• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.329-334
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• 2002

Preliminary test for the design and construction of a tuned dynamic absorber is a conducted. Proposed tuned dynamic absorber is a cantilevered beam type, and is supposed to adjust its natural frequency according to the changing operation condition of the primary system. The modal mass of the dynamic absorber is the easiest to control, therefore, the position of the attached mass of the dynamic absorber is considered as the main design parameter of the absorber. The effect of the dynamic absorber is experimentally verified under various operation conditions of the primary system.

• Smart Structures and Systems
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• v.5 no.5
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• pp.517-529
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• 2009

This paper presents the development of a new Adaptive Tuned Dynamic Vibration Absorber (ATDVA) working with magnetorheological elastomers (MREs). The MRE materials were fabricated by mixing carbonyl iron particles with silicone rubber and cured under a strong magnetic field. An ATDVA prototype using MRE as an adaptable spring was designed and manufactured. The MRE ATDVA worked in a shear mode and the magnetic field was generated by a magnetic circuit and controlled through a DC power supply. The dynamic performances or the system transmissibility at various magnetic fields of the absorber were measured by using a vibration testing system. Experimental results indicated that this absorber can change its natural frequency from 35Hz to 90Hz, 150% of its basic natural frequency. A real time control logic is proposed to evaluate the control effect. The simulation results indicate that the control effect of MRE ATDVA can be improved significantly.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.159-163
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• 2005

A dynamic vibration absorber using the Zener's model has been taken into account with respect to frequency response characteristics. The concept of the tuned mass damper with a single degree of freedom has been well applied for many industrial fields, because many researchers have extensively studied various basic characteristics, performance and optimization methods for long time. The Zener's model has an additional spring, which is connected between a damper and a mass, while the tuned mass damper with a single degree of freedom consists of a mass, a spring and a damper connected in parallel. In previous works, the basic performance and characteristics of the Zoner's model as a dynamic vibration absorber have not been investigated. In this study, the frequency response characteristics according to the parameter change of the Zener's model have been described. In order to find the optimum value of several parameters, we use iterative scheme with three dimensional frequency response diagram by MATLAB programming. Present results shows the Zener's model can give more good damping performance than the simple tuned mass damper, and the numerical of optimization method should be developed for the efficient vibration absorbtion.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.111.4-111
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• 2001

In this paper, an adaptively tuned dynamic absorber is proposed. The adaptively tuned dynamic absorber is a dynamic absorber whose stiffness is tuned so that the natural frequency of the absorber coincides with the operating or natural frequency estimated by an adaptive algorithm. The feature of this absorber is as follows. It has an electrodynamic device for the stiffness control. Using Lorenz´s force, it changes the stiffness by changing the applied current. The change of stiffness results in the natural frequency shift, because its mass and damping coefficient are fixed. We may reduce the vibration of the overall system by tuning the natural frequency of the dynamic absorber to the resonant frequency of the structure, when the dominant single tone oscilation occurs in the system ...

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.605-609
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• 2010

In modern surveillance equipment, infrared (IR) sensors are essential for detection and observation. The IR sensor is connected to a miniature cryogenic cooler to maintain the temperature at very low levels, i.e., temperatures as low as 77 K. However, the quality of the image captured by the sensor is degraded by the transmission of vibration disturbances from the cooler. Therefore, to maintain high image quality, the compressor vibration and the force transmitted to the sensor have to be mitigated. For the compressor vibration isolating system, a tuned dynamic vibration absorber, combined with a passive isolator, is proposed. A cryogenic compressor bracket and springs are designed to allow the absorber mass to mitigate the vibration jitter in the axial direction. The system design is analyzed and evaluated in terms of the dynamic suppression of the harmonic force at the operating frequency of the cooler.

• Wind and Structures
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• v.7 no.4
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• pp.215-234
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• 2004

The tuned liquid damper (TLD) is increasingly being used as an economical and effective vibration absorber. It consists of a water tank having the fundamental sloshing fluid frequency tuned to the natural frequency of the structure. In order to perform efficiently, the TLD must possess a certain amount of inherent damping. This can be achieved by placing screens inside the tank. The current study experimentally investigates the behaviour of a TLD equipped with damping screens. A series of shake table tests are conducted in order to assess the effect of the screens on the free surface motion, the base shear forces and the amount of energy dissipated. The variation of these parameters with the level of excitation is also studied. Finally, an amplitude dependent equivalent tuned mass damper (TMD), representing the TLD, is determined based on the experimental results. The dynamic characteristics of this equivalent TMD, in terms of mass, stiffness and damping parameters are determined by energy equivalence. The above parameters are expressed in terms of the base excitation amplitude. The parameters are compared to those obtained using linear small amplitude wave theory. The validity of this nonlinear model is examined in the companion paper.

• International Journal of High-Rise Buildings
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• v.10 no.2
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• pp.85-92
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• 2021

Dynamic vibration absorbers (DVAs) in the form of tuned sloshing dampers (TSDs) and tuned mass dampers (TMDs) are commonly used to reduce the wind-induced motion of high-rise buildings. Full-scale performance of structure-DVA systems must be evaluated during the DVA commissioning process using structural monitoring data. While the random decrement technique (RDT) is sometimes employed to evaluate the DVA performance, it is shown to have no theoretical justification for application to structure-DVA systems, and to produce erroneous results. Subsequently, several practical methods with a sound theoretical basis are presented and illustrated using simulated and real-world data. By monitoring the responses of the structure and DVA simultaneously, it is possible to directly measure the effective damping of the system or perform system identification from which the DVA performance can be evaluated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.8 s.239
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• pp.1093-1101
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• 2005

Hybrid mass damper systems have recently been introduced as a dynamic vibration absorber to exploit the benefits of both the conventional tuned mass damper system and the active control system. A hybrid system is programmed to function as either a conventional TMD or as an active system according to the wind conditions and the resultant building and damper mass vibration characteristics. This paper deals with the design of the robust controller for the control of the flexible box structure. The control algorithm was devised based on $H_2$(LQG) robust control logic with acceleration feedback and to improve the capability of the controller Kalman Filter was accepted for the system. To test the ability of the robust controller using the linear motor damper system, performance tests and simulations were carried out on the full-scale steel frame structure. Through the performance tests, it was confirmed that acceleration levels are reduced down.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.119-124
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• 2009

This paper proposes a tuned liquid column sloshing damper(TLCSD) and presents experimental results to evaluate its control performance. The proposed damper acts as a tuned liquid column damper(TLCD) and a tuned liquid damper(TLD), respectively, in both principal axes of building structures. Shaking table test was performed to grasp its dynamic characteristics. Testing results showed that under inclined incident excitations, a TLCSD used in this study have dynamic characteristics coupled by both TLCD and TLD.

• Journal of Aerospace System Engineering
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• v.4 no.4
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• pp.28-36
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• 2010

Current tanks have been developed to increase mobility and firepower, and its maximum range and destructive power are improved. This great change causes remained vibration of a gun barrel after firing. For this reason, people are trying to control vibration of gun barrel effectively. This thesis presents a modeling method and analysis results for gun barrel by using a thermal shroud as an absorber mass. DTS(Dynamically Tuned Shroud) is a vibration damping system using a thermal shroud as an added mass for decreasing remained vibration. The model has an advantage that the gun barrel's vibration can be decreased by dissipating a kinetic energy of thermal shroud without install an additional dynamic absorber to tip of the gun barrel. For analyzing the damping performance of the DTS, We derived an equation of motion of the barrel after setting a mathematical modeling, and found out the frequency analysis and tendency according to stiffness ratio between barrel and shroud.