• The KSFM Journal of Fluid Machinery
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• v.3 no.4 s.9
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• pp.52-58
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• 2000

The numerical study on the waterhammer was carried out for the intake pumping station of the metropolitan water supply 6th stage project. Because the waterhammer problems as a result of the pump power failure were the most important, these situations were carefully investigated. The surge tank and the stand pipes effectively protected the tunnels md the downstream region of pipeline from the pressure surge. In case the moment of inertia of the pump and motor was above $5080\;kg{\cdot}m^2$, the column separation did not occur in the pipeline between the pumping station and the inlet of 1st tunnel. As the moment of inertia increased, the pressure surges decreased in the pipeline conveying raw water. The pump control valve was chosen as the main surge suppression device for the intake pumping station. After power failure, the valve disc should be rapidly closed in 2.5 seconds and controlled the final closure to 15 seconds by the oil dashpot. If the slamming happened to the pump control valve, there was some danger of this system damaging. As the reverse flow through the valve increased, the upsurge extremely increased.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.40-50
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• 2016

In order to recover the power system during the wide power outage or power failure in the power plant, black start system should be properly operated without any problem. Especially power for black start in the geographically isolated areas of electric island is supplied from small emergency start-up generator, and loads are aux systems of gas turbines such as SFC(Static frequency converter). This paper introduces the international practices to overcome the voltage drop problem with harmonics of the system having the DC output such as SFC during black start in weak feed system and analyzes the relationship between house load inputs and harmonics. By varying the house load and input of power supply, this paper identified boundaries between weak feed and strong feed power. In order to verify the theory of stable condition in weak feed power system with DC output, house load is simulated using ETAP. Additionally MATLAB was used for harmonic analysis between the load inertia moment and non load inertia moment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1801-1809
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• 2000

A study on the topology optimization of Hard-Disk-Driver(HDD) actuator arm in free vibration is presented. The purpose of this research is to increasse the natural frequency of the first lateral mode of the HDD actuator arm under the constraint of total moment of inertia, so as to facilitate the position control of high speed actuator am. The first lateral mode is an important factor in the position control process. Thus the topology optimization for 2-D model of the HDD actuator arm is considered. A new objective function corresponding to multieigenvalue optimization is suggested to improve the solution of the eigenvalue optimization problem. The material density of the structure is treated as the design variable and the intermediate density is penalized. The effects of different element types and material property functions on the final topology are studied. When the problem is discretized using 8-node element of a uniform density, the smoothly-varying density field is obtained without checker-board patterns incurred. As a result of the study an improved design of the HDD actuator arm is suggested. Dynamic characteristics of the suggested design are compared computationally with those of the old design. With the same amount of the moment of inertia, the natural frequency of the first lateral mode or the suggested design is subsequently increased over the existing one.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.9
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• pp.813-821
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• 2000

In this paper, we developed modeling of tension and speed dynamics for a two-drum winder in a three span continuous web transport system which had not been previously. Dynamic modeling of the time-varying nonlinear system was derived by considering the effect of the radii and mass moment of inertia in the unwinder and the two-drum winder through winding up the web. After linearizing it, we designed with a variable-gain a PID controller for tension control and a PI controller for speed. Simulation is carried out with the variation of radii and moment of inertia at high speed for the proposed tension control system with the two-drum winder and the variavle-gain a PID controller. Results show good performance of tension control during the speed change speed at a start-up and stop.

• Proceedings of the KIPE Conference
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• 2004.11a
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• pp.18-20
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• 2004

In this paper, a new technique of inertia identification using recursive least square algorithm and full order estimator is proposed. The speed response is sensitive to variation in machine parameters especially the moment of inertia. The effectiveness of the method has been verified by simulations.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.1
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• pp.24-31
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• 2004

Recently, as the marine compressor power is increased, vibration problems on the marine vessel with V/W type reciprocating compressor have been occurred. A research on the balancing of marine V/W type reciprocating compressor has hardly been reported though a number of researches on the balancing of rotating machinery have been conducted. As a V/W type compressor has high capacity with long stroke, compact size and high center of gravity, It is easy to have a vibration problem by a little bit unbalanced force and moment. In this study, calculation methods for balance weight of the V/W type reciprocating compressors, which have different piston weight and asymmetry structure, are formulated. And their reliability were verified by comparing calculated balance weight with the experimental results of the real marine V/W type reciprocating compressors.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.283-286
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• 2004

This work presents a 3-axis active mount featuring the piezoelectric stack actuators. The inertia configuration for the piezoelectric actuators is adopted to achieve appropriate force and moment in each axis. In addition, the rubber mount is integrated to provide stiffness for system loading. In order to analyze the active mount, the governing equation for the force and moment is derived and its validity is demonstrated by comparing generated force and moment of each actuator between analysis and experiment. In addition, the natural frequency of each actuator is identified though both simulation and experiment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.9 no.4
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• pp.1-8
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• 1989

The main purpose of the present paper is to present both the fundamental frequency and some higher free vibration frequencies for circular arches with variable section, in which rotatory inertia is included. The differential equations are derived for the in-plan free vibration of elastic circular arches with variable section. These equations were solved numerically for the linear variable circular cross-section with clamped-clamped end constraint. As the numerical results, the four lowest nondimensional natural frequencies presented as functions of the nondimensional system parameters : the end moment of inertia to crown moment of inertia ratio, the slenderness ratio, and the opening angle. The effect of rotatory inertia on the nondimensional natural frequency is also reported.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.5
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• pp.467-477
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• 2004

A new scheme to estimate the moment of inertia in the servo motor drive system in very low speed is proposed in this paper. The typical speed estimation scheme in most servo system for low speed operation is sensitive to the variation of machine parameters, especially the moment of inertia. To estimate the motor inertia value, the observer using the Radial Basis Function Networks(RBFN) is applied. The effectiveness of the proposed inertia estimation method is verified by experiments. It is concluded that the speed control performance in the low speed region is improved with the proposed disturbance observer using RBFN.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.17 no.1
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• pp.1-8
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• 2009

In this paper, reorientation based on angular momentum exchange is applied for a bias momentum stabilized satellite, which is equipped with a spherical fuel tank, and the effect of liquid slosh on the attitude properties such as inertia tensor and angular rate is investigated. In order to represent the slosh motion of liquid an equivalent mechanical model is adopted and full nonlinear equations of motion for three-body system are derived. Computer simulations are performed for several cases, which use the viscosity of liquid and the center location of the tank as input parameters, mainly in order to observe how the viscosity of liquid and the center location of the tank influence the spacecraft’s attitude. The investigation includes observing time-variations of the inertia tensor, especially presence of components of product of inertia during the maneuver.