• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.987-993
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• 2013

Korean Utility Helicopter(KUH) is the first korean-developed helicopter. Its first flight was performed in March 2010 and then its development was completed successfully by June 2012. During flight test phase, KUH faced various vibration problems and appropriate vibration-reduction devices were designed and applied to solve the problems. The vibration-reduction devices were applied to main rotor blades, main gear box(MGB) supporting structure, cockpit, cabin and pilot seats to reduce rotor-induced 4/rev vibration. Also, dome-fairing was introduced in order to reduce the tail-shake vibration. This paper shows design technique and flight test results for vibration-reduction devices that have been incorporated into KUH.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.96-102
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• 1997

Eigenvalue analysis of vibration mode and an analysis by frequency response among the methods of predicting gear noise are related with transmitting sound of vibration. In this study we intended to reduce the vibration noise of differential gear by reducing torque fluctuation of drive pinion shaft which causes vibration noise of differential gear in rear wheel drive vehicles. For this we developed multi-degree of freedom analysis model in which mass moment of inertia and torsional spring combined and we examined the influence of torsional vibration of driveline elements by performing forced vibration analysis of engine excitation torque. We studied the methods for reducing torsional vibration of driveline according to the design factor of propeller shaft and examined the effects reducing vibration in differential gear by applying flexible coupling.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.420-424
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• 1994

In this paper, an active suspension system considering the wheel hop is studied for a quarter car model. A LQ controller controls an active suspension system in which a vibration absorber is attached to the wheel axis. The vibration absorber is adopted to reduce the vibration near the natural frequency of the unsprung mass, and the LQ controller is used to control the vibration near the natural frequency of the sprung mass. The perfomance of the control system considering the wheel hop is compared with that of a LQ control system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.589-593
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• 1995

The vibration of rotors in high speed sometimes leads to system failure or reduces the system life, and has a direct connection with stability. In this paper, the system's modelling was conducted in experimentally and the controller was designed to reduce the vibration due to the rotor unbalance using Squeeze Film Damper(SFD). SFD vibration control was achieved in constant rotating speed based on the controller designed. the control was confirmed working quite well in terms of both numerical simulation and experiment.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.80-84
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• 1996

A Switched Reluctance Motor(SRM) has a torque pulsating inherently due to characteristics of pulse driving. A torque pulsating causes noise and sound vibration. To reduce a noise, a torque pulsating shall be controlled. Many efforts to make flat-topped current has been proposed to minimize a torque pulsating up to now. This paper proposed a control scheme to minimize the vibration of SRM by controlling the vibration directly by using of self-turning technique. The experimental results show that the proposed control scheme is effective in reducing the torque ripple and noise.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.139-145
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• 1997

Nowadays, the axial stiffness of crankshaft of long-stroke diesel engine is low compared to that of the old types of engine by increasing stroke/bore ratio and major critical speed might occur within engine operation speed. An axial damper needs to be installed in order to reduce the axial vibration of the crankshaft in the event of reduced or stopped axial damper function are discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.779-781
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• 2005

In this paper, Firstly, it is shown that the bending mode vibration source of vertical pump system is comparatively large because resonance. Secondly in order to reduce the bending mode vibration of vertical pump, The improvement of some boundary condition have been developed and its effectiveness is investigated as appling it at the vertical pump system pratically.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.516-521
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• 2004

TEEE(Thermoplastic ether-ester elastomer) is expected to reduce the noise and vibration from railway because its unique properties such as porosity. in this study, after building TEEE rail pad at established rail, we conducted practical test and vibration test to inquire the field application and endurance of TEEE material. The test results showed that TEEE material was lower vibration than EVA material, therefore, TEEE material was effective from a vibration reduction point of view.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.282-286
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• 2000

In this paper, magneto-rheological(MR) damper is studied for vibration control of large infra structures under earthquake. Generally, active control devices need a large control force and a high power supply system to reduce the vibration effectively. Large and miss tuned control force may induce the dangerous situation such that the generated large control force acts to amplify the structural vibration. Recently, to overcome the weaknesses of the active control, the semi-active control method is suggested by many researchers. Semi-active control uses the passive control device of which the characteristics can be modified. Control force of the semi-active device is not generated from the actuator with power supply. It is generated as a dynamic reaction force of the device same as in the passive control case, so the control system is inherently stable and robust. Unlike the case of passive control, control force of semi-active control is adjusted depending on the measured response of the structure, so the vibration can be reduced more effectively against various unknown environmental loads. Magneto-rheological(MR) damper is one of the semi-active devices. Dynamic characteristics of the MR material can be changed by applying the magnetic fields. So the control of MR damper needs only small power. Response time of MR to the input voltage is very short, so the high performance control is possible. MR damper has a high force capacity so it is adequate to the vibration control of large infra structure. Because MR damper has a nonlinear property, normal control method used in active control may not be effective. Clipped optimal control, modified bang-bang control etc. have been suggested to MR damper by many researchers. In this study, sliding mode fuzzy control(SMFC) is applied to MR damper. Genetic algorithm is used for the controller tuning. To verify the applicability of MR damper and suggested algorithm, numerical simulation on the aseismic control is carried out. Simulation model is three-story building structure, which was used in the paper of Dyke, et al. The control performance is compared with clipped optimal control. The present results indicate that the SMFC algorithm can reduce the earthquake-induced vibration very effectively.

• Journal of KSNVE
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• v.20 no.6
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• pp.24-28
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• 2010

Many methodologies have been explored to reduce helicopter vibration. Trailing edge flaps for such a purpose have been studied for the past twenty years. A brief overview of the introduction of active vibration controls using trailing edge flaps and smart actuators is presented in series. This is the fourth article, in which a piezoelectric resonant actuation system with a buckling-beam motion amplifier for active trailing edge flaps is presented.