• 제어로봇시스템학회논문지
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• 제11권2호
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• pp.103-108
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• 2005

Loading/Unloading task in the real industry is performed by crane, but most of the loading/unloading task with the weight of 5kg∼30kg is done by human workers and this kind of work causes industrial disaster of workers. Therefore it is necessary to develop low cost loading/unloading manipulator system to prevent this kind of industrial accidents. This paper is concerned with the design and fabrication of 2 axis pneumatic manipulators using on/off solenoid valves and accurate position control without respect to the external load and low damping in the pneumatic rotary actuator. To overcome the change of external load, switching of control parameter using LVQNN (Learning Vector Quantization Neural Network) is newly applied, which estimates the external loads in the pneumatic cylinder. As an underlying controller, a state feedback controller using position, velocity and acceleration is applied to the switching control system. The effectiveness of the proposed control algorithms are demonstrated through experiments of pneumatic cylinder with various loads.

• 항공우주시스템공학회지
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• 제12권5호
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• pp.32-39
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• 2018

본 논문에서는 소형 압전유압펌프에 적용된 박판 스프링 형 체크밸브의 변형에 의한 이론적인 압력전달 비율을 계산하였다. 박판 체크밸브는 외력에 의해 변형이 발생하는 유연체이며, 체크밸브의 변형은 챔버 압력이 부하 압력으로 전달되는 비율에 영향을 미친다. 박판 체크밸브를 강체로 가정하였을 때와 유연체 모델일 때의 차이를 비교하기 위해 각각의 모델에 대한 이론적인 압력 전달 비율을 계산하였고, 유연체 체크밸브 모델의 압력 전달 비율 계산을 위해 P-delta 효과를 고려하였다. 또한, 유연체 체크밸브 모델의 변형을 고려하여 계산된 압력 전달 비율의 검증 실험을 수행하였다. 실험에는 박판 스프링 형의 체크밸브와 볼-박판 스프링 형의 체크밸브를 각각 적용하여 부하 압력을 측정하였다. 실험을 통해 얻어진 각각의 부하 압력을 이용하여 실험적인 압력 전달 비율을 계산하였다. 실험으로 얻어진 결과를 이론적으로 계산된 압력 전달 비율과 비교하여 P-delta 효과를 고려한 박판형 체크밸브 압력전달 해석의 타당성을 검증하였다.

• 한국자동차공학회논문집
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• 제11권6호
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• pp.21-29
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• 2003

Boosting of engine power by using Turbo- or Super-charger is a solution to comply with $CO_2$-regulation in Europe. Turbo-charger is now playing a major role in the field of charging system thank to its technical advantages such as no demand of operation power from engine. A mechanically driven Super-charger, however, is now popular due to quick speed response to change of the driving mode-high engine torque even at low engine speed. Since Super-charger needs operation power from engine, it is difficult to improve its relatively higher fuel consumption than that of Turbo-charger. This negative point is still an obstacle to the wide use of Super-charger. This study aims to develop power control concept to achieve the minimization of operation power when it is not necessary to charge at idling or part load driving condition. A screw type Super-charger was modified in design partially and adapted an internal bypass valve and a bypass tube to control charging pressure at part load. The various control concepts show a possibility to reduce operation power of Super-charger and result in improvement of fuel consumption.

• 항공우주기술
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• 제11권1호
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• pp.91-97
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• 2012

가스발생기 산화제 개폐 밸브에 사용되는 주름관의 구조 해석 및 시험이 수행되었다. 이 주름관은 극저온에서 압축 변위와 높은 외압 하중을 받는다. 구조 해석은 상온 및 극저온에서 EJMA (Expansion Joint Manufacturing Association) 표준 및 상용 유한 요소 해석프로그램인 Abaqus v6.9를 이용하여 수행되었다. 스프링 강성, 응력 및 피로 수명 해석 결과들이 비교되었고 유한 요소 해석 결과에서 접촉 및 재질의 소성에 의한 영향을 살펴보았다. 또한 파열 시험과 관련된 유한 요소 해석 결과도 제시되었다.

• 설비공학논문집
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• 제9권1호
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• pp.33-42
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• 1997

The reciprocating compressors are widely used in industrial fields for its simplicity in principle and high efficiency. But the design of it requires rigorous experiments due to its high dependence on many design parameters. In this work, a mathematical model is developed so that we can analyze the gas-solid interaction during the whole working processes of a reciprocating compressor. The governing equations, which represent the fluid-solid interaction, was derived from the unsteady Bernoulli's equation with the assumption of quasi-steady working process. The valve itself was assumed to be a one degree of freedom spring-mass-damper system. A simple thermodynamic relation, the ideal gas state equation, was used to give it an external force term assuming that the refrigerant behaves like an ideal gas. It was suggested to use a motor of higher driving frequency to enhance the performance of the reciprocating compressor without causing a faster failure of the valve.

• 한국정밀공학회지
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• 제21권3호
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• pp.100-108
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• 2004

Contamination of environment induces the shortage of drinkables. In this trend, the leakage of water that occurs by breakage or erosion of rubber valve seats is serious problem. Rubber is apt to cause breakage between two materials when they contact with each other. The possible way to avoid leakage of water by damage and breakdown of rubber is to replace that with metal. Because of this reason, nowadays, rubber is being substituted with metal as valve seat materials for water works. In tribology, a severe from of wear is characterized by local, macroscopic material transfer, removal, or formation of surface protrusions when two solid surfaces experience relative sliding under load. One of the major problems in sliding of metals is galling due to bad surface quality. Experimentally, there are various elements which influence on incipient galling, such as hardness, surface roughness, temperature, load, velocity and external environments. This paper is aimed at verifying the galling tendencies according to hardness, surface roughness, load and velocity and showing how much effect the factors have on the galling tendencies.

• 드라이브 ㆍ 컨트롤
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• 제13권2호
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• pp.26-33
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• 2016

This paper describes of a mathematical and real experimental analysis for a walking robot which uses servo valve driven hydraulic actuator. Recently, many researchers are developing a walking robot based on hydraulic systems for the difficult and dangerous missions such as walking in the rough terrain and carrying a heavy load. In order to design and control a walking robot, the characteristics of the hydraulic actuators in the joint through the view point of walking such as controllability and backdrivability must be analyzed. A general mathematical model was used for analysis and proceeds to position and pressure changes characteristic of the input and backdrivability experiment. The result shows the actuator is a velocity source, had a high impedance, the output stiffness is high in contact with the rigid external force. So stand above the controller and instruments that complement the design characteristics can be seen the need to apply a hydraulic actuator in walking robot.

• 한국산업융합학회 논문집
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• 제23권6_2호
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• pp.1007-1014
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• 2020

IMO(International Maritime Organization) continues to strengthen environmental regulations on exhaust gases such as CO2, NOx, SOx. As for sulfur oxides, from 1 January 2020, all ships on international voyages must use fuel with a sulfur content of 0.5% or less. Or, it is obligatory to use an exhaust gas treatment device that has the same effect. Shipping companies are using low-sulfur oil, replacing them with LNG fuel, or installing scrubbers that suppress sulfur oxide emissions. In the case of ships using bunker C oil, the load on the engine is lower when entering and departing, so the exhaust gas pressure is lowered and the scrubber cannot be properly utilized. Therefore, diesel oil with low sulfur content is used when entering and leaving the coast. When diesel oil is used, exhaust gas is directly discharged through the control system and piping system, and when bunker C oil is used, sulfur oxides are reduced by scrubbers through other control systems and piping systems to discharge exhaust gas. Accordingly, a company has developed a system called a three-way damper valve that can control exhaust gas emissions while integrating these two control systems and piping systems into one. In this study, the control characteristics of the integrated exhaust gas control system and structural safety against external loads in a high-temperature exhaust gas environment were reviewed.

• International Journal of Precision Engineering and Manufacturing
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• 제8권1호
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• pp.46-51
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• 2007

Environmental contamination creates shortages of potable water. In such situations, the leakage of water due to breakage or aging of rubber valve seats is a serious problem. Rubber is apt to break when it is placed between two materials that contact each other. One way to avoid water leakage due to rubber damage and breakdown is to replace the rubber with metal, which is currently taking place in water distribution systems. In tribology, a severe form of wear is characterized by local macroscopic material transfer or removal, or by problems with sliding protrusions when two solid surfaces experience relative sliding under load. One of the major problems when metal slides is the occurrence of galling. Experimentally, various conditions influence incipient galling, such as hardness, surface roughness, temperature, load, velocity, and the external environment. This study sought to verify the galling tendencies of metal according to its hardness, surface roughness, load, and sliding velocity, and determine the quantitative effect of each factor on the galling tendencies.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.626-631
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• 2007

MR(Magneto-rheological) fluid is smart material that can be changed viscosity by controlling the magnetic field. MR damper with MR fluid can control damping force. It can be used extensively many engineering structures for reducing the effect of dynamic external disturbances. There are three kinds of MR dampers, such as valve mode, direct-shear mode and squeeze mode. In this study, design process of direct-shear mode MR damper with the MR fluid gap was developed. The parameters that used in the direct-shear mode MR damper Informed from the experiment of valve mode MR damper of Lord company. Magnetic analysis with finite element method was performed to find the optimal annular gap.