• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.10a
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• pp.157-161
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• 1993

Optical devices and electronic equipments used in the laboratory of the synchrotron light source building of the accelerator have stringent vibration limits. In order to control the vibration of the building structure and HVAC systems which are main vibration sources are evaluated using experimental modal analysis. Double anti-vibration system is used for the HVAC system and results show that the double anti-vibration system reduces the vibrations of the building to acceptable levels.

• Journal of Power System Engineering
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• v.13 no.1
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• pp.33-38
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• 2009

In this study, the nose of cam in the automobile engine was modelled into circular disk to analyze the torsional vibration of the cam shaft. The distance between disks was fixed, but the diameter of disks was changed. The torsional vibration of the cam shaft was studied experimentally by the motion of the modelled disk with changing the disk diameter. And the sizes of the modelled disk were selected not to show the natural frequencies over all the experimental ranges. The torsional vibration meter used in this study has a laser system with non-contact measurement method, which can measure both torsional angular vibration velocity and torsional angular vibration displacement simultaneously. The Experimental analysis shows that the characteristics of the torsional vibration in the horizontal rotating shaft can be considerably affected by the arrangement of the modelled disks.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.640-646
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• 2001

The torsional vibration monitoring system(TVM) for large diesel engines was developed and applied by manufacturers of torsional vibration damper, flexible coupling and diesel engine since 1990s. And demands of TVM have been steadily increased to operate safely engine and to extend maintenance interval of damper and flexible coupling. In this paper, the experimental methods and algorithms of TVM development which used the existing PC, turning wheel and speed sensors in ship are introduced.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1998.10a
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• pp.274-285
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• 1998

Increasing flexibility and lightness of recently built high-rise buildings make the structures susceptible to loads such as earthquakes and winds. Therefore, higher performance vibration control systems to reduce the vibration levels are demanded more than any time in the past. One of typical active vibration control systems is the active mass damper(AMD). In this paper, an active vibration control system consisting of small shaking table, building model, sensors, signal processing board and AMD is constructed. The dynamic characteristics of these individual systems are investigated through the experimental study. The performance of the active vibration control system is verified through harmonic resonant load excitation on building model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.505-509
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• 2001

When the spindle is rotated for machining the workpiece, the vibration is generated due to the spindle unbalance. This vibration affects surface finish, dimensional accuracy, tool life, and spindle bearings. To compensate this effect of the spindle unbalance, the spindle system using an EME(electro magnetic exciter)is proposed in this paper. In the proposed spindle system, the vibration due to the spindle unbalance is monitored using vibration sensors and is compensated by electromagnetic attractive forces generated in the EME which are excited by anti-direction forces corresponded with the measured unbalance. Firstly, the spindle system using an EME and control system are constructed to compensate the effect of spindle unbalance in this paper. And then the system is modeled by bond graph to analyze the system. Finally, a controller for vibration compensation due to spindle unbalance is designed and is implemented in real experimental system. As a result, experimental results show this proposed spindle system is very effective to compensate the spindle unbalance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.120-124
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• 2003

NVH issue at idle condition is one of the major concerns of Passenger and Commercial Vehicle including Sports Utility Vehicle Especially steering wheel vibration at idle condition is a very complex problem and affected by firing frequency of the engine, stiffness of a steering wheel system and the body to which the steering wheel system is attached. To avoid vibration mode coupling between each system of a vehicle, experimental and analytical method has been used at the pre-prototype stage. The resonance frequency of the body and the frame has been decoupled by CAE and the resonance frequency of steering wheel system has been set in between the 1st bending frequency of body and frame. These Results has been used as design guidelines tot the prototype drawing stage. The experimental verification of tile modified pre-prototype vehicle shows good results of the vibration mode decouple. Modal test of prototype vehicle also confirms the vibration mode decouple between each system.

• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.129-137
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• 2000

In the prototype stage of a car developing program, the efficiency of trouble shooting is an important factor to be considered. Structural modifications by the design sensitivity analysis are applied to a steering wheel system for improving the idle vibration of the prototype passenger car. For the design sensitivity analysis, the experimental modal analysis for the steering system attached to a body-in-white is fulfilled and the modal parameters extracted from the experimental data are used to predict the effect of structural modification, The design sensitivity results rank the locations to be reinforced in terms of frequency variation. The modification of steering system according to the sensitivity analysis results shifted the resonant frequency of the system effectively. In addition, the idle test of the car after the structural modifications f steering system shows that the proposed method can reduce vibration of the steering wheel efficiently.

• Smart Structures and Systems
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• v.15 no.3
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• pp.863-879
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• 2015

This paper experimentally investigates the effectiveness and applicability of the time delay control (TDC) algorithm, which is simple and robust to unknown system dynamics and disturbance, for an active mass damper (AMD) system to mitigate the excessive vibration of a building structure. To this end, the theoretical background including the mathematical formulation of the control system is first described; and then, a thorough experimental study using a shaking table system with a small-scale three-story building structural model is conducted. In the experimental tests, the performance of the proposed control system is examined by comparing its structural responses with those of the uncontrolled system in the free vibration and forced vibration cases. It is clearly verified from the test results that the TDC algorithm embedded AMD system can effectively reduce the structural response of the building structure.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.9
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• pp.122-132
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• 2000

A simplified modeling approach of forced vibration for occupied car seats was demonstrated by using a mathematical model presented in 'Free Vibration of Car seat and Mannequin System' nonlinear and linear equations of motions were rederived for forced vibration and the transfer function was used to calculate the frequency response function. The experimental apparatus were set up and hydraulic shaker was used to obtain the system responses. Through the tests mannequin's head had a lot of problems and the responses with a head and without a head were measured. To explore the effects of linear dampings and friction moments at the joints linear analyses were performed. New sets of linear spring and damping coefficients and torsional dampings at the joints were calculated through parameter study to match up with experimental results. Good agreement between experimental and simulation frequency response estimates were obtained both in terms of locations of resonances and system deflection shapes at resonance indicating that this is a feasible method of modeling seated occupants.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.149-153
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• 2005

Marine Propulsion shafting system coupled with medium diesel engine forms multi-degree torsional vibration system which consist of many inertia masses such as crank, flywheel, propeller and sometimes gear system is adopted additionally for the purpose of improving propeller's propulsion efficiency or connecting with PTO/PTI. The periodic excitation torques generated by combustion pressure in cylinder and reciprocating masses induce various kinds of vibrations in this shafting system. If the frequency of this excitation torques is equal to the natural frequency of the shafting, the amplitude of the torsional vibration increases steeply and the damage of crankshaft or gears may be occurred by that. This frequency is called critical speed. When making a plan for shafting system, it is important for this frequency to be expected exactly and not to be in commonly used speed. For this reason, this paper introduces the experimental equipment for torsional vibration of marine propulsion shafting system and describes the theoretic and the experimental methods to look for natural frequencies.