• 한국자동차공학회논문집
• /
• 제14권6호
• /
• pp.160-170
• /
• 2006

If hydraulic pump controlled by mechanical type regulator has more than one control function, the construction of regulator will be very complicated and control performance falls drastically. It is difficult to have more than one control function for hydraulic pump controlled by electronic type hydraulic valve due to the inconsistency of controllers. This paper proposes a multi-function control technique which controls continuously flow, pressure and power by using EPPR(Electronic Proportional Pressure Reducing) valve in swash plate type axial piston pump. Nonlinear mathematical model is developed from the continuity equation for the pressurized control volume and the torque balance for the swash plate motion. To simplify the model we make the linear state equation by differentiating the nonlinear model. A reaction spring is installed in servo cylinder to secure the stability of the control system. We analyze the stability and disturbance by using the state variable model. Finally, we review the control performances of flow, pressure and power by tests using PID controller.

• 드라이브 ㆍ 컨트롤
• /
• 제11권4호
• /
• pp.53-60
• /
• 2014

This paper proposes a control scheme to reduce the power consumption of a variable displacement swash-plate type piston pump supplying oil to a valve-controlled hydraulic cylinder at constant pressure. Whenever flow rate demand was absent, the swash plate angle and the pump speed were changed to the minimum values required to compensate for the internal leakage flow. In response to command signals, the pump speed was changed in proportion to the absolute mean value of the speed component for position commands. At the same time, a pressure regulator was activated to maintain constant system pressure by precisely adjusting the pump speed with the swash plate angle fixed at the maximum. The conventional system consisting of a pressure-compensated variable displacement type pump is driven at a constant speed of 1,800rpm. By comparison, computer simulation and experimental results showed that idling power at stand-by status could be reduced by up to 70% by reducing the pump speed from 1,800rpm to 300rpm and the swash plate angle to the minimum.

• 상하수도학회지
• /
• 제22권1호
• /
• pp.149-157
• /
• 2008

The reduction of leakage is a major issue of the South Korea water industry. The inclusion of pressure dependent leakage terms in network analysis allows the application of optimization techniques to identify the most effective means of reducing water leakage in distribution networks. This paper proposes a method to find optimal setting and location of control valve for reducing leakage efficiently. The proposed search method differs from previous methods for addressing optimal valve location problem and improves the GA simulation time with guaranteeing for getting the global optimal solution. The strength of this method has been demonstrated by means of case studies. This allows the procedure of optimization to be more robust and computational efficient.

• 한국산업융합학회 논문집
• /
• 제25권1호
• /
• pp.131-139
• /
• 2022

The exchange of goods over the sea is a situation in which the amount of trade between countries is gradually increasing. In order to maintain the optimal operating condition, the ship maintains stability and optimal operating conditions by inserting or withdrawing ballast water from the ballast tank according to the loading condition of cargo capacity is also increasing. Control valves play an important role in controlling fluid flow in these pipes. When the flow rate is controlled using a control valve, problems such as cavitation, flashing, and suffocating flow may occur due to high differential pressure, and in particular, damage to valves and pipes due to cavitation is a major problem. Therefore, in this study, the cavitation phenomenon is reduced by installing orifices at the front and rear ends of the high differential pressure control butterfly valve to reduce the sudden pressure drop at the limiting part of the butterfly valve step by step. The flow coefficient according to the shape of the orifice, the degree of cavitation occurrence, and the correlation were analyzed using a CFD(Cumputational Fluid Dynamics), and an optimal orifice design for reducing cavitation is derived.

• 한국자동차공학회논문집
• /
• 제3권6호
• /
• pp.123-133
• /
• 1995

An injection control valve(ICV) was designed to control the fuel flow between a common rail and an injector with two commercial solenoids. To improve the performance of ICV, the characteristic method was applied. With this method, the flow characteristics in the ICV and the injector were studied and the parameters which affect the injection characteristics were also studied. From this study, following results were obtained. The injection duration can be controlled and with modifications of the effective valve stroke of ICV, the injection quantity and duration can be reduced to desired amount. Also the injection quantity and pressure can be controlled by reducing the hole size of the injector without the variation of the injection duration. For some conditions, the desired injection characteristics can be obtained by the changes of the valve timing, the effective valve stroke, the open pressure of the injector and the hole size of the injector.

• 한국정보통신학회논문지
• /
• 제7권5호
• /
• pp.1026-1031
• /
• 2003

자동 급수펌프는 압력스위치에 의해 운전 및 정지를 하게 된다. 따라서 수량 증감에 따른 펌프의 빈번한 운전 및 정지로 인해 지속적인 정격 및 정압 운전이 불가능하다. 또한 빈번한 작동으로 인해 지속적으로 일정한 압력을 얻을 수 없으며, 펌프의 소손과 에너지의 낭비가 심한 단점을 가지고 있다. 본 논문에서는 이러한 단점을 해결하고자 급수밸브, 유량센서, 제어장치로 구성되는 정압 급수장치를 설계 제작하였다. 급수밸브는 유출되는 물의 양과 관계없이 항상 일정한 양의 물을 유입하여 펌프의 부하를 줄이는 역할을 한다. 유량센서는 적외선 다이오드를 사용하여 유출되는 물의 양의 측정하며, 제어장치는 8 비트 마이크로프로세서를 이용하여 설계하였으며, 특별한 제어 알고리듬에 의해 펌프의 운전과 정지를 제어하게 하였다. 본 논문에서 개발한 장치는 토출 압력이 일정하게 유지되고 펌프의 작동 및 정지 동작이 부드럽게 이루어지며, 펌프의 지속적인 정압운전이 가능하므로 기존의 단점을 보완하는 장치로 사료된다.

• Journal of Advanced Marine Engineering and Technology
• /
• 제28권2호
• /
• pp.269-276
• /
• 2004

A marine diesel engine should realize optimal efficiency operation while reducing NOx. Fuel injection systems by electronic control can become effective means for that. Although it would be able to get more precise engine control compared to the mechanical injection system, it needs some accurate and instant information in order to bring its ability into full play while sailing on the sea. Very important information of them is shaft torque and continuous combustion pressure of all cylinders. The system presented in this report can deliver those data.

• 한국산업융합학회 논문집
• /
• 제4권3호
• /
• pp.305-310
• /
• 2001

Hydraulic power shifting systems of hydraulic travel motor may be far safer than mechanical power transmission systems. Thus, hydraulic power shifting systems are widely used for speed control on the hydraulic equipments. In the case of liquid shifting lines, the rapid change of area, such as valve closing, can result in a large pressure transient. It is necessary to assure proper control method in order to obtain the smallest shift shock. This study conducts the shock characteristics of hydraulic power shifting system of the hydraulic travel motor. Experimental results show that shock pressure depends on the operating pressure, flow rate and pipe line area. The shock characteristics can be applied for reducing shocks.

• 중환자간호학회지
• /
• 제4권1호
• /
• pp.37-50
• /
• 2011

Purpose: This study is to evaluate the effect of abdominal breathing on postoperative pain, state anxiety, blood pressure, and heart rate of cardiac surgery patients treated in intensive care unit. Methods: A non-synchronized design of nonequivalent control group pre-post test was used. Participants were divided into an experimental group(n=22) and a control group(n=21). Just usual postoperative treatments were provided to the control group, while abdominal breathing interventions were provided to the experimental group, in addition to usual treatments. The intervention was consisted of 4 stages-introductions, breathing perception, breathing training, and closing-and it lasted twelve minutes in total. Pain, state anxiety, blood pressure and heart rate were the dependent variables of the abdominal breathing. Results: Those who carried out abdominal breathing showed a significant reduction in pain, as well as decrease of systolic blood pressure. However, it turned out to have no effect on state anxiety, diastolic blood pressure and heart rate. Conclusion: Abdominal breathing is simple and harmless and is effective for reducing postoperative pain.

• 성인간호학회지
• /
• 제20권1호
• /
• pp.55-64
• /
• 2008

Purpose: The purpose of this study was to identify the effect of Meridian pressure on the functions of upper extremities and discomfort of ADLs of hemiplegic patients. Methods: The research design was a nonequivalent control group, non-synchronized design. Subjects were 35 hemiplegic patients who were hospitalized at L Oriental Medical Hospital; 18 for the experimental group and 17 for the control group. The experimental group was given meridian pressure for 10 minutes daily for 2 weeks. The data were analyzed by SPSS 12.0 program. The ${\chi}^2$-test and t-test were used for the two groups' homogeneity, and t-test was used for the hypothesis test. Results: Manual muscle test, ROMs of wrist extension, elbow flexion, and shoulder extension of the experimental group increased compared to the control group. Shoulder pain and index finger circumference of the experimental group decreased compared to the control group. The experimental group showed to have less discomfort of ADLs than the control group. Conclusion: The study results verified that meridian pressure is effective for improving the functions of hemiplegic patients' upper extremities as well as reducing discomfort of ADLs.