• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.3
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• pp.243-250
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• 2002

Semi-active control devices have received significant attention in recent Years because they offer the adaptability of active-control devices without requiring the associated large power sources. Magnetorheological(MR) dampers are semiactive control devices that use MR fluids to produce controllable dampers. This paper applies sliding mode control method using target variation rate of Lyapunov function for the control of structures by use of MR dampers. The three-story building model under earthquake excitation is analyzed by installing a MR damper in the first-story. The performance of semi-active controllers designed by clipped-optimal algorithm and modified sliding mode control algorithm is compared to the performance of passive-type MR dampers. The results indicate that semi-active controllers achieve a greater reduction of responses than passive-type system and especially the controller by modified sliding mode control method shows a good applicability in the view of response control and control force.

• Smart Structures and Systems
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• v.1 no.3
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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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3567-3573
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• 2009

This research proposed a dashpot type mount design using MR fluids, and investigated experimentally the influence of the design parameters of the dashpot MR fluid mount, which affect the damping forces of the dashpot MR fluid mount. In order to observe the influence, the dashpot MR fluid mount which have the different effective length and the core structure is manufactured. The variations of the resistance forces according to different effective lengths of the magnetic pole of MR fluid mount, along which magnetic field is defined, was investigated. It was founded that the resistance forces from the MR mount decreased with increased input frequencies, while increased with increased applied electric current intensities. Nevertheless, there is no appreciable change in the resistance forces with respect to the effective length variations of the magnetic pole of MR fluid mount.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.5
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• pp.85-90
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• 2017

Mica-glass ceramics has features such as micro-sized crystals, high strength, chemical resistance, semitransparent optical properties, etc. Due to its superior material properties, mica glass ceramics have increasing applications in dental and medical components, insulation boards, chemical devices, etc. In many applications, especially for dental and medical components, ultra-precise polishing is required. However, it is known to be a very difficult-to-grind material because of its high hardness and brittle properties. Thus, in this study, a newly developed ultra-precise polishing method is applied to obtain nano-level surface roughness of the mica glass ceramics using magnetorheological (MR) fluids and nano abrasives. Nano-sized ceria particles were used for the polishing of the mica glass ceramics. A series of experiments were performed under various polishing conditions, and the results were analyzed. A very fine surface roughness of Ra=6.127 nm could be obtained.