• Smart Structures and Systems
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• v.14 no.5
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• pp.901-916
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• 2014

Magnetorheological (MR) fluid is one of the field-responsive fluids that is of interest to many researchers due to its high yield stress value, which depends on the magnetic field strength. Similar to electrorheological (ER) fluid, the combination of working modes is one of the techniques to increase the performance of the fluids with limited focus on MR fluids. In this paper, a novel MR testing cell incorporated with valve, shear and squeeze operational modes is designed and constructed in order to investigate the behaviour of MR fluid in combined mode. The magnetic field distribution in the design concept was analyzed using finite element method in order to verify the effective areas of each mode have the acceptable range of flux density. The annular gap of valve and shear were fixed at 1 mm, while the squeeze gap between the parallel circular surfaces was varied up to 20 mm. Three different coil configurations, which were made up from 23 SWG copper wires were set up in the MR cell. The simulation results indicated that the magnetic field distributed in the squeeze gap was the highest among the other gaps with all coils were subjected to a constant applied current of 1 A. Moreover, the magnetic flux densities in all gaps were in a good range of magnitude based on the simulations that validated the proposed design concept. Hence, the 3D model of the MR testing cell was designed using Solidworks for manufacturing processes.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.17-24
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• 2011

It is reported that an intermittently rotating chamber system will improve the ratio of firepower to armament space in the case of mid-calibre automatic guns. However, the parallel index, which is a main component of the system, tends to be torsionally flexible due to the low lateral stiffness of cam followers on the index turret. This may cause the shaft system connecting the turret with the chamber prone to considerable residual torsional vibration so that serious misalignment problems occur during ammunition loading and firing processes. Herein, an electrorhelogical (ER) fluid actuator that can suppress such vibrations and the associated semiactive control algorithm are proposed. By mathematical modeling and computer simulations, the performance of the entire system is proved satisfactory.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.9
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• pp.45-52
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• 2001

This paper presents two different models of electrorheological(ER) valves which can be applicable to an automatic cargo handling system at the seaport. Four different ER fluids, which are commercially available, are adopted and their Bingham characteristics are experimentally evaluated with respect to the intensity of electric field. The field-dependent Bingham models are used in the design of two types of ER valves; single-type and divided-type. The governing equations of motion of the ER valves are derived and the principal design parameters are determined based on 200ton platform to be vertically controlled by the ER valves. Both pressure drops due to the applied field and current density required to operate the ER valves are analyzed. In addition, the pressure drops of the cylinder system are evaluated for both ER valves.

• 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.