• Journal of KSNVE
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• v.9 no.3
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• pp.525-534
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• 1999

The present paper proposes a generalized modal analysis procedure for non-uniform, distributed-parameter rotor-bearing systems. An exact element matrix is derived for a Timoshenko shaft model which contains rotary inertia, shear deformation, gyroscopic effect and internal damping. Complex coordinates system is adopted for the convenience in formulation. A generalized orthogonality condition is provided to make the modal decomposition possible. The generalized modal analysis by using a modal decomposition delivers exact and closed form solutions both for frequency and time responses. Two numerical examples are presented for illustrating the proposed method. The numerical study proves that the proposed method is very efficient and useful for the analysis of distributed-parameter rotor-bearing systems.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.515-517
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• 1997

In the industrial motor drive system, a shaft torsional vibration is often generated when a motor and a load are connected with a flexible shaft. This paper treats the vibration suppression control of such a system. In this paper, two-degree-of-freedom(TDOF) control of the two-mass resonant system using the $H_{\infty}$ filter is proposed. TDOF control method satisfies the command following property and the internal stability at the same. The $H_{\infty}$ filter is robust in noise and disturbance. Simulation results show the validity of the proposed control method.

• Proceedings of the KIEE Conference
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• 2002.11c
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• pp.42-45
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• 2002

In the two-mass motor drive system driving a load through a flexible shaft or transmission system, a shaft torsional vibration is often generated. The overshoot of the motor drive system easily causes vibration. In this case I-PD controller has been generally used in speed control, because of the simplicity of structure. This paper using an analytical pole assignment design, proposes the overshoot formulas, and the settling time formula. The objective of this paper is to provide a design method of I-PD controller by using overshoot formulas, and settling time formula. The simulation results show that we can design the controller with desired overshoot and settling time.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.134-137
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• 2005

Recently, in VLCC, shafting system is stiffer due to large engine power whereas hull structure is more flexible due to scantling optimization, which can be suffered from alignment damage by incompatibility between shafting and hull, In this study, shafting system without stern tube forward bush was adapted for less sensitive system against external factors. Also, shaft alignment analysis was considered with hull deflection at various ship loading conditions and stern tube after bush of long journal bearing was evaluated by static squeezing pressure and dynamic oil film pressure with sloping control. Whirling vibration was also reviewed to avoid resonance with propeller blade order. So, reliable shafting design for VLCC could be achieved through optimized alignment analysis for the system without stern tube forward bush.

• Journal of Power System Engineering
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• v.1 no.1
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• pp.98-105
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• 1997

In general, crankshafts which are used in internal combustion reciprocating engines are subjects to high torsional vibration. Therefore, a damper is often used to minimize the torsional vibration in reciprocating engines. In this paper, in order to investigate damping performance of viscous damper, the real effective viscosity and complex damping coefficient of silicone oil, and the effective inertia moment of inertia ring are calculated considering the relative motion between damper casing and inertia ring. Based on these results multi-cylinder shaft is modeled into equivalent 2-degree of freedom system and optimum condition is estimated by calculating the amplification factor of viscous damper. Also the test damper was manufactured according to the result of theoretical investigation, the performance and durability was ascertained through experimental examination.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.1
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• pp.67-73
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• 1996

Subsynchronous resonance(SSR) causes a torsional shaft torque on the generator. Damages resulting from the uncontrolled SSR have resulted in the breakdown in the shaft and costs for replacement power. This paper is to determine the feasibility of controlling SSR by the fast modulation of series compensation capacitors. The presence of subsynchronous currents in the system was detected by a subsynchronous relay which was modeled by the transient analysis of control systems(TACS) in electromagnetic transients program (EMTP). The capacitor segments were switched by bi-directional thyristor switches. These were modeled into EMTP. The strategy to switch the capacitors were modeled as a closed loop system. The paper proves that effective control of SSR can be obtained only by the detuning of the system and the removal or blocking of subsynchronous energy from the system. (author). refs., figs., tabs.

• Journal of Advanced Marine Engineering and Technology
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• v.13 no.1
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• pp.69-76
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• 1989

This paper presents a method of the optimum design for rotating shaft of centrifugal pump. That is, the object is to optimize the system in stability at the operating speed, unbalance response in the vicinity of the rotor critical speed, leakage flow of the seals. The objective function is composed of these three elements and is minimized by changing seal cleareance, diamoters, and lengths. A typical double suction centrifugal pump is analyzed and its objective function is presented. Then the optimum dimensions of seals are obtained, and vibration characteristics at both initial and optimum conditions are investigated.

• Journal of KSNVE
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• v.5 no.1
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• pp.49-57
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• 1995

An electronic circuit device is developed such that the displacement between an electromagnet and a moving target can be estimated from the coil current measurement, and then applied to an active magnetic bearing system. In order to levitate the shaft without using displacement sensor the stable control gains are obtained from the linearized model which includes the gap estimation circuit. Experimental results show that the shaft, by the estimated gap feedback, can be levitated within $\pm$6 ${\mu}m$ positioning error.

• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.259-259
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• 2017

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.264-264
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• 2017