• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.200-207
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• 2001

The transmission of harmonic vibratory power form a vibrating rigid body into a supporting plate through passive and active isolators is investigated theoretically and experimentally. The theoretical model allows for the transmission of vertical and horizontal harmonic forces and moments about all three coordinate sun. The experiment is to use vibration actuators attached to the intermediate mass of the two-stage mount to minimize the rotational and translational vibration of the intermediate mass. The performance is done by measuring the vibration at the error sensors due to the primary vibration source and measuring the transfer functions from the control sources to the error sensors. Results show that over a frequence range from 1 to 100Hz, transmission into the supporting plate can be reduced substantially by employing in parallel with existing passive isolators, active isolators adjusted to provide appropriate control force amplitudes.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.63-76
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• 2004

This paper presents LRB-based hybrid base isolation systems employing additional active/semiactive control devices for mitigating earthquake-induced vibration of a cable-stayed 29 bridge. Hybrid base isolation systems could improve the control performance compared with the passive type-base isolation system such as LRB-installed bridge system due to multiple control devices are operating. In this paper, the additional response reduction by the two typical additional control devices, such as active type hydraulic actuators controlled by LQG algorithm and semiactive-type magnetorheological dampers controlled by clipped-optimal algorithm, have been evaluated bypreliminarily investigating the slightly modified version of the ASCE phase I benchmark cable-stayed bridge problem (i.e., the installation of LRBs to the nominal cable-stayed bridge model of the problem). It shows from the numerical simulation results that all the LRB based hybrid seismic isolation systems considered are quite effective to mitigate the structural responses. In addition, the numerical results demonstrate that the LRB based hybrid seismic isolation systems employing MR dampers have the robustness to some degree of the stiffness uncertainty of in the structure, whereas the hybrid system employing hydraulic actuators does not. Therefore, the feasibility of the hybrid base isolation systems employing semiactive additional control devices could be more appropriate in realfor full-scale civil infrastructure applications is clearly verified due to their efficacy and robustness.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.504-507
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• 2005

This paper presents a self-levelling system for a mass, which undergoes a severe acceleration, with integrated displacement feedback control. After a general description of such a system, theoretical analysis is investigated to design an active control device. That is, the self levelling system is used to reduce the 'static' deflections while isolating the 'dynamic' vibration. A computer simulation model of 45 kg with two air spring mounts is considered to predict the performance of the control system. The results showed the controller can reduce the mass's displacement to the level of 1/3-1/5. Thus the self-levelling system can be applied usefully to reduce the dispalcement of a mass which experiences a high g dynamics.

• The Korean Journal of Rheology
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• v.11 no.2
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• pp.112-121
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• 1999

An MR(Magneto-Rheological) fluids damper is designed and applied to vibration suppression of a 1/4 car model. The damping constant of MR damper changes according to input current which is controlled in a semi-active way. Several control algorithms are compared in simulations and experiments. The advantage of the proposed Frequency shaped LQ control is that passenger comfort is emphasized in the range of 4~8Hz and driving safety is emphasized around the resonance frequency of unsprung mass.