• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.4
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• pp.377-382
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• 2012

This paper presents a proof-of-concept study on the evaluation of torsional vibration isolation performance through in-situ output torque measurement by using a non-contacting magneto-elastic torque transducer installed in the vehicle driveline system. The de-trending processing is first conducted to extract the torsional vibration from the measured driveline output torque. In order to estimate the transmissibility, primary performance indicator of a vibration isolator, the magnitude of transmitted torsional vibration with different frequencies is compared. From the conservative estimation results, the torsional damper built in a lock-up clutch of a torque converter is identified to be a vibration isolator. The evaluation results show that the fluid damping by torque converter outperforms the vibration isolation function of a torsional damper, and the isolation performance needs to be enhanced.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.35-36
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• 2006

This study is mainly concerned with vibration control of L-type reciprocating air compressor by a dynamic vibration absorber. The dynamic vibration absorber of reciprocating air compressor was designed for constant revolution running condition. For the review, Vibration test was conducted for the performance appraisal of installed dynamic vibration absorber in the reciprocating air compressor. As a result of the test, the performance of dynamic vibration absorber was satisfactory.

• Journal of the Semiconductor & Display Technology
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• v.21 no.4
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• pp.59-64
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• 2022

Vibration is one of the factors that degrades the performance of equipment and measurement equipment used in high-tech industries such as semiconductors and display. The vibration isolator is classified into passive type and active type. The passive vibration isolator has the weakness of insufficient vibration isolation performance in the low frequency band, so an active vibration control system that can overcome these problems is used recently. In this paper, PID controller is used to control the active vibration isolator. Methods for setting the gain of the PID controller include the Zeigler-Nichols method, the pole placement method. These methods have the disadvantage of requiring a lot of time or knowing the system model accurately. This paper proposes the gain auto tuning method of the active vibration isolator applied with the PSO algorithm, which is an optimization algorithm that is easy to implement and has stable convergence performance with low calculations. It is expected that it will be possible to improve vibration isolation performance and reduce the time required for gain tuning by applying the proposed PSO algorithm to the active vibration isolator.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.4
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• pp.352-356
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• 2011

The isolation performance of a linear vibration isolator is limited to the ratio of stiffness to mass it supports. The stiffness of the isolator must be large enough to hold the weight. This results in the deterioration of the isolation performance. Recently, to overcome this fundamental limitation, the HSLDS(high-static-low-dynamic-stiffness) magnetic vibration isolator was introduced and its isolation characteristic was investigated theoretically. In this paper, the isolation performance of the HSLDS magnetic isolator is examined experimentally. Considerable amount of experiments are performed by carefully considering nonlinear characteristics. The experimental results verify the practical usability promisingly and agree with the theoretical studies, i.e. its performance is largely dependent on the key design parameter.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.113-118
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• 2009

A designer regards the vibration system as a linear system. However, in real world, nonlinearity of a vibration system should exist caused by various factors like manufacturing conditions or uncertain material properties. So, properties of a spring and a damper which are consisting the vibration system have statistical distribution. Therefore, a designer needs to analyze the statistical nonlinearity in a vibration system. In this paper, $1^{st}$ Taylor series expansion method and univariate dimension reduction method apply to a performance measure of nonlinear vibration system, and compare each result. And then, merits and demerits of each method are discussed. For apply more actual problem, a performance measure population is estimated based on design variable samples like properties of spring or damper.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.5
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• pp.108-122
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• 2001

As bridge design is advancing toward the performance-based design. it becomes increasingly important to monitor and re-evaluate the long-term structural performance of bridges. Such information is essential in developing performance criteria for design. In this research. sensor systems for long-term structural performance monitoring have been installed on two highway bridges. Pre1iminary vibration measurement and data analysis have been performed on these instrumented bridges. On one bridge, ambient vibration data have been collected. based on which natural frequencies and mode shapes have been extracted using various methods and compared with those obtained by the preliminary finite element analysis. On the other bridge, braking and bumping vibration tests have been carried out using a water truck In addition to ambient vibration tests. Natural frequencies and mode shapes have been derived and the results by the breaking and bumping vibration tests have been compared. For the development of a three dimensional baseline finite element model, the new methodology using a neural network is proposed. The proposed one have been verified and applied to develop the baseline model of the bridge.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.2 s.119
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• pp.114-120
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• 2007

Vibration performance of a 6 kW stand-alone wind turbine(W/T) generator is investigated under the wind environment of Daegwanryung mountain area. In the W/T, wind condition, power performance and structural stability are correlated each other An integrated monitoring system which consists of accelerometers, anemometers, power meters and auxiliary sensors for atmospheric data are constructed to measure the required data simultaneously. Based upon the data acquired over a long period of time, vibration performance of the W/T structure is estimated with annual wind data and generating power performance. Within the operating speed range, possibility of severe nitration is diagnosed. Vibration sources are identified and countermeasures are proposed. The goal of the study is to offer the basic information on W/T vibration performance at the design stage of a small stand alone W/T structure.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.1
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• pp.24-32
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• 2015

Pulse tube-type spaceborne cryocooler is widely used to cool down the infrared sensor of observation satellites. However, such cryocooler also generates micro-vibration which is the one of main sources to seriously affect the image quality during its on-orbit operation. Therefore, to comply with the mission requirement of high resolution observation satellite, additional technical efforts have been required. In this study, we proposed a spaceborne cryocooler passive vibration isolator using SMA mesh washer, which guarantees the structural safety of both the micro-vibration disturbance source and itself under harsh launch vibration loads without an additional holding mechanism and the micro-vibration isolation performance on orbit environment. To verify the micro-vibration isolation performance of the proposed vibration isolator, we performed the micro-vibration isolation measurement test using the dedicated micro-vibration measurement device proposed in this study.

• Structural Engineering and Mechanics
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• v.55 no.2
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• pp.413-434
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• 2015

The vibrations caused by metro operation propagate through surrounding soil, further induce secondary vibrations of the nearby underground structures and adjacent buildings. In order to investigate the effects of vibrations caused by metro on use performance of buildings, vibration experiment of Chengdu museum was carried out firstly. Then, the coupling tunnel-soil-structure finite element model was established with software ANSYS detailedly, providing a useful tool for investigating the vibration performances of structures. Furthermore, the dynamic responses and vibration predictions of museum building were obtained respectively by the whole process time-domain analysis and frequency-domain analysis, which were compared with the vibration reference values of museum. Quantitative analyses of the museum building performance were carried out, and the possible tendency and changing laws of vibration level with floors were proposed. Finally, the related vibration isolation measures were compared and discussed. The tests and analysis results show that: The vertical vibration responses almost increased with the increasing of building floors, while weak floors existed for the curve of horizontal vibration; The vertical vibrations were larger than the horizontal vibrations, indicating the vibration performances of building caused by metro were characterized with vertical vibrations; The frequencies of the museum corresponding to the peak vibration levels were around 6~17Hz; The damping effect of structure with 33m-span cantilever on vertical vibration was obvious, however, the damping effect of structure with foundation vibration isolators was not obvious.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.442-453
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• 2016

A significant source of vibration in helicopters is the main rotor system, and it is a technical challenge to reduce the vibration in order to ensure the comfort of crew and passengers. Several types of passive devices have been applied to conventional helicopters in order to reduce the vibration. In recent years, helicopter manufacturers have increasingly adopted active vibration control systems (AVCSs) due to their superior performance with lower weight compared with passive devices. AVCSs can also maintain their performance over aircraft configuration and flight condition changes. As part of the development of AVCS software for light civil helicopter (LCH) applications, a test bench is constructed and vibration control tests and simulations are performed in this study. The test bench, which represents the airframe, is excited using a pair of counter rotating force generators (CRFGs) and a multiple input single output (MISO) AVCS that consists of three accelerometer sensors and a pair of CRFGs; a filtered-x least mean square (LMS) algorithm is applied for the vibration reduction. First, the vibration control tests are performed with uniform sensor weights; then, the change in the control performance according to changes in the sensor weight is investigated and compared with the simulation results. It is found that the vibration control performance can be tuned through adjusting the weights of the three sensors, even if only one actuator is used.