• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.5
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• pp.313-320
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• 2015

A 2-axis gimbal-type X-band antenna has been widely used to effectively transmit the high resolution image data from the observation satellite to the desired ground station. However, a discontinuous stepper motor activation for rotating the pointing mechanism in azimuth and elevation directions induces undesirable micro-vibration disturbances which can result in the image quality degradation of a high-resolution observation satellite. To enhance the image quality of the observation satellite, attenuating the micro-vibration induced by an activation of the stepper motor for rotational movements of the antenna is important task. In this study, we proposed a low-rotational-stiffness blade gear applied to the output shaft of the stepper motor to obtain the micro-vibration isolation performance. The design of the blade gear was performed through the structure analysis such that this gear is satisfied with the margin of safety rule under the derived torque budget. In addition, the micro-vibration isolation performance of the blade gear was verified through the micro-vibration measurement test using the dedicated micro-vibration measurement device proposed in this study.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.669-674
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• 2013

To design the optimized low noise planetary gear sets, a program called pRMC(planetary run many cases) is developed. The pRMC is especially using a combination analysis method for all gear specifications and also able to analyze any type of planetary gear sets. The pRMC is composed of the 5 sections those are generate, setting, evaluate, combine and analysis. After calculating all candidate gear sets, the pRMC could show many results that represent the character of each gear set including the transmission error which is the main gear noise factor, the contact ratios, the bending stress and so on. By comparing the results objectively, user could predict and select the optimized gear set which has quiet noise level and desired durability. The planetary gear designed by pRMC could have reduced noise and vibration level from 5 to 10 dB than previous-designed one.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.762-767
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• 1998

The main torsional vibration source of the powertrain is the fluctuation of engine torque. The gear rattle is impact generating in the backlash of the free gear due to this torsional vibration. Optimization of the clutch torsional characteristic is one of the effective method to reduce the idle gear rattle. Many researches have been reported on this problem but only few of them give sufficient consideration to the detailed clutch modeling and the experiment. This paper pays attention to the optimization of clutch design parameters and the experiment to reduce the idle gear rattle vibration and noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.697-701
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• 2007

In this paper, noise sources of a planocentric gear reducer are identified by experimental mehod. This study consider a reduction method of a noise/vibration about the gear, axle, bearing and others. Namely, the purpose of this study is to reduce a noise/vibration for a stability of the total system. Form the data to be measured through an experimental method, the problems of the gear, axle, bearing and others are examined closely, and the reducer is derived the model to be the engineering. The mechanism of the problem occurrence is examined through a parametric research about an each influence factor(Load). Lastly, the results of this study propose the model to be improved.

• Journal of Power System Engineering
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• v.11 no.4
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• pp.65-71
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• 2007

According to the survey, abnormal condition of the system is the main source for interrupting an elevator service, especially faults in worm gears used for the traction machine. Worm gear is popularly used in traction machine for middle and low speed elevators. Elevators need high reliability and stability, because they are closely related to human life. Usually, traction machine is applied to drive the elevators that have height about 35 m and it is an important mechanical unit for riding quality in elevators. There are some research results about types of vibration fault for worm gear in International Association Elevator Engineers (IAEE). But this study concerns with diagnosis of various faults in elevator worm gear using vibration signal. The analysis of fault characteristics is compared with previous researches in traction machine.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.316-323
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• 2003

The gear system is commonly applied in the marine propulsion shafting system using the diesel engine with the power take off/in system and it also is necessary to reduce propeller revolution increasing the propulsion efficiency. The diesel engine has the advantage more than other thermal engines in high thermal efficiency and mobility. But the large vibratory torque which induced by higher combustion pressure is transmitted to these gears. In this paper, the surface durability and bending stress of gear system considering vibratory and transient torque is evaluated by ISO and AGMA regulation. And the influence of these in gear design is investigated with the theoretical analysis and onboard measurement result of torsional vibration.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.39-56
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• 2009

Vibration is an undesirable phenomenon in a dynamic system like lightly damped aerospace structures and active vibration control has gradually been employed to suppress vibration. The objective of the current investigation is to introduce an active torsional magneto-rheological (MR) fluid based damper for vibration control of a typical nose landing gear. They offer the adaptability of active control devices without requiring the associated large power sources. A torsional damper is designed and developed based on Bingham plastic shear flow model. The numerical analysis is carried out to estimate the damping coefficient and damping force. The designed damper is fabricated and an experimental setup is also established to characterize the damper and these results are compared with the analytical results. A typical FE model of Nose landing gear is developed to study the effectiveness of the damper. Open loop response analysis has been carried out and response levels are monitored at the piston tip of a nose landing gear for various loading conditions without damper and with MR-damper as semi-active device. The closed-loop full state feedback control scheme by the pole-placement technique is also applied to control the landing gear instability of an aircraft.

• Structural Engineering and Mechanics
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• v.88 no.4
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• pp.389-403
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• 2023

In order to explore the influence of tooth root cracks on the dynamic characteristics of multi-stage planetary gear transmission systems, a concentrated parameter method was used to construct a nonlinear dynamic model of the system with 30-DOF in bending and torsion, taking into account factors such as crack depth, length, angle, error, time-varying meshing stiffness (TVMS), and damping. In the model, the energy method was used to establish a TVMS model with cracks, and the influence of cracks on the TVMS of the system was studied. By using the Runge- Kutta method to calculate the differential equations of system dynamics, a series of system vibration diagrams containing cracks were obtained, and the influence of different crack parameters on the vibration of the system was analyzed. And vibration testing experiments were conducted on the system with planetary gear cracks. The results show that when the gear contains cracks, the TVMS of the system will decrease, and as the cracks intensify, the TVMS will decrease. When cracks appear on the II-stage planetary gear, the system will experience impact effects with intervals of rotation cycles of the II-stage planetary gear. There will be obvious sidebands near the meshing frequency doubling, and the vibration trajectory of the gear will also become disordered. These situations will become more and more obvious as the degree of cracks intensifies. Through experiments, the theoretical results are in good agreement with experimental results, verifying the correctness of the theoretical model. This provides a theoretical basis for fault diagnosis and reliability research of the system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.8
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• pp.643-650
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• 2014

Gear transmission system is widely applied in engineering. As the problem of contact fatigue, wear, lubrication failure etc, the condition of gear teeth contacts will be worse. The vibration and sound signals in the gear system will be affected by the some failures like scuffing, abrasive wear and spalling due to the deterioration of gear teeth surface. By studying the estimation of specific film thickness, measurement of reduction in tooth thickness, visual examination of wear mechanisms on the gear teeth and their effects on the statistical parameters of vibration and sound signals, the research obtained the satisfactory results on accessing the surface fatigue wear in a spur gear system. The paper utilizes the relationship between statistical parameters obtained from sound signals and Stribeck curve to confirm the hypothesis of dependency of surface fatigue wear, specific film thickness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.4
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• pp.537-543
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• 2003

Transient vibration generated by developing localized fault in gear can be used as indicators in gear fault detection. This vibration signal suffers from the background noise such as gear meshing frequency and its harmonics and broadband noise. Thus in order to extract the information about the only gear fault from the raw vibration signal measured on the gearbox this signal is processed to reduce the background noise with many kinds of signal-processing tools. However, these signal-processing tools are often very complex and time waste. Thus. in this paper. we propose a novel approach detecting the damage of gearbox and analyzing its pattern using the raw vibration signal. In order to do this, the residual signal. which consists of the sideband components of the gear meshing frequent) and its harmonics frequencies, is extracted from the raw signal by the power spectral density (PSD) to obtain the information about the fault and is used as the input data of the artificial neural network (ANN) for analysis of the pattern of gear fault. This novel approach has been very successfully applied to the damage analysis of a laboratory gearbox.