• Title/Summary/Keyword: Isolation System

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Seismic response of spring-damper-rolling systems with concave friction distribution

  • Wei, Biao;Wang, Peng;He, Xuhui;Jiang, Lizhong
    • Earthquakes and Structures
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    • v.11 no.1
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    • pp.25-43
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    • 2016
  • The uneven distribution of rolling friction coefficient may lead to great uncertainty in the structural seismic isolation performance. This paper attempts to improve the isolation performance of a spring-damper-rolling isolation system by artificially making the uneven friction distribution to be concave. The rolling friction coefficient gradually increases when the isolator rolls away from the original position during an earthquake. After the spring-damper-rolling isolation system under different ground motions was calculated by a numerical analysis method, the system obtained more regular results than that of random uneven friction distributions. Results shows that the concave friction distribution can not only dissipate the earthquake energy, but also change the structural natural period. These functions improve the seismic isolation efficiency of the spring-damper-rolling isolation system in comparison with the random uneven distribution of rolling friction coefficient, and always lead to a relatively acceptable isolation state even if the actual earthquake significantly differs from the design earthquake.

A Study on Active Vibration Isolation Using Electro-Magnetic Actuator (전자기력을 이용한 능동제진에 관한 연구)

  • 손태규;김규용;박영필
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.5
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    • pp.1169-1181
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    • 1994
  • Vibration isolation of mechanical systems, in general, is achieved through passive or active vibration isolators. Passive vibration isolator has an inherenrt performance limitation. Whereas, active vibration isolator provides significantly superior vibration-isolation performance at the cost of energy sources and sensors. Recently, in many cases, such as suspension system, precision machinery ... etc, active isolation system outweighs its limitation. Therefore, many studies, researches, and applications are carried out in this field. In this study, vibration-isolation characteristics of an active vibration control system using electromagnetic force actuator are investigated. Several control algorithms including optimal, feedforward are used for active vibration isolation. From the experimental results of each algorithm, effective control algorithms for this active vibration-isolation system are proposed.

Frequency-shaped Sliding Mode Control of Isolation Table Equipped with Precision devices (정밀기기가 탑재된 방진대의 주파수성형 슬라이딩모드 제어)

  • 김효준;박영필
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.2
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    • pp.124-131
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    • 2002
  • This paper presents the design of an active vibration suppression controller for an air-spring type vibration isolation table. Firstly, isolation system model is constructed considering the isolation table, attached equipment and voice-coil actuator. An active control system is designed based on frequency-shaped sliding mode control theory rewarding high frequency uncertainties with respect to attached equipments on the isolation table. Finally. the performance of the active isolation system is evaluated by simulation under some disturbance conditions which are transmitted from base structure of the isolation system.

Multi-objective Fuzzy Control of a Spacial Structure using Smart Base Isolation System (스마트 면진시스템을 이용한 대공간 구조물의 다목적 퍼지제어)

  • Kang, Joo-Won;Kim, Hyun-Su;Lim, Jun-Ho
    • Journal of Korean Association for Spatial Structures
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    • v.11 no.2
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    • pp.89-99
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    • 2011
  • In this study, a smart base isolation system has been proposed to reduce dynamic responses of a spacial structure subjected to seismic excitation. MR dampers and low damping elastomeric bearings were used to compose a smart base isolation system and its vibration control performance has been investigated compared to that of the optimally designed lead-rubber bearing (LRB) isolation system. Control performance of smart base isolation system depends on control algorithm. Fuzzy controller was used in this study to effectively control the spacial structure having a smart base isolation system. Dynamic responses of the spacial structure with isolation system is conflict with base drifts and thus these two responses are selected as objective functions to apply multi-objective genetic algorithm to optimization of fuzzy controller. Based on numerical simulation results, it has been shown that the smart base isolation system proposed in this study can drastically reduce base drifts and seismic responses of the example spacial structure in comparison with the optimally designed LRB isolation system.

Dynamic Characteristics of the Vibration Isolation System for High Precision Processing Machinery (정밀가공장비용 면진시스템의 동특성)

  • 김영중;김병현
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.1115-1121
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    • 2003
  • The vibration isolation table system for the high precision Processing machinery has been developed. The system uses air spring as its isolation elements. An investigation of the model and the test results showed that the diaphragm has a role in the mathematical model. The vibration levels at various floors in the laboratory were investigated during operating the large shaking table for the selection of optimum installation location. The vibration test on the designed system showed good isolation performances.

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Modeling and Control of a Four Mount Active Micro-vibration Isolation System

  • Banik, Rahul;Gweon, Dae-Gab
    • Journal of the Semiconductor & Display Technology
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    • v.5 no.4 s.17
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    • pp.41-45
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    • 2006
  • Micro vibration isolation, typically originated from ground, is always a prime concern for the nano-measurement instruments such as Atomic Force Microscopes. A four mount active vibration isolation system is proposed in this paper. Modeling and control of such a four mount system was analyzed. Combined active-passive isolation principle is used for vibration isolation by mounting the instrument on a passively damped isolation system made of Elastomer along with the active stage in parallel that consists of very soft actuation system, the Voice Coil Motor. The active stage works in combination with the passive stage for working as a very low frequency vibration attenuator.

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A feasibility study on smart base isolation systems using magneto-rheological elastomers

  • Koo, Jeong-Hoi;Jang, Dong-Doo;Usman, Muhammad;Jung, Hyung-Jo
    • Structural Engineering and Mechanics
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    • v.32 no.6
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    • pp.755-770
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    • 2009
  • This study proposes a new smart base isolation system that employs Magneto-Rheological Elastomers (MREs), a class of smart materials whose elastic modulus or stiffness can be varied depending on the magnitude of an applied magnetic field. It also evaluates the dynamic performance of the MRE-based isolation system in reducing vibrations in structures subject to various seismic excitations. As controllable stiffness elements, MREs can increase the dynamic control bandwidth of the isolation system, improving its vibration reduction capability. To study the effectiveness of the MRE-based isolation system, this paper compares its dynamic performance in reducing vibration responses of a base-isolated single-story structure (i.e., 2DOF) with that of a conventional base-isolation system. Moreover, two control algorithms (linear quadratic regulator (LQR)-based control and state-switched control) are considered for regulating the stiffness of MREs. The simulation results show that the MRE-based isolation system outperformed the conventional system in suppressing the maximum base drift, acceleration, and displacement of the structure.

Lyapunov-based Semi-active Control of Adaptive Base Isolation System employing Magnetorheological Elastomer base isolators

  • Chen, Xi;Li, Jianchun;Li, Yancheng;Gu, Xiaoyu
    • Earthquakes and Structures
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    • v.11 no.6
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    • pp.1077-1099
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    • 2016
  • One of the main shortcomings in the current passive base isolation system is lack of adaptability. The recent research and development of a novel adaptive seismic isolator based on magnetorheological elastomer (MRE) material has created an opportunity to add adaptability to base isolation systems for civil structures. The new MRE based base isolator is able to significantly alter its shear modulus or lateral stiffness with the applied magnetic field or electric current, which makes it a competitive candidate to develop an adaptive base isolation system. This paper aims at exploring suitable control algorithms for such adaptive base isolation system by developing a close-loop semi-active control system for a building structure equipped with MRE base isolators. The MRE base isolator is simulated by a numerical model derived from experimental characterization based on the Bouc-Wen Model, which is able to describe the force-displacement response of the device accurately. The parameters of Bouc-Wen Model such as the stiffness and the damping coefficients are described as functions of the applied current. The state-space model is built by analyzing the dynamic property of the structure embedded with MRE base isolators. A Lyapunov-based controller is designed to adaptively vary the current applied to MRE base isolator to suppress the quake-induced vibrations. The proposed control method is applied to a widely used benchmark base-isolated structure by numerical simulation. The performance of the adaptive base isolation system was evaluated through comparison with optimal passive base isolation system and a passive base isolation system with optimized base shear. It is concluded that the adaptive base isolation system with proposed Lyapunov-based semi-active control surpasses the performance of other two passive systems in protecting the civil structures under seismic events.

Seismic isolation performance sensitivity to potential deviations from design values

  • Alhan, Cenk;Hisman, Kemal
    • Smart Structures and Systems
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    • v.18 no.2
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    • pp.293-315
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    • 2016
  • Seismic isolation is often used in protecting mission-critical structures including hospitals, data centers, telecommunication buildings, etc. Such structures typically house vibration-sensitive equipment which has to provide continued service but may fail in case sustained accelerations during earthquakes exceed threshold limit values. Thus, peak floor acceleration is one of the two main parameters that control the design of such structures while the other one is peak base displacement since the overall safety of the structure depends on the safety of the isolation system. And in case peak base displacement exceeds the design base displacement during an earthquake, rupture and/or buckling of isolators as well as bumping against stops around the seismic gap may occur. Therefore, obtaining accurate peak floor accelerations and peak base displacement is vital. However, although nominal design values for isolation system and superstructure parameters are calculated in order to meet target peak design base displacement and peak floor accelerations, their actual values may potentially deviate from these nominal design values. In this study, the sensitivity of the seismic performance of structures equipped with linear and nonlinear seismic isolation systems to the aforementioned potential deviations is assessed in the context of a benchmark shear building under different earthquake records with near-fault and far-fault characteristics. The results put forth the degree of sensitivity of peak top floor acceleration and peak base displacement to superstructure parameters including mass, stiffness, and damping and isolation system parameters including stiffness, damping, yield strength, yield displacement, and post-yield to pre-yield stiffness ratio.

A Method to Improve Isolation for Passive RFID Applications (수동형 RFID 시스템 적용을 위한 Isolation 개선 방법)

  • Kim, Jae-Kwon;Burm, Jin-Wook
    • Journal of the Institute of Electronics Engineers of Korea CI
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    • v.44 no.4 s.316
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    • pp.45-49
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    • 2007
  • The isolation between transmitter and receiver has been a critical problem in a pulse-modulated RFID (Radio Frequency Identification) system where transmitter and receiver use the identical frequency. A method using a switch, a mixer, a BPF (band-pass filter), and an additional oscillator in the transmitter is proposed to improve the isolation between transmitter and receiver in an RFID system. The Proposed system up-converts the outgoing wave from a frequency different from the received signal and improves the isolation. The proposed method provided additional 20 dB improvement on the isolation.