• 제어로봇시스템학회논문지
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• 제6권3호
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• pp.329-337
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• 2000

This study describes a pressure tracking control of hydroforming process which is used for precision forming of sheet metals. The hydroforming operation is performed in the high-pressure chamber strictly controlled by pressure control valve and by the upward motion of a punch moving at a constant speed, The pressure tracking control is very difficult to design and often does not guarantee satisfactory performances be-cause of the punch motion and the nonlinearities and uncertainties of the hydraulic components. To account for these nonlinearities and uncertainties of the process and iterative learning controller is proposed using Cerebellar Model Arithmetic Computer (CMAC). The experimental results show that the proposed learning control is superior to any fixed gain controller in the sense that it enables the system to do the same work more effectively as the number of operation increases. In addition reardless of the uncertainties and nonlinearities of the form-ing process dynamics it can be effectively applied with little a priori knowledge abuot the process.

• Journal of Advanced Marine Engineering and Technology
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• 제38권10호
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• pp.1225-1231
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• 2014

This paper presents the performance characteristic of a Francis hydro turbine with an inline casing. This turbine is designed for city water supply system. Due to large changes in ground elevation with high points and low points, some systems may experience larger-than-normal required pressures in areas with low ground elevations. One way to dissipate these excess pressures is by the use of an inline-turbine instead of an inline-pressure reducing valve. For best applicability and minimal space consumption, the turbine is designed with an inline casing instead of the common spiral casing. As a characteristic of inline casing, the flow accesses to the runner in the radial direction, showing a low efficiency. The installation of vanes improves the internal flow and gives the positive encouragement to the output power. For the power transmission to the outside of the turbine casing from the runner axis, a belt passage is designed in the inline casing, as its influence, the region after the belt passage shows a relatively low output power. The clearance gap in the runner side space is considered, in which a small volume of flow is contracted into the clearance gap, forming the leakage flow. The leakage flow leads to a decrease in the efficiency.

• Steel and Composite Structures
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• 제26권1호
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• pp.55-66
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• 2018

In this paper, the response of an underground fibreglass reinforced plastic (FRP) composite pipe system subjected to realistic loading scenarios that may be experienced by an actual buried pipeline is investigated. The model replicates an arbitrary site with a length of buried pipeline, passing through a $90^{\circ}$ bend and into a valve pit. Various loading conditions, which include effects of pipe pressurization, differences in response between stainless steel and fibreglass composite pipes and severe loss of bed-soil support are studied. In addition to pipe response, the resulting soil stresses and ground settlement are also analysed. Furthermore, the locations of potential leakage and burst have also been identified by evaluating the contact pressures at the joints and by comparing stresses to the pipe hoop and axial failure strengths.

• 한국항공우주학회지
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• 제36권7호
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• pp.695-702
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• 2008

액체 로켓 엔진의 연료 공급 시스템은 다양한 원인으로 인해 유동 불안정이 발생한다. 특히 연료 공급 시스템에서 발생하는 공동 현상은 공동의 생성과 소멸로 인해 후류 쪽의 압력 및 유량의 진동을 유발하게 된다. 액체 로켓은 주 추진제로 극저온 유체를 사용하게 되는데, 극저온 유체는 온도에 민감한 성질을 갖고 있기 때문에 공동 현상의 해석에 있어 온도 변화에 대한 효과를 반드시 고려해주어야 한다. 본 연구에서는 Shyy등이 제안한 “MUSHY IDM"모델을 이용하여 극저온 유체에서 발생하는 공동 현상을 모사하였다. 이를 바탕으로 오리피스에서 발생하는 공동 현상이 유동 불안정에 어떠한 영향을 미치는 지와 오리피스 형상 변화가 후류 유동의 불안정에 끼치는 영향을 연구하였다.

• 대한기계학회논문집B
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• 제22권11호
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• pp.1530-1537
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• 1998

Mixture formation is one of the significant factors to improve combustion performance of an spark ignition engine. This is affected by spray and atomization characteristics of injector. In the case of EGI system, air-fuel mixing period is so short that a lot of fuel-film and liquid-fuel flow into cylinder. Since this fuel-film is not burnt perfectly in cylinder, it is exhausted in the form of HC emission. In this paper, three measurement techniques were utilized to measure spray characteristics and the amount of fuel-film in the cylinder. At first, PMAS was used to measure the spray characteristics such as size distributions, SMD, and spray angle. Secondly the amount and distribution of fuel-film which flow into through intake valve could be measured quantitatively using the fuel-film measuring device. And lastly, by optical fiber type spark plug used to detect the diffusion flame, the amount of unburned HC was measured. As the result of these experiments, the information of optimal spray characteristics and injection condition to minimize fuel-film could be built up.

• 한국분무공학회지
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• 제9권1호
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• pp.37-42
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• 2004

In a port fuel injection system of engine, a large part of fuel injected into an intake port adheres on its wall and inlet valve. Consequently, the wall impinging spray interaction might occur the generation of several harmful phenomena. There are uncontrollable mixture formation, an accidental backfire and unburned hydrocarbons. Therefore, it is important to analyze the fuel behavior during the spray-wall interaction. In this study, splash characteristics of impingement and reflecting or scattering behavior of droplets of fuel injected from EFI nozzle were studied experimentally. A test fuel used is LAWS and its physical characteristics are similar to the conventional gasoline except for the ignition point. Since the liquid film formed immediately after impinging on an impingement plate is unstable, it is easy to cause secondary disintegration. In addition, when the intermittently impingement on the impingement plate with LAWS, the splash ratio is around 0.6. If an injection period becomes longer, liquid film will become thick and the splash ratio will fall bout 10 percent. On the other hand, when the injection period of an intermittent spray is long, the same time lapse as a continuous spray is shown.

• 한국지능시스템학회논문지
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• 제10권4호
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• pp.357-367
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• 2000

본 논문은 조속기의 밸브 위치의 제한을 고려한 불확실 비선형 전력 시스템의 부파수 제어를 위한 강인 디지털 퍼지 제어기의 설계기법을 제시한다. TSK 퍼지 모델을 이용하여 비선형 전력 시스템을 모델링한다. 리아푸노프 안정도 해석 이론에 기반하여 파라미터 불확실성을 포함한 비선형 전력 시스템의 TSK 퍼지 모델을 위한 강인 안정 조겅을 유도한다. 유도된 강인 안정 조건은 선형 행렬 부등식의 형태로 나타난다. 또한 지는형 디지털 재설계 기법을 이용하여 연속 시간상에서 운용되는 전력 시스템을 위한 디지털 제어기를 설계한다. 컴퓨터 시뮬레이션을 통하여 본 논문에서 제안된 부하 주파수 제어기 설계 기법의 효용성을 보인다.

• 유공압시스템학회논문집
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• 제4권3호
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• pp.13-21
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• 2007

A forklift is a motive machine powered by LPG, diesel engine or electric motors. The internal combustion engine type forklift is equipped with automatic transmission to meet the required drive load as well as the easy operation of the vehicle. This paper deals with the shift control and endurance test controller which is developed for the functional test of the newly designed automatic transmission on a dynamometer test bench. Its major function is to control the proportional solenoid currents, which is directly related to clutch pressures, for the given reference current trajectory during shift and sequential operation of shift schedule designed for the durability test at each gear. It also has the ability to monitor all the necessary test data through RS232 communication and log them to disk files. The current controller of embedded system is designed from the identified dynamics of solenoid coil and the current reference can be easily modified with a user interface software on PC so as to match the shift data by experiments.

• Journal of Korean Society for Atmospheric Environment
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• 제18권E4호
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• pp.181-190
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• 2002

A novel portable device for the direct measurement of alveolar breath carbon monoxide (CO) was developed. The major components of the device include a mouthpiece, non-rebreathing two-way valve, Teflon tube, and CO dosimeter. An alveolar CO measurement can be completed within 1.5 min when using the proposed device and measurement protocol. Measurements could be read to the nearest 0.1 ppm. Humidity did not influence the CO measurements taken by the CO dosimeter, plus there were no problems associated with the recovery and carryover of CO through the device. The criterion for significance in statistical analyses was p< 0.05. The average recovery was 103 and 99% for recovery and carryover experiments, respectively. Test results using the proposed alveolar CO measurement system reflected a good reproducibility. This reproducibility was also supported by the finding that the relative standard deviations (RSDs) of the data sets were less than 7％ for the loss experiment and less than 8% for the carryover experiment. Consequently, it would appear that the proposed device can be effectively applied to measure CO levels found in breath, thereby overcoming several disadvantages associated with the conventional bag and adsorbent tube sampling methods.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.111-112
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• 2006

A new MR cylinder with built-in valves using Magneto - Rheological fluid (MR valve) is proposed for fluid power control systems. The MR fluid is a newly developed functional fluid whose obvious viscosity is controlled by the applied magnetic field intensity. This MR cylinder, which is composed of cylinder with small clearance and piston with electromagnet, has the characteristics of simple, compact and reliable structure. This paper presents a method to control the pressure of MR cylinder by using Generalized Predictive Control (GPC) algorithm. The differential pressure is controlled by applying magnetic field intensity to MR fluid. The use of GPC controller is to generate a control sequence by minimizing a cost function in such a way that the future system output is driven close to reference over finite prediction horizons. Experimental results from real time control using GPC method compared with conventional PID control method are also shown in this paper.