the governing equation of motion of the railway vehicle which includes secondary suspension. To illustrate the effectiveness of the controlled MR dampers on railway vehicle secondary suspension system, the sky-hook control law using the velocity feedback is adopted. Computer simulation for performance evaluation is performed using Matlab. Various control performances are demonstrated under external excitation which is the creep force between wheel and rail.

• Smart Structures and Systems
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• 제12권6호
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• pp.695-705
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• 2013

The purpose of this paper is to identify through experiments the finite element (FE) model of a building structure using a magnetorheological (MR) fluid damper. The FE model based system identification (FEBSI) technique evaluates the control performance of an MR damper that has nonlinear characteristics as equivalent linear properties such as mass, stiffness, and damping. The Bingham and Bouc-Wen models were used for modeling the MR damper and the equivalent damping increased by the MR damper was predicted by applying an equivalent linearization technique. Experimental results indicate that the predicted equivalent damping matches well with the experimentally obtained damping.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.323-330
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• 2004

The purpose of this paper is to experimentally identify the finite element (FE) model of a building structure with magnetorheological (MR) fluid damper. Using FE model based system identification (FEBSI) technique, The model of MR damper having nonlinear characteristics is expressed with equivalent linear properties such as mass, stiffness, and damping. Bingham model is used for MR damper modeling. The equivalent stiffness and damping matrices of MR damper are predicted by applying an equivalent linearization technique, and those values are compared with the experimentally obtained ones.

• Smart Structures and Systems
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• 제1권3호
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• pp.235-256
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• 2005

The non-linear behaviour of electrorheological (ER) and magnetorheological (MR) dampers makes it difficult to design effective control strategies, and as a consequence a wide range of control systems have been proposed in the literature. These previous studies have not always compared the performance to equivalent passive systems, alternative control designs, or idealised active systems. As a result it is often impossible to compare the performance of different smart damper control strategies. This article provides some insight into the relative performance of two MR damper control strategies: on/off control and feedback linearisation. The performance of both strategies is benchmarked against ideal passive, semi-active and fully active damping. The study relies upon a previously developed model of an MR damper, which in this work is validated experimentally under closed-loop conditions with a broadband mechanical excitation. Two vibration isolation case studies are investigated: a single-degree-of-freedom mass-isolator, and a two-degree-of-freedom system that represents a vehicle suspension system. In both cases, a variety of broadband mechanical excitations are used and the results analysed in the frequency domain. It is shown that although on/off control is more straightforward to implement, its performance is worse than the feedback linearisation strategy, and can be extremely sensitive to the excitation conditions.