• Tribology and Lubricants
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• v.28 no.6
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• pp.328-332
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• 2012

Generated Axial Force (GAF) due to internal friction at Constant Velocity (CV) joints is one of the causes generating vibration problems such as shudder in vehicle. In this study, the GAF measuring tester is developed to precisely measure GAF caused by internal friction in CV joints. As the developed tester can control temperature at joint, driving torque, angle of rotation and joint angles, actual driving conditions such as sudden acceleration can be applied to the machine. GAFs are measured and compared by using different types of grease in tripod housing. Also GAFs are measured for both new and used CV joints to be compared and analyzed. The test result shows the repeatability and consistency of the tester in terms of the different test conditions. By using the developed CV joint tester, friction performance of the joint can be evaluated by proposing the best CV joints as well as greases generating the lowest GAF.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.1000-1005
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• 2003

The shock separation test simulates the environmental effects of the spacecraft separation from launch vehicle. The shock separation test for a structural model of KOMPSAT-Ⅱ(Korea Multi-Purpose SATellite Ⅱ) was performed in SITC(Satellite Integration ＆ Test Center) launch environmental test hall at KARI(Korea Aerospace Research Institute) to verify the shock test requirement of the spacecraft, to predict the induced acceleration responses on the primary structures and payloads by the explosion of pyre-lock and to perform mechanical fit check. The spacecraft with S/A was mated vertically to LV(Launch Vehicle) adapter simulator via a clamp band, then hoisted and suspended above a foam test bed by four isolation springs secured to the spacecraft hoist fittings to isolate the payload platform shock wave from the sling elements. For separation process, real pyre-devices were used and the time response signals from 60 accelerometers installed on the interested points was acquired and recorded. The SRS responses for each response channels were calculated and the achieved SRS's on the separation plane was reviewed and evaluated in comparison to the ICD(Interface Control Document) value.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.3
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• pp.251-260
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• 2009

In this paper, we studied on an attenuation effect of automobile exhaust noise according to the direction of canceling speaker in ANC system. Automobile exhaust noise was recorded at 800 rpm, 3500 rpm and 5000 rpm of a diesel engine. Directions of canceling speaker can be set to $30^{\circ}$, $90^{\circ}$ and $150^{\circ}$ against the primary noise flow by acrylic ducts to be made for the experimentation. DSP board with TMS320C6416 chip of Texas Instrument Co. used to control the ANC system. The algorithm of this ANC system applied the Filtered-x-LMS algorithm that is modified to compensate for a property of DSP input signal and the secondary-path effect. As an experiment result, the direction of canceling speaker was proved to influence the reduction effect of noise. The $150^{\circ}$ duct in the attenuation effect of noise showed a better result than the $90^{\circ}$ or $30^{\circ}$ duct.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.3
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• pp.298-307
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• 2016

In the building process of FPSOs(floating production, storage and offloading units) is the increasing demand of high performance piping joints that can be installed on its turret system and maintain smooth and long-term flow of ultra-high pressure crude oil, being subjected to external excitations such as wind and wave on the sea. Following such a trend, in this paper, a new-type piping joint of four effective degrees of freedom has been designed, and its dynamic characteristics predicted through mathematical modeling and computer simulations. Moreover, via an example it was shown how the yaw motion in particular can be independently controlled for future durability test despite strong kinetic couplings.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.2
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• pp.263-271
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• 2008

Compressor radiated noise is one of the dominant noise for the outdoor unit of the air conditioner. Therefore, air conditioner makers are trying to reduce it continuously. Even though noise absorption and isolation technology are one of the important parts for reducing the noise from the compressor, it is usually treated to the substitute technology when the noise from the compressor is very difficult to reduce by the compressor noise control only. In this paper, we focus on the property of the sound insulation for the cabinet and measure it applying the theory of the sound transmission loss and insertion loss of the simple enclosure. The insertion loss is evaluated by the experiments according to the thickness and the aperture of the partition in the cabinet.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.178-185
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• 2011

The micro-perforated panel absorber (MPPA) is one of promising noise control elements because of its applicability to extreme environments where general porous materials cannot be used. Since the MPPA is inherently non-porous sound absorber, it can be a good candidate of acoustic protection system of a space launcher. The overall sound pressure level inside payload fairings of commercial launch vehicles is so high (around 140 dB OASPL) that the conventional linear impedance model cannot be directly applied to the design of the acoustic protection systems. In this paper an acoustic impedance models of a micro-perforated panel absorber at high sound pressure environment were reviewed and the use of the impedance on the practical design of MPPAs was addressed. The variation of absorption characteristics of MPPA was discussed according to the design parameters, e.g., perforation ratio, the minute hole diameter, the thickness of MPP and the incident sound pressure level.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.8
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• pp.681-689
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• 2013

The commercial tools to simulate the non-linear dynamic characteristics of wind turbine system are various but, the tool take much time to simulate the control algorithm and require many input variables. In this paper, the procedures to derive the simplified 4-degree-of-freedom mathematical model of a 2-MW wind turbine which could be used at the initial design stage of the controller are proposed based on RISO's suggested method. In this model, the 1st tower fore-after bending motion and 1st blade flapping motion are also considered in addition to the rotor-generator rotation motion in the 2-DOF model. The effectiveness of the 4-DOF model is examined comparing with the 2-DOF model and verification of the simplified model is accomplished through modal analysis for whole wind turbine system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.1
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• pp.41-48
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• 2013

In this work, 4-DOF ER haptic master is proposed and integrated with a slave robot for minimally invasive surgery(MIS). Using a controllable ER fluid, the haptic master can generate a repulsive force/torque with the 4-DOF motion. For realization of master-slave robot system, the motion command of the haptic master is realized by slave surgery robot. In order to follow the 4-DOF motion of the haptic master, novel mechanism of slave surgery robot with gimbal joint is devised. Accordingly, the haptic master-slave robot system is established by incorporating the slave robot with the haptic master device in which the desired repulsive force/torque and position are transferred to each other via wireless communications. In order to obtain the desired force/torque and position trajectories, tracking controllers for haptic master and slave robot are designed and implemented, respectively. It has been demonstrated that the desired effective torque tracking control performance is well achieved using the proposed haptic master-slave robot system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.1
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• pp.25-33
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• 2013

The floating offshore wind turbines are usually exposed to the wave and wind excitations which are irregular and undirected. In this paper, the sloshing characteristics of annular cylindrical tank were experimentally investigated to reduce the structural dynamic motion of floating offshore wind turbine which is robust to the irregular change of excitation direction of wind and wave. The formula for the natural sloshing frequencies of this annular cylindrical tank was derived theoretically. In order to validate this formula, the shaking equipment was established and frequency response functions were measured. Two types of tank were considered. The first and second natural sloshing frequencies were investigated according to the depth of the water. It has been observed that between theoretical and experimental results shows a good agreement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.373-377
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• 2002

In this study, we suggested a slim-type actuator that can be controlled in radial direction for compensating coma aberration in high-capacity optical storage devices. To deal successfully with narrow space in slim-type optical pick-up for notebook pc device, additional yokes for tilting motion are integrated into main yoke of the actuator. And the location of tilting coils is determined for mass-b3lancing effect to achieve optimal configuration for high driving sensitivity. We also suggested new concept of lens holder to guarantee excellent stability of control system by enhancing the gain margin at secondary resonant frequency. The concept was realized by forming damping sections in the lens holder, which prevent vibrational energy from transferring to lens. An exclusive measurement system was newly developed for fast and precise measurement of dynamic characteristics of actuators and utilized for the practical use. We hope to make good use of this system also in time to come.