• 한국정밀공학회지
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• 제22권8호
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• pp.108-117
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• 2005

In modern industrial society, many kinds of valves have been used to control fluid flow. For the optimization of a ball valve, a quarter of spherical ball was modeled and evaluated. However, there is a difficulty in the application of the optimization technique because of the complexity of the fluid and the restriction of analysis. Therefore, in this study, it is performed to evaluate the stability of an initial model using FEM(Finite Element Method) and CFD. In addition, a shape optimization design of the valve is accomplished using an orthogonal arrangement and characteristic functions. From the result, a new design method is represented that could overcome the time and space restriction in structural design, such as the divided ball valve with less experiment.

• 한국염색가공학회지
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• 제12권4호
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• pp.233-238
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• 2000

In this study, the control system of sodium hydroxide was demonstrated to systemize hydrolysis process in polyester dyeing. We mainly focused on the application method of acid-alkali titration for the polyester hydrolysis machine of liquor-flow type. Industrial pH meter with electrode type was used for identifying equivalence point. Three units which were analogue-to-digital card, microprocessor and digital output card were used to control NaOH concentration in the control part of the system. The yielded data are translated to the microprocessor through analogue-digital interfacing card. After calculating, NaOH concentration in NaOH storage tank was controlled through the digital output card and solenoid valves.

• 드라이브 ㆍ 컨트롤
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• 제12권1호
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• pp.9-14
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• 2015

In the early of 1950, the high response magnetic torque motor was developed for driving electro-hydraulic servo valves. Since then it has been broadly used for industrial application and the research of development or improvement of the torque motor is still being conducted. The purpose of this study is to present useful design criteria for the torque motor design. For this, torque motor is modelled and linearized. The static characteristics of the torque motor are investigated by direct computation of the derived linearlized equations. The dynamic characteristics of the torque motor are investigated with the derived transfer function by using Matlab and compared with the results of the linearlized analysis by using AMESim simulation with actual values of the physical parameters. Finally, the design criteria obtained from the analysis are reviewed.

• Journal of Advanced Marine Engineering and Technology
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• 제23권2호
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• pp.236-243
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• 1999

This study deals with the application of high speed on-off valves to an electro-hydraulic servo indexing system incorporated electro-hydraulic servo valces. Comparing with the electro-hydraulic servo valve the high speed on-off valve has some merits. Which included low price robustness to the oil contamination and dircect control without D/A converter. The considered sys-tem of this study is controlled by pulse width modulation(PWM) of the control law which is pro-duced by a PID controller which is used broadly in industrial equipments. The dynamic character-istics corresponding to variations of system parameters such as inertia moment system gain and supply pressure are investigated by computer simulation and experiment. Consequently the availability of the application of high speed on-off valve to servo indexing system instead of electro-hydraulic servo valve is confirmed.

• 드라이브 ㆍ 컨트롤
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• 제13권1호
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• pp.34-42
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• 2016

This study studied how the clearance, overlap and mismatch errors of spool-sleeve affect the static pressure characteristics of a servo valve. A computer simulation model was established as a direct acting servo valve and a series of simulations was conducted for various values of clearance, overlap and mismatch errors. Pressure gain decreased as the clearance increased. The overlap also affects the pressure gain and was similar to the effect of clearance. Asymmetry of the pressure plot got worse and worse as the mismatch error increased.

• 농업과학연구
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• 제47권1호
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• pp.43-58
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• 2020

Mulching plastic is used for the purpose of maintaining soil temperature, moisture, and weed and pest prevention in agriculture. Any remaining plastic after use may contaminate the soil and damage crop growth. To solve this problem, mulching plastic wrappers have been studied and developed, but the actual use rate is quite low due to their poor performance and frequent tearing of the plastic on the field. In this study, we developed a tractor attachable mulching plastic wrapper to minimize the tearing of the mulched plastic. The developed mulching plastic wrapper consists of hydraulic motors and pumps, valves, a microcontroller, and sensors. The collecting speed of the plastic mulch was calculated considering the tractor's travel speed and the radius of the collecting drum. A proportional controller was designed to control the rotating speed of the hydraulic motor as the plastic was wound around the collection drum and the radius increased. The performance of an indoor experiment was quite promising because the difference between the collecting speed predicted by the calculation and the actual collecting speed was 2.71 rpm. Based on a field verification test, the speed difference was max. 14.28 rpm; thus, the, proportional integral derivative (PID) controller needs to be considered to control the drum speed precisely. Another issue was found when the soil covered at the edge of the plastic was hardened or the road surface was uneven, the speed control was unstable, and the plastic was torn. In future research, vibrational plows will be equipped to break-up the harden soil for collecting the plastic smoothly.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.27-32
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions fur passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed. It is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper which offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-offbecomes smooth when the fixed orifice size increases. Damping forces are measured with the change of the solenoid current at the different piston velocities to confirm the maximum hysteresis of 20N, linearity, and variance of damping farce. The damping farce variance is wide and continuous, and is controlled by the spoof opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.

• 한국재료학회지
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• 제34권1호
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• pp.44-54
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• 2024

High-Manganese (Mn) austenitic steel, with over 24 wt% Mn content, offers outstanding mechanical properties in cryogenic settings, making it a potential replacement for existing cryogenic materials. This high manganese steel exhibits high strength, ductility, and wear resistance, making it promising for applications like LNG tanks, flanges, and valves. To operate in cryogenic environments, hot forging and heat treatment processes are vital, especially in flange production. The cooling rate during high-temperature cooling after hot forging plays a critical role in influencing the microstructure and mechanical properties of high manganese steel. The rate at which cooling occurs during this process influences the size of the grains and the distribution of manganese and consequently has an impact on mechanical properties. This study assessed the microstructure and mechanical properties based on different cooling rates during the hot forging of High-Mn steel flanges. Comparing air and water cooling after hot forging, followed by heat treatment, revealed notable differences in grain size. These differences directly impacted mechanical properties such as tensile strength, hardness, and Charpy impact property. Understanding these effects is crucial for optimizing the performance and reliability of High-Mn steel in cryogenic applications.

• 한국산학기술학회논문지
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• 제18권7호
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• pp.417-422
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• 2017

대량살상무기를 이용한 전쟁 발발 시 가장 위협적인 것은 일반적으로 눈에는 보이지 않으면서 극소량으로도 사망에 이를 수 있다는 것이다., 군 당국은 화생방 오염상황 발생 시 전투원의 생존성을 보장하기 위해 개인 및 화생방대피분야에 대해 상당한 노력을 투입하고 있다. 따라서 본 논문에서는 화생방 방호시설에 사용되는 각종 차단밸브의 제어에 이용되는 양압측정을 위한 모듈과 화학탐지 모듈을 개발하였다. 또한, 수작업에 의한 제조 공정으로 품질의 균일성이 부족하고, 불량품 과다 및 제조 원가가 높은 단점을 개선할 수 있는 고성능 가스차단밸브를 개발하였으며, 여기에 양압측정 및 화학탐지 모듈을 적용하여 화생방방호시설의 제어에 사용하였다. 개발된 가스차단밸브는 규정풍속에서의 압력손실 28[Pa] 및 내부압력 30[kPa]에서 기밀특성을 유지하였다. 원격에서 측정된 양압에 따라 가스차단밸브의 제어가 가능하므로 향후 수입대체 및 국방관련 기술의 대외 독립성 확보가 가능할 것으로 기대된다. 또한 재래식 무기 및 핵폭발에 의한 폭풍압의 급격한 유입으로 인한 피해를 예방하기 위하여 화생방 방호시설의 외부와 연결된 모든 흡기구나 배기구에 설치하여 시설내의 인명 및 장비 등을 보호할 수 있다.

• 한국기계가공학회지
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• 제10권6호
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• pp.50-55
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• 2011

The fluid power products are widely used in current industrial area such as automation of products and equipment assembly, high-tech machine tool, aircraft, train, and etc. As the development of industry is in progress, the development of the fluid power products is demanding and it is required in every industrial area. This research proposed a pneumatic system to evaluate displacement accuracy of the pneumatic actuator without external load and to analyze capability of integration of the valve system. The pneumatic system consisted of a combination of pneumatic actuator, four two-port valves, two three-port valves, two pressure valve, a check valve, two proximity sensors, and a program logic controller (PLC). The position controller is based on the PLC connected with the proximity sensors. The maximum air pressure applied for tests was $49.05N/cm^2$ and the displacement accuracy of a stroke was measured using a dial gauge. The supply- and discharge-side of air pressure and the length of the stroke of the pneumatic cylinder were varied The test of the position control of the pneumatic cylinder was carried out 50 times at each supply- and discharge-side air pressure of 24.53/34.34, 29.43/39.24, 34.34/44.15, and $39.24/49.05N/cm^2$ and replicated three times. The accuracy of the displacement of the pneumatic cylinder stroke increased as the supply- and discharge-side of air pressure increased with the stroke length of 133mm. Also the displacement accuracy increased as the stroke length increased with the fixed supply- and discharge-side of air pressure of the pneumatic cylinder as 34.34 and $44.15N/cm^2$, respectively. The most accurate displacement of the pneumatic cylinder was obtained at the supplyand discharge-side of air pressure of 39.24 and $49.05N/cm^2$, respectively, and strokes of 170 and 190mm.