• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2004.10a
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• pp.96-101
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• 2004

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2005.10a
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• pp.114-120
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• 2005

• Journal of KSNVE
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• v.10 no.3
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• pp.401-409
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• 2000

Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins through the motor air-gap. When a relative misalignment of rotor in the air-gap center exists on the assemblage it is considered to influence the motor system characteristics, depending on the degree of misalignment. The rotor-motor system used in a washing machine is modeled using FE-TM and a magnetic force of BLDC motor with radial rotor eccentricity is analyzed. And the transient whirl responses of a rotor system with relative misalignment in the motor air-gap are investigated considering mechanical origins and magnetic effects. Results show that rotor misalignment in the air-gap affect the vibration of the rotor-motor system.

• Journal of KSNVE
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• v.7 no.6
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• pp.1015-1023
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• 1997

Rotordynamic analysis of a multistage turbine pump using finite element method is performed to investigate the effects of seal wear on its system behavior. Stiffness and damping coefficents of the 2-axial grooved bearing are obtained as functions of rotating speed. Stiffness and damping coefficients of plane annuler seals are calculated as functions of rotating speed as well as seal clearance of seals become larger, these stiffness and damping coefficients decrease drastically so that there can be significant changes in whirl natural frequencies and damping characteristics of the pump rotor system. Although a pump is designed to operate with a sufficient seperation margin from the 1st critical speed, seal wear due to long operation may cause a sudden increase in vibration amplitude by resonance shift and reduce seal damping capability.

• Journal of KSNVE
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• v.7 no.3
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• pp.467-475
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• 1997

A rotor-bearing system has been investigated, including internal damping and axial torque using finite dynamic elements. A procedure is presented for dynamic modeling of rotor-bearing system which consist of finite dynamic shaft elements, rigid disk, and bearing and seal. A finite dynamic element model including the effects of rotatory inertia, gyroscopic moments, axial force, and axial torque is developed using the frequency dependent shape function. The natural whirl speeds, stability, and unbalance response of rotor system are calculated on several cases and compared with the conventional finite elements.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.547-550
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• 1997

The dynamic behavior of rotor-bearing system has been investigated using finite element method. A procedure is presented for dynamic modeling of rotor-bearing system which consist of shaft elements, rigid disk, flexible bearing and support structures. A finite element model including the effects of rotary inertia, shear deformation, gyroscopic moments is developed. Linear stiffness and damping coefficient are calculated for 3 lobe sleeve bearing. The whirl frequency, mode shape, stability and unbalance response of rotor system included effect of bearing coefficient and support structures are calculated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1450-1454
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• 2000

In order to understand dynamic characteristics of centrifugal compressor supported foil bearing, of which normal operating speed is about 20,000 ${\sim}$ 50,000 rpm, the rotor whirl is measured using gap sensors. Not only critical speeds of rotor system but also stability of rotor whirl, which are main concerns of the turbo compressor system, are measured using gap sensors by varying the rotating speed the rotor. The stiffness characteristics of bearing system is shown to be almost invariant according to speed variation by the measurement of eccentricity. In addition, from the directional power spectral density function of the measured vibration signal, the isotropy stiffness characteristics of foil bearing system is discussed.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.10
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• pp.37-44
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• 2002

The dynamic behavior of rotor-bearing system has been investigated using finite element method. A procedure is presented for dynamic modeling of rotor-bearing system which consists of shaft elements, rigid disk, flexible bearing and support structure. A finite element model including the effects of rotary inertia, shear deformation, gyroscopic moments is developed. Linear stiffness and damping coefficients are calculated for 2 lobe sleeve bearing. The whirl frequency, mode shape, stability and unbalance response of rotor system including effects of bearing coefficient and support structures are calculated.

• Tribology and Lubricants
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• v.17 no.1
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• pp.56-63
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• 2001

The dynamic behavior of rotor-bearing system used in swash plate compressor has been investigated using the combined methodologies of finite elements and transfer matrices. The finite element is formulated including the field element for a shaft section and the point element for swash plate, disk pulley and bearings. The Houbolt method is used to consider the time march for the integration of the system equations. The transient whirl response of rotating shaft supported on roller bearings is obtained, considering compression forces and unbalance forces at swash plate and driving pulley. And, the steady state displacements of the rotor are compared with a variation in unbalance mass. Results show that the loci of rotating shaft considering unbalance forces and external compression forces are more severe in flutter motion than with only unbalance forces.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.11
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• pp.1864-1872
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• 2003

Hidden Markov Model(HMM) has been widely used in speech recognition, however, its use in machine condition monitoring has been very limited despite its good potential. In this paper, HMM is used to recognize rotor fault pattern. First, we set up rotor kit under unbalance and oil whirl conditions. Time signals of two failure conditions were sampled and translated to auto power spectrums. Using filter bank, feature vectors were calculated from these auto power spectrums. Next, continuous HMM and discrete HMM were trained with scaled forward/backward variables and diagonal covariance matrix. Finally, each HMM was applied to all sampled data to prove fault recognition ability. It was found that HMM has good recognition ability despite of small number of training data set in rotor fault pattern recognition.