• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.140-147
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• 2001

The solenoid valve in ABS hydraulics, modulator is a two directional on-off valve and is controlled by around 100Hz high speed pulse width modulation. When the inlet valve is switched from open state to closed state, there are braking force degration, noise and vibration due to pressure surge phenomena in the hydraulic line and wheel cylinder. In this study, identifies pressure surge phenomenon in the braking process of a ABS, and investigates the way to reduce the phenomenon. For the purpose theoretical analysis on the pressure surge in the closed state hydraulic line, characteristic curve method based on wave equation was utilized. During this analysis, we could find pressure surge characteristics change due to hydraulic line change and PWM control conditions. In conclusion, by using the results of this study for the pressure surge prediction and reduction method, we could expect braking performance enhancement in Anti-Lock Braking System.

• The KSFM Journal of Fluid Machinery
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• v.17 no.3
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• pp.65-70
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• 2014

The effectiveness of a perforated plate installed additionally at butterfly valve to reduce cavitation which can cause vibration, noise, erosion, and flow path blockage has been investigated using CFD. Rayleigh-Plesset equation was applied to simulate cavitation phenomena. 3D flow simulations have been performed for 6 cases to consider the occurrence of cavitation at the downstream of the valve. From the present results, the perforated plate was thought to be very effective to suppress the cavitation inside of the pipe.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.3
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• pp.109-114
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• 2008

The solenoid valve of ABS hydraulic modulator is a two directional on-off valve and is controlled by around 100Hz on-off control. When the on-off valve is switched from open state to closed state, there are braking force deterioration, noise and vibration due to surge pressure in the wheel cylinder. In this study, identifies surge pressure in the braking process of ABS, and investigates the way to reduce the phenomenon. To reduce the surge pressure, PWM(Pulse Width Modulation) control with high frequency of 20kHz was attempted. In conclusion, by using the results of this study for the pressure surge prediction, we could expect enhancement of braking performance in ABS.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.109-116
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• 1998

This paper is concerned with effective operating method of pneumatic on-off valves for improving position control accuracy, valve life-time and position settling time using modified pulse width modulation with dead-zone (MPWMD). The pneumatic system using on-off valves has advantage of simple construction and low cost compared with a system with servo-valves. The performance of the proposed control method is investigated experimentally for the position control of a pneumatic cylinder using on-off valves. Experimental results show that the proposed algorithm for valve operation can be used to obtain fast and accurate position control compared to the conventional PWMD algorithm. It is also shown that the use of the proposed MPWMD algorithm for the position control significantly reduces the number of valve switching and noise.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.75-81
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• 1998

It is very important to evaluate the friction force of valve train system in the aspect of reducing friction loss of engine. To this end, we have developed measuring system of friction force of engine valve train system. There were two major factors in the process of development of it. One was it had to accurately measure the friction force up to 3500 Crpm without any problems such as mechanical vibration, electrical noise and so on. The other was it also had to simulate real engine conditions such as Crpm, oil temperature, oil pressure and oil aeration including effect of belt drive system. In this paper we have introduced the process of development of it based on test results, and also analysis process of measured data.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.75-78
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• 1997

In this paper we present new sound spectral analysis methods or prosthetic heart valve sounds. Phonocardiograms(PCG) of prosthetic heart valve were analyzed in order to derive frequency domain feature suitable or the classification of the valve state. The fast orthogonal search method and MUSIC (MUltiple SIgnal Classification) method are described or finding the significant frequencies in PCG. The fast orthogonal search method is effective with short data records and cope with noisy, missing and unequally-spaced data. MUSIC method's key to the performance is the division of the information in the autocorrelation matrix or the data matrix into two vector subspaces, one a signal subspace and the other a noise subspace.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.411-415
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• 2007

The reduction of airborne and structure-borne noise of a shipboard pump for a navel ship is very important because the noise levels of the pump must not exceed criteria such as MIL-STD. In this paper, several practical examples of reducing the noise levels are presented. The examples show that the inadequate rotor-balancing and shaft-alignment results in the increase of the structure-borne noise on all lower mounts. It is also found that the unequal loading on mounts can cause the dramatically increasing the noise levels on certain local positions. Since the piping system arrangement such as valve location, flexible joint, and elbow location affects on the noise measurement, care must be taken to minimize the unnecessary noise from the piping system.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3383-3388
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• 2007

To compare the sensor performance of AE leak diagnosis system which can measure valve leak conditions, AE activities such as RMS voltage level, AE signal trend, leak rate degree according to AE database, FFT spectrum were measured on valve of the simulated test system for power plant. AE activities were recorded and analyzed from various operating conditions including different temperature, pressure difference, valve size and fluid using both piezoelectric acoustic emission sensor and Pb-Free acoustic emission sensor. The results of this study are utilized to select the type of sensors, the frequency band for filtering and thereby to improve the signal-to-noise ratio for diagnosis or monitoring of valves in operation. As the final result of application study above, portable type leak diagnosis system by AE was developed. The outcome of the study can be definitely applied as a means of the diagnosis or monitoring system for energy saving and prevention of accident for power plant valve.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.133-138
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• 2011

Compression pressure of individual cylinder and valve timing have big influence on combustion pressure, indicated mean effective pressure (IMEP), emission, vibration, combustion noise and many other combustion parameters. Therefore, uniformity of compression pressure and valve timing became one of most important engine design and production standard. Conventional method to evaluate compression pressure uniformity is to measure each cylinder pressure by mechanical pressure gage during cranking. This conventional method causes inaccuracy of cylinder pressure measurement because of different cranking speed results from battery status and also causes high manhour and cost. To check valve timing, related FEAD parts should be disassembled and timing mark should be checked manually. This study describes and suggests new methodology to measure compression pressure by analysis of start motor current and to check valve timing by cylinder pressure with high accuracy. With this new methodology, possibility to detect leaky cylinder and wrong valve timing was observed.

• Transactions of The Korea Fluid Power Systems Society
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• v.4 no.4
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• pp.1-7
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• 2007

Flow rate is one of the important variables for precise motion control and detection of the faults and fluid loss in many hydraulic components and systems. But in many cases, it is not easy to measure it directly. The orifice area of a servo valve by which the fluid flows is one of key factors to monitor the flow rate. In this paper, we have constructed an estimation algorithm for the effective orifice area by using the model of a servo valve cylinder control system and Kalman filter algorithm. Without geometry information about the servo valve, it is shown that the effective orifice area can be estimated by using only displacement and pressure data corrupted with noise. And the effect of the biased sensor data and system parameter errors on the estimation results are discussed. The paper reveals that sensor calibration is important in accurate estimation and plausible parameter data such as oil bulk modulus and actuator volume are acceptable for the estimation without any error. The estimation algorithm can be used as an useful tool for detecting leakage, monitoring malfunction and/or degradation of the system performance.