• Structural Engineering and Mechanics
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• v.14 no.5
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• pp.521-542
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• 2002

Application of piezoceramic materials in actuation and sensing of vibration is of current interest. Potential and more popular applications of piezoceramics are probably in the field of active vibration control. However, the objective of this work is to investigate the effect of shunted piezoceramics as passive vibration control devices when bonded to a host structure. Resistive shunting of a piezoceramic bonded to a cantilevered duralumin beam has been investigated. The piezoceramic is connected in parallel to an electrical network comprising of resistors and inductors. The piezoceramic is a capacitor that stores and discharges electrical energy that is transformed from the mechanical motion of the structure to which it is bonded. A resistor across the piezoceramic would be termed as a resistively shunted piezoceramic. Similarly, an inductor across the piezoceramic is termed as a resonantly shunted piezoceramic. In this study, the effect of resistive shunting on the nature of damping enhancement to the host structure has been investigated. Analytical studies are presented along with experimental results.

• Journal of the Semiconductor & Display Technology
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• v.6 no.4
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• pp.17-22
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• 2007

Vibration isolation equipments are mostly required in precise measurement and manufacturing system. Among all the vibration isolation equipments, air-spring is the most widely used equipment because of low resonant frequency and high damping ratio. In this study, we used Takagi-Sugeno fuzzy method to design an active vibration isolation system using air-spring, and compared the fuzzy method with passive control method and PID control method. Due to the non-linearity characteristics of air-spring, fuzzy controller was verified to be the most effective both in simulation and experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.291-298
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• 2000

This paper describes a theoretical and experimental investigation into an active vibration isolation system in which four electromagnetic actuators are installed in parallel with each of four passive mounts placed between a piece of equipment and a vibrating base structure. Decentralised velocity feedback control is employed, where each actuator is operated independently by feeding back the absolute equipment velocity at the same location. Although one end of each actuator acts at the sensor positions on the equipment, the control system is not collocated because of the reactive forces acting on the flexible base structure, whose dynamics are strongly coupled with the mounted equipment. Isolation of low frequency vibration is considered where the equipment can be modelled as a rigid body and the mounts as lumped parameter springs and dampers. Control mechanisms are discussed, and some experimental and simulation results are reported.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.1 s.118
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• pp.72-79
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• 2007

As environmental vibration requirements on precision equipment become more stringent, use of pneumatic isolators has become more popular and their performance is subsequently required to be further improved. Dynamic performance of passive pneumatic isolators is related to various design parameters in a complicated manner and, hence, is very limited especially in low frequency range by volume of chambers. In this study, an active control technique, so called time delay control which is considered to be adequate for a low frequency or nonlinear system, is applied to a single chamber pneumatic isolator. The procedure of applying the tine delay control law to the pneumatic isolator is presented and its effectiveness in enhancement of transmissibility performance is shown based on simulation and experiment. Comparison between passive and active pneumatic isolators is also presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.909-914
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• 2006

Vibration isolation tables are mostly required in precise measurement and manufacturing system. Among the vibration isolation tables, an air spring is the most favorable equipment because of low resonant frequency and high damping ratio. However, it is difficult to design the air spring with the required stiffness and damping ratio. Futhermore, whenever conventional active control methods are applied to the air spring, it may be difficult to obtain effective control performance due to high nonlinearity of air spring. In this paper, the optimal design of the air spring is performed using genetic algorithm to bring out low resonant frequency and high damping ratio. Also, active control of the vibration isolation table with 3-DOF model is proposed using the adaptive control method. Through experiments, optimal design is shown to be effective. And performance of the proposed control method is verified to be better than those of the passive control method and the conventional active control methods.

• Smart Structures and Systems
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• v.19 no.1
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• pp.21-31
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• 2017

To control the stochastic vibration of a vibration-sensitive instrument supported on a beam, the beam is designed as a sandwich structure with magneto-rheological visco-elastomer (MRVE) core. The MRVE has dynamic properties such as stiffness and damping adjustable by applied magnetic fields. To achieve better vibration control effectiveness, the optimal bounded parametric control for the MRVE sandwich beam with supported mass under stochastic and deterministic support motion excitations is proposed, and the stochastic and shock vibration suppression capability of the optimally controlled beam with multi-mode coupling is studied. The dynamic behavior of MRVE core is described by the visco-elastic Kelvin-Voigt model with a controllable parameter dependent on applied magnetic fields, and the parameter is considered as an active bounded control. The partial differential equations for horizontal and vertical coupling motions of the sandwich beam are obtained and converted into the multi-mode coupling vibration equations with the bounded nonlinear parametric control according to the Galerkin method. The vibration equations and corresponding performance index construct the optimal bounded parametric control problem. Then the dynamical programming equation for the control problem is derived based on the dynamical programming principle. The optimal bounded parametric control law is obtained by solving the programming equation with the bounded control constraint. The controlled vibration responses of the MRVE sandwich beam under stochastic and shock excitations are obtained by substituting the optimal bounded control into the vibration equations and solving them. The further remarkable vibration suppression capability of the optimal bounded control compared with the passive control and the influence of the control parameters on the stochastic vibration suppression effectiveness are illustrated with numerical results. The proposed optimal bounded parametric control strategy is applicable to smart visco-elastic composite structures under deterministic and stochastic excitations for improving vibration control effectiveness.

• Smart Structures and Systems
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• v.18 no.5
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• pp.955-982
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• 2016

Recent studies integrating vibration control and structural health monitoring (SHM) use control devices and control algorithms to enable system identification and damage detection. In this study real-time SHM is used to enhance structural vibration control and reduce damage. A newly proposed control algorithm, including integrated real-time SHM and semi-active control strategy, is presented to mitigate both damage and seismic response of the main structure under strong seismic ground motion. The semi-active independently variable stiffness (SAIVS) device is used as semi-active control device in this investigation. The proper stiffness of SAIVS device is obtained using a new developed semi-active control algorithm based on real-time damage tracking of structure by damage detection algorithm based on identified system Markov parameters (DDA/ISMP) method. A three bay five story steel braced frame structure, which is equipped with one SAIVS device at each story, is employed to illustrate the efficiency of the proposed algorithm. The obtained results show that the proposed control algorithm could significantly decrease damage in most parts of the structure. Also, the dynamic response of the structure is effectively reduced by using the proposed control algorithm during four strong earthquakes. In comparison to passive on and off cases, the results demonstrate that the performance of the proposed control algorithm in decreasing both damage and dynamic responses of structure is significantly enhanced than the passive cases. Furthermore, from the energy consumption point of view the maximum and the cumulative control force in the proposed control algorithm is less than the passive-on case, considerably.

• Smart Structures and Systems
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• v.16 no.6
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• pp.1003-1021
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• 2015

MR dampers have been proposed for the control of cable vibration of cable-stayed bridge in recent years due to their high performance and low energy consumption. However, the highly nonlinear feature of MR dampers makes them difficult to be designed with efficient semi-active control algorithms. Simulation study has previously been carried out on the cable-MR damper system using a semi-active control algorithm derived based on the universal design curve of dampers and a bilinear mechanical model of the MR damper. This paper aims to verify the effectiveness of the MR damper for mitigating cable vibration through a full-scale experimental test, using the same semi-active control strategy as in the simulation study. A long stay cable fabricated for a real bridge was set-up with the MR damper installed. The cable was excited under both free and forced vibrations. Different test scenarios were considered where the MR damper was tuned as passive damper with minimum or maximum input current, or the input current of the damper was changed according to the proposed semi-active control algorithm. The effectiveness of the MR damper for controlling the cable vibration was assessed through computing the damping ratio of the cable for free vibration and the root mean square value of acceleration of the cable for forced vibration.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.55-62
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• 2004

In general, control performance of the active control system is superior to that of the passive control devices. However, the active system require a large amount of external energy to operate the actuators. Semi-active control systems maintain the reliability of the passive control systems while taking advantage of the adjustability of the active control system. In this research, a semi-active orificed fluid damper having the capacity of about 2 tons was designed and fabricated. It is a two-stage damper with normally open solenoid valve. A series of tests was performed to grasp its performance characteristics. It was also applied to a 6-story steel structure subjected to random and seismic excitations for the confirmation of its validity on structural vibration absorption.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.134-137
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• 2014

The noise reduction performance of a passive facility is dependent on the its length or volume. In other words, this means that the larger the size of passive facility is, the better the noise reduction performance is. The sound directivity control has been proposed as an alternative for the noise reduction without a passive facility. The purpose of this study is to investigate the correlation between the flange attached to inclined exit of the tube and sound directivity when the sound radiates from the tube to the outside. As a result, the sound radiated from flanged tube had weak sound directivity in the wide angle. Also as the flange was bigger, the sound pressure level was lower in the behind the flange.