• Tribology and Lubricants
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• v.18 no.2
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• pp.99-104
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• 2002

The paper presents the unbalance response of a rotor-bearing system supported by an active control bearing. The proportional, derivative and integral controls are investigated fur the control algorithm of an active control bearing to suppress the unbalance response of a rotor-bearing system. Results of analytical investigations on the unbalance responses of a rotor supported by an active control bearing are presented for various control gains. It is found that the unbalance response of a rotor can be greatly suppressed by the proportional, derivative or integral control of the bearing. The proportional control is more effective than the derivative control at low rotational speed, and the derivative control is more effective than the proportional control at high rotational speed. In the case of the integral control of the bearing, the unbalance response ova rotor is increased as a general rule. However, the integral control of the bearing is extremely superior to proportional or derivative control at very low rotational speed.

• 제어로봇시스템학회:학술대회논문집
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• 1989.10a
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• pp.766-771
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• 1989

The authors tried to make experimentally clear the response of engine speed to stepwise increasing, decreasing or sinusoidally fluctuating load. Based on a simplified model devised from the standpoint of the control theory, analysis was carried out with digital computer and its results obtained coincide well with those of experiment, so that it could be confirmed that it is possible to simulate the speed response to variation of the load.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.2
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• pp.79-86
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• 1995

Frequency response method is used to design hydraulic servo systems and improve its performance. In this study a method is proposed to get simply the frequency response of the electro-hydraulic servo system which use PWM controlled high-speed on-off valves. Firstly, the describing function of the PWM element is derived and tested. It is found that the character- istic of PWM element could be approximated to a saturation characteristic in the range of allowable frequency. And the dynamic characteristic of the valve-cylinder system could be negligible. The working characteristic of high-speed on-off valve is considered as time delay. So simulation is performed in the basis of the reconstructed block diagram. And this method is verified by experiments.

• Journal of the Ergonomics Society of Korea
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• v.25 no.4
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• pp.129-135
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• 2006

he purpose of this study is to measure bio-signal to investigate the driver's physiological response change under real situation using train simulator. The train simulator used in this study is KTX model and according to changes of driving situation, The bio-signal controlled by autonomic nervous system, such as GSR(Galvanic Skin Response), SpO2(Saturation percent O2), HR(Heart Rate), ECG(Electrocardiograph), EEG(Electroencephagram) and movement and response of eye were measured. Statistically significant difference in bio-signal data and eye movement activity pattern were investigated under several different driving speeds using analysis of variance (p<0.05). The GSR and HR value measured in average and mission speed operation is higher than in high-speed operation. β wave of EEG in average speed operation become more activated than in high speed operation. In accordance with a characteristic of rail vehicle, movement and response of eye in high-speed operation requiring relatively simple maneuver become less activated than in either average or mission speed operations. Conclusively, due to more careful driving controls in average and mission speed operation are required than in high-speed operation, level of mental and physical stresses of train driver was increased and observed through changes of bio-signal and eye movement measured in this study.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.477-485
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• 2007

When Korean High Speed Train (KTX) runs over a high-speed railway bridge, the high-speed railway bridge gives quite large acceleration response. Local vibration at the large cross section, the impact from equally spaced sleepers, the vibration due to elastomeric bearings, and the vibration from the train itself are the causes of this acceleration response. Maximum peaks of the accelerations measured at the bridges are sometimes going over the limit value. Although it is smaller than 0.35G, the limit from the Korean Bridge Design Manual(BRDM), this acceleration response should be reduced for the safety of running trains with high speed. In this paper, to reduce the acceleration response by controlling excessive local vibration at the large cross section, vibration reduction method is studied. The result shows that the effect of elastomeric bearings on the vibration of the bridge is very large and that the vibration reduction device is effective against wing mode local vibration PSC box girder bridge for the high-speed railway, which usually has very large cross section, although it has little effect on global vibration modes such as flexural and twisting modes. The test of the vibration reduction device on the bridge in service has been performed in this study.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.1
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• pp.38-44
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• 2009

Recently, the research focused on fuel cell hybrid vehicles (FCHVs) is becoming an attractive solution due to environmental pollution generated by fossil fuel vehicles. The proper energy control strategy will result in extending the fuel cell lifetime, increasing of energy efficiency and an improvement of vehicle performance. Battery state of charge (SoC) is an important quantity and the estimation of the SoC is also the basis of the energy control strategy for hybrid electric vehicles. Estimating the battery's SoC is complicated by the fact that the SoC depends on many factors such as temperature, battery capacitance and internal resistance. In this paper, battery charging time estimated by SoC is studied by using the speed response and current response. Hybrid system is consist of a fuel cell unit and a battery in series connection. For experiment, speed response of vehicle and current response of battery were determined under different state of charge. As the results, the optimal battery charging time can be estimated. Current response time was faster than RPM response time at low speed and vice versa at high speed.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1993.06a
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• pp.933-936
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• 1993

A high speed fuzzy processor using bipolar technology is proposed in this paper. The hardware system uses a high-speed current-mode membership function circuit and normalization technique. The new membership function circuit generates an ideal membership function of the fuzzy set and its circuit is also simple and available for VLSI implementation. Several techniques have been implemented to speed up response of the processor. The fuzzy processor has been designed and implemented in bipolar circuit technology. The experiments and simulations show that the response speed is below 100ms. It can also be expected that the fuzzy processor can be integrated on one chip and its response time is only about the order of nanoseconds.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.38 no.3
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• pp.166-172
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• 1989

The model reference adaptive control algorithm (MRAC), which is one of the methods for controlling the speed of a permanent magnet synchronous motor (PMSM), has been developed using the autoregressive (ARMAX) method. Applying this algorithm to a microprocessor which is used in driving PMSM with PI controller, it has been proved that the response speed of the reference input follows closely that of the reference model. It has also been proved by experiments that the quick speed response without over-shoot could be obtained for the motor system with variable parameters.

• Journal of the korean society of oceanography
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• v.31 no.4
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• pp.183-195
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• 1996

A barotropic non-linear numerical model is used to study the response of the Yellow Sea to winter cyclone passage. Cyclones normally come from the outside of the western boundary, China, and pass the region eastward. The cyclone parameters used for the present study are the following: the intensity, i.e., the maximum wind speed of the cyclone; the effective radius corresponding to this maximum; and the translation speed. The equations of motion are integrated over the depth which is supposed to be a constant. The Gaussian function is used to define the stream function of the wind. The following results have been found. A northward current is generated by the frontal part of the cyclone near the western boundary. After the cyclone leaves the sea area, a southward current is generated by the rear part of the cyclone. After that, a northward current is generated once again due to the westward propagating Rossby waves. The response of the sea to the cyclone passage is strongly influenced by a steady current when the steady current and the current due to the cyclone wind are of the same order. The steady current diminishes the sea response and reduces the speed of the southward current, and enhances the northward current speed. The intensity and the translation speed of a cyclone also influence the flow pattern significantly.

• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.35-42
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• 2010

This paper deals with the development of analytical model of a turbocharger and its detail rotordynamic analysis. Two analytical models, which are verified by experimental modal testing, are proposed and the analytical model including rotor shaft extended to compressor and turbine wheel end side is chosen. A rotordynamic analysis includes the critical map, Campbell diagram, stability, and unbalance response, especially nonlinear transient response considering nonlinear fluid film force at bearings. Although the linearized analysis accurately predicts the critical speeds, stability limit, and stability threshold speed, the predicted vibration results are not valid for speeds above the stability threshold speed since the rotor vibrates with a subsynchronous component much larger than the one synchronous with rotor speed. Hence, for operating speed above the stability threshold, a nonlinear transient analysis considering nonlinear fluid film force must be performed in order to accurately predict vibration responses of rotor and guarantee results of analysis.