• 한국자동차공학회논문집
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• 제21권5호
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• pp.169-175
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• 2013

CRDi technology of diesel engine was developed from in the early 2000s due to a need to increase fuel efficiency and environment care. Especially, high-pressure fuel injection system in CRDi system which has a fuel injection unit including an injector, a fuel pump and common-rail, etc. becomes possible to make the exhaust gas clean as well as power improvement. In this study, comparison of dynamic characteristics of servo-hydraulic piezo-driven injector with 3-way and bypass-circuit type was analyzed by using the AMESim code. As results of this study, it found the bypass-circuit inside servo-hydraulic piezo injector can cause a faster injection response than that of the 3-way type. Also it was shown that bypass-circuit type had better control capability due to hydraulic bypass system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1998년도 제13차 학술회의논문집
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• pp.474-479
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• 1998

In this paper, we present a mathematical model of the piezoelectric pump and its application to the automobile brake system. The piezoelectric pump consists of a multi-layered piezoelectric element a diaphragm, pumping values, resonant pipes and accumulators, and the maximum pumping power of 62W nab obtained in the previous experiments by using the piezoelectric element of 22mm diameter and 55.5mm length. A detailed mathematical model of the pump is derived here by considering the compressibility of the working oil, nonlinear characteristics of piezoelectric element, the time delay of pumping values' action and be on. The validity of the model is illustrated by comparing the experimental data and the simulation results. Using the mathematical model of the piezoelectric pump, a brake system for automobile disk brake is also simulated in this paper. The brake system consists of a piezoelectric pump as a power source, calipers and its piston to generate brake force, and a three position solenoid value to change the brake situation. It is shown that 15mm/sec of piston speed and 20kN of piston force are obtained by using the piezoelectric element of 33mm diameter and 55.5mm length.

• 대한기계학회논문집
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• 제17권8호
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• pp.2023-2032
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• 1993

This study suggests a new type shaft generating system driven by hydrostatic transmission suitable for small size vessels. Since the shaft generating system is affected ceaselessly by disturbances such as speed variation in pump driving speed and variation in external load, a robust servo control must be implemented to obtain stable electric power with constant frequency. Thus, in this study, a digital robust servo control algorithm is applied to the controller design. By the experiment and the numerical computation, the frequency variation characteristics of the generating system under various disturbances are investigated. Conclusively, it is said that the shaft generating system proposed in this study shows excellent control performances.

• Journal of Mechanical Science and Technology
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• 제19권8호
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• pp.1621-1631
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• 2005

In this paper, making the best use of the features of the electro-rheological (ER) valve, a two-port pressure control valve using ER fluids is proposed and manufactured. The ER-Valve characteristics are evaluated by changing the intensity of the electric field and the number of electrode. As only with electrical signal change to the ER-Valve in which ER fluid flowing, ER fluid flow is controlled, so development of simple ER-Valves have been tried. The ER-Valves and pressure drop check method are considered to be applied to the fluid power industry. Using the manufactured pressure control valve, a one-link manipulator with FHA (Flexible Hydraulic Actuator) is driven. As a result, it is experimentally confirmed that the pressure control valve using ER fluids is applicable to use in driving actuator. If it applies characteristics of the ER fluids, it will be able to apply in the control system for the ER Valve which occurs from industrial controller. After having durability test, shear stress increased regularly because of starch particles crushed by pump and particle size that was almost the same. Moreover, Ra of copper electrode increased about 1.56 times rather than before those of performing durability test, and Rz increased about 2.2 times.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1261-1265
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• 2003

Axial piston pumps of bent axis have been commonly used in hydraulic systems because of high pressure level. best efficiency, low shear force on pistons and low operating costs. The other side, they have a few demerits like that they have the relatively high number of moving parts and more discharge pressure ripples. Especially, the discharge pressure ripples bring about vibrations and noises in hydraulic system components such as connecting pipes and control valves, so that these deteriorate the stability and accuracy of the systems. Therefore, the hydraulic systems having the axial piston pumps of bent axis require the methods to reduce the discharge pressure ripples. So, the purpose of this paper is to reduce the discharge pressure ripples by the phase interference of pressure wave and to develope the analysis model of the pumps to predict the discharge pressure ripples. In this paper, the analysis model of the axial piston pumps of bent axis was developed using the AMESim software, and the reliability of that was verified by the comparison with the experimental results. The hydraulic pipeline with a parallel line was used as the method to generate the phase interference of pressure wave. the dynamics characteristics of the hydraulic pipeline with a parallel line were analyzed by a transfer matrix method. the usefulness of the phase interference of pressure wave was investigated through the experiment and simulation. The results from the experiment and simulation said that the phase interference of pressure wave by the hydraulic pipeline with a paralle linel could reduce the discharge pressure wave of the pump well. The analysis model of the axial piston pumps of bent axis developed in this paper and the method of the phase interference by the hydraulic pipeline with a parallel line are expected to be helpful to achieve the design of the pump and to reduce the discharge pressure wave of the pump effectively.

• 드라이브 ㆍ 컨트롤
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• 제16권1호
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• pp.14-21
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• 2019

Axial piston pump is a significant part in wheeled armored vehicle, for generating hydraulic power of vehicle power system. The Axial Piston Pump is a high-performer, core functional item that is developed and applied to most of the military models in the development of military weapon systems. However, in the case of military equipment, there are conditions of limited size and weight required depending on the operating conditions and the operating environment. Under these conditions, it is required that the performance and the environmental resistance are verified to exert the required output. A unique technology is needed for the development of such equipment both in the present and in the future. Therefore, in this study, mathematical modeling of an axial piston pump is presented as a basic data for securing proprietary technology. In addition, a simulation model is designed and compared with the models of six kinds of pistons through simulation. It was established that when the number of pistons of the axial piston pump, which is the development objective, is seven, the model is suitable for the wheeled armored vehicle.

• Tribology and Lubricants
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• 제30권3호
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• pp.183-188
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• 2014

In this paper, we present our analysis of tribological failure examples for an anti-lock brake system(ABS) in a car. The study range of this paper is to improve the quality of ABS system by analyzing with sensor, computer, actuator and oil lines. In the first example, the brake leak from hydraulic supply line in a caliper on the rear left side of the ABS hydraulic modulator. This produces the sponge phenomenon, where the car does not brake even when the driver operates the brake pedal. The hydraulic unit operating ABS is actuator that play role regulating drive condition according with the oil pressure supplied with wheel of a car. In the second example, the service man does not completely tighten the fixed bolt after repairing the car. This causes the ABS warning lamp to light up as the ABS wheel speed sensor cannot detect whether the ABS has been activated. In the third example, the ABS electronic control unit is separated from the soldered part of the inner circuit board. Consequently, the ABS fails in control because the ABS motor pump receives no-signal for the hydraulic unit. The wheel speed sensor has to large durability because of giving signal of acting condition to computer by detected the acceleration and deceleration of wheel of a car. In the fourth example, the ABS warning lamp lights up of when cracks propagate in the circuit board soldering part. The circuit of this computer is very important part for input and output the operating signal of system. Such failures can aggravate the durability of the ABS. Thus, the ABS needs to be optimized to eliminate malfunction phenomenon.

• 물과 미래
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• 제12권2호
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• pp.49-55
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• 1979

본 연구는 관수로내의 부정류 즉 펌푸모터의 시동, 정지 및 발브 조절시에 압력관수로에 나타나는 급변류의 현상, 특히 수격작용의 해석을 Computer에 의해 자동해석하는 방법을 강구하였다. 따라서 사용되는 관수로가 펌푸, 관망, 터널, 조압수조, 분기관, 저수지, 폐단관 및 발브장치를 갖는 일련의 관수로내에 일어나서 전자계산기를 사용하면 송수 또는 배수관로 설계에 있어 설계자의 시간과 노력을 감소하고 정확한 결과를 얻을 수 있는 장점이 있다.

• 드라이브 ㆍ 컨트롤
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• 제18권2호
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• pp.1-8
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• 2021

In this work, a circuit with a hydraulic power unit is formulated as a means of predicting the behavior of the prefill valve in the future. The behavior of the prefill valve can be examined by the measurements of the configured power unit, and the performance is determined by using hydraulic pumps, relief valves, and hydraulic hoses that make up the power unit. In particular, pressure/flow pulsation generated by hydraulic pumps can cause instability in the prefill valve and cause noise-induced degradation of the overall performance and reliability of the hydraulic system containing the prefill valve. Therefore, to study the behavior and performance of the prefill valve in a relatively accurate manner, the prediction of the characteristics of the hydraulic power unit driving the prefill valve is very important. In this study, the pulsation characteristics of the hydraulic pump were analyzed to theoretically demonstrate its relationship with different settings of the power unit, such as relief valve pressure settings and the presence/absence of the hose.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.109-112
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• 2011

한국형발사체 추진기관 개발을 위한 연소기 연소시험설비와 터보펌프 실매질 시험설비의 배치 및 설계에 대해 간략히 기술하였다. 연소기 연소시험설비 및 터보펌프 실매질 시험설비에서 75톤급 액체로켓엔진의 부품인 연소기 및 터보펌프의 개발 및 인증시험을 수행할 예정이다. 연소기 및 터보펌프 시험설비의 유공압 설비, 제어계측 시스템, 시험 스탠드 그리고 부대설비에 대한 상세설계를 완료하였다.