• Journal of Drive and Control
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• v.12 no.3
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• pp.52-59
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• 2015

An electro hydraulic poppet valve (EHPV) and a variable orifice poppet are assembled in a single block, which is referred to as a RHINO but is also generally called a pilot-operated flow control valve. In this study, we analyzed the structure and the operating principle for a RHINO applied in a 21-ton electric excavator system. The RHINO was experimentally tested to measure the dynamic responses and the pressure energy loss. In this test, we investigated the variation in the conductance coefficient according to the increase in the supply pressure under a constant current and a variation in the flow rate according to the increase in the current. Then, the geometrical shapes and the spring stiffness of the RHINO were considered to develop an analysis model. The characteristics (current-force and hysteresis) for the solenoid based on the experimental data were reflected in the analysis model that was developed, and the reliability of the analysis model was also verified by comparing the experimental and analytical results. The developed model is thus considered to be reliable for use in a wide range of applications, including optimum design, sensitivity analysis, parameter tuning, etc.

• Korean Journal of Materials Research
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• v.8 no.1
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• pp.64-70
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• 1998

자동차의 엔진밸브 스프링으로 사용되는 Si-Cr 스프링강의 영구 변형 저항성과 내피로성이 우수한 고강도강을 개발하기 위하여 탄소함량을 증대시키고 Mo, V, W와 같은 합금원소를 기존의 SAE 9254 스프링강에 첨가하여 개발강을 제조했다. SEM및 EDX가 부착된 TEM을 이용하여 미세조직을 관찰했고, 크립시험 및 피로시험기를 이용하여 스프림의 영구 변형 저항성 및 스프링의 내피로성을 조사했다. 실험결과, 개발강은 피로 특성치는 기존강과 동등 수준이면서 인장강도가 기존강의 것보다 10%가 더높은 2100MPa 급의 고강도를 나타내었으며 또한 영구 변형 저항성도 현저하게 개선되었는데 이는 W, Mo의 첨가로 인해 템퍼링시에 세멘타이트의 성장이 억제되어서 세멘타이트의 석출물이 미세하게 되었기 때문이다.

• Journal of Species Research
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• v.9 no.2
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• pp.122-130
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• 2020

Cavernocypris reddelli n. sp. is a new species of the genus Cavernocypris collected from spring waters of Texas, U.S.A.. This is the sixth species of the genus described so far. It can be distinguished from the other species of the genus by the shape and length of carapace, presence of robust marginal pore canals on right valve, number and length of setae on second antenna, shape of hemipenis, numbers of whorls on the Zenker organ, and differences in other parts of chaetotaxy. The new species was compared with other species and a new taxonomic key for the genus is presented for future studies.

• International Journal of Fluid Machinery and Systems
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• v.4 no.4
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• pp.367-374
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• 2011

Water hammer pumps can effectively use the water hammer phenomenon in long-distance pipeline networks that include pumps and allow fluid transport without drive sources, such as electric motors. The results of experiments that examined the effect of the geometric form of water hammer pumps by considering their major dimensions have been reported. In addition, a paper has also been published analyzing the water hammer phenomenon numerically by using the characteristic curve method for comparison with experimental results. However, these conventional studies have not fully evaluated the pump performance in terms of pump head and flow rate, common measures indicating the performance of pumps. Therefore, as a first stage for the understanding of water hammer pump performance in comparison with the characteristics of typical turbo pumps, the previous paper experimentally examined how the hydrodynamic characteristics were affected by the inner diameter ratio of the drive and lifting pipes, the form of the air chamber, and the angle of the drive pipe. To understand the behavior of the components attached to the valve chamber and the air chamber that affects the performance of water hammer pumps, the previous study also determined the relationship between the water hammer pump performance and temporal changes in valve chamber and air chamber pressures according to the air chamber capacity. For the geometry of components attached to the drain valve, which is another major component of water hammer pumps, this study experimentally examines how the water hammer pump performance is affected by the length of the spring and the angle of the drain pipe.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.2
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• pp.214-222
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• 2017

Maritime deck machinery relies heavily on the importation of components produced by overseas companies. Our research defines design parameters for hydraulic winch regulators used in maritime deck machinery. Using Amesim, we were able to conduct 1D modeling, and utilizing CFS then enabled us to create 3D models. These models were analyzed in our research for changes in pressure on each port that resulted from the regulator's spring constant and changes in the primary tension-compression field. Our research then analyzed alterations in traits caused by changes in the length of overlap between the spool and sleeve. Last but not least, our research analyzed the trait alteration resulting from changing the interval between the spool and sleeve. We believe the results of our research can be used to design a hydraulic winch regulator used in maritime deck machinery that does not require importation.

• Journal of Biosystems Engineering
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• v.40 no.2
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• pp.95-101
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• 2015

Purpose: During the start-up period, the response time of a hydraulic system increases in the winter because of the increased oil viscosity caused by the cold weather. The problems of delayed tractor starting and excessive wear of the clutch disk occur for these reasons. Therefore, this study develops an analysis model using the commercial hydraulic analysis program AMESim to examine the characteristics of delays in power shuttle starting at different oil temperatures. Methods: In the experiment, a tractor was stationary on a flat surface with the engine running at a constant speed of 1,080 rpm. The forward lever was then pressed to activate the power shuttle at three different oil temperatures, and the pressure changes were measured. The pressure on the forward clutch control valve was measured by a pressure gauge installed on the hydraulic line supplied to the transmission from the main valve. An analysis model was also developed and verified with actual tests. Results: The trend of the simulated pressures of the power shuttle is similar to that of the measured pressures, and a constant modulation period was observed in both the simulation and test results. However, the difference found between the simulation and test results was the initial pressure required to overcome the initial force of the clutch spring. Conclusions: This study also examines the characteristics of the delayed startup of the power shuttle at different oil temperatures through simulations.

• The Korean Journal of Malacology
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• v.31 no.1
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• pp.43-48
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• 2015

Oxygen isotope ratios (${\delta}^{18}O$) of three Pacific oyster (Crassostrea gigas) specimens from the Neolithic Yeondae-do shell midden site, Tongyeong, Korea, were analyzed to determine the seasonality of shellfish gathering and site occupation. Oxygen isotope samples were taken from the left valve hinge sections of the specimens. Oxygen isotope values ranged between -0.1 ‰ and -2.4 ‰, between -0.2 ‰ and -2.9 ‰, and between 0.3 ‰ and -2.8 ‰ in oyster specimen #one, #two and #three, respectively. The isotope profiles showed seasonal temperature cycles, providing information related to the seasonality of shellfish gathering and site occupation. Hinge-edge oxygen isotope values of the specimens showed decreasing trends after passing through maximum values (winter), indicating that they formed during spring. Thus it can be assumed that during spring season, oysters were gathered and the site was occupied.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.10
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• pp.102-109
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• 2017

The high pressure pump of a diesel injection system compresses the fuel supplied at low pressure into high pressure fuel and maintains the fuel of the common rail at the required pressure level according to the engine operating conditions. The high pressure pump is required to operate normally in order to compress the fuel to a high pressure of 2000 bar during the entire lifetime of the vehicle. Consequently, a suitable design technique, material durability and high precision machining are required. In this study, the high pressure pump simulation model of a 1-plunger radial piston pump is modelled by using the AMESim code. The main simulation parameters are the displacement, flow rate and pressure characteristics of the inlet and outlet valves, cam torque characteristics, and operating characteristics of the fuel metering valve and overflow valve. In addition, the operating characteristics of the pump are simulated according to the parameter changes of the hole diameter and the spring initial force of the inlet valve. The simulation results show that the operation of the developed pump model is logically valid. This paper also proposes a simulation model that can be used for current pump design changes and new pump designs.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.208-211
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• 1993

This paper presents the parameter design method for the desired time response of hydraulic track motor system of an industrial excavator. The dynamic response depends upon many component parameters such as motor displacement, spring constant and various valve coefficients. Most of them are to be determined to obtain the desired response while some parameters are fixed, or discrete for the off-the-shelf type components. The parameters might be selected through repeated simulations of the system once the system is mathematically represented. This paper, however, presents optimization technique to select two parameters using a parameter optimization technique. The variational approach is applied to the system equations which are represented as state equations and from those system equations derived are the adjoint equations. The gradients for each parameter also are formed for the iterations.

• Journal of Advanced Marine Engineering and Technology
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• v.17 no.1
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• pp.26-32
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• 1993

The loads exerted on electro-hydraulic servo system are classified into inertial, viscous, and spring load. The additional load called disturbances is also exerted on system but is generally not modeled. To deal with these kinds of loads, it is necessary to maintain the continuous signal transfer, so we can construct compensator to satisfy control specifications using feedback signal such as displacement, velocity, acceleration and pressure known as state variables. In case of controlling the speed of hydraulic motor, we must keep up robust performance for the various loads and disturbances acted on the system. However, the load flow rate in the valve is characterized by nonlinearity so that traditional theory of linear control could not be expected to give the desired performance. In this paper, it is shown that speed controller of hydraulic motor gives a good command following and disturbance rejection performance by applying sliding mode theory as a way of robust control to the nonlinearity, variation of loads and disturbances.