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쇽업소버 이상 소음 개선을 위한 시스템 시뮬레이션 연구
김동명(D. M. Kim),윤영환(Y. H. Yoon),김도현(D. H. Kim),송경훈(K. H. Song),이용범(Y. B. Lee) 유공압건설기계학회 2019 유공압건설기계학회 학술대회논문집 Vol.2019 No.6
The abnormal noise produced by the vehicle’s shock absorber is a complex problem in the development of the vehicle. This study identifies the cause of chuckle noise among the abnormal noise of shock absorber and suggests a reduction method. Chuckle noise from shock absorber means the noise in the 200 to 800 ㎐ band which is produced inside the cabin by a road excitation of not more than 30 ㎐. To improve the abnormal noise of shock absorber, internal structural changes may affect ride quality, and thus cause difficulties in improvement. If the shock absorber model is constructed using CAE, the abnormal noise may be improved without repeated design changes. With an emphasis on structural induced noise, such as pistons, rods and valves that make up the shock absorber, the CAE analysis technique was used to identify the mechanism of abnormal noise by the shock absorber.
능동 현가 시스템용 비례압력제어밸브의 해석모델 개발 및 최적화 설계
김동명(D.M. Kim),장주섭(J.S. Jang) 유공압건설기계학회 2014 유공압건설기계학회 학술대회논문집 Vol.2014 No.4
Active suspension system is an important system for determining the driving stability and ride comfort of the vehicle. Active suspension system is composed of a cylinder unit power supply unit, and control valve unit. Control valve is a proportional pressure control valve, the dynamic characteristics of the valve affects the performance of the active suspension system. We have developed an analytical model, we analyzed the design of variable valve. Further, by knowing the variable impact on the system is high, and to optimize the design, and improved performance of the dynamic properties.
21톤급 전기 굴삭기용 파일럿 작동식 유량제어 밸브의 해석모델 개발 및 검증
김동명(D. M. Kim),남용윤(Y. Y. Nam),서자호(J. H. Seo),장주섭(J. S. Jang) 유공압건설기계학회 2015 드라이브·컨트롤 Vol.12 No.3
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.
김동명(D. M. Kim),노대경(D. K. Noh),장주섭(J. S. Jang),윤영환(Y. H. Yoon),김용주(Y. J. Kim),김수철(S. C. Kim) 유공압건설기계학회 2013 유공압건설기계학회 학술대회논문집 Vol.2013 No.10
The neutral valve as the controller of HST is one of important valves for the vehicle control. The neutral valve is the valve performing the role to transmit or block the power to the vehicle. The logical validity has been investigated by analyzing the serve circuit through the development of analytical model of neutral valve. The modelling used the simulationX as the commercial software. The analysis for the number of piston hole of Orifice Diameter, the size of pressure pulsation and the initial amount of compression have been performed in the sensitivity analysis of each design variable of this study.
김동명(D. M. Kim),이수용(S. Y. Lee),장주섭(J. S. Jang) 유공압건설기계학회 2013 유공압건설기계학회 학술대회논문집 Vol.2013 No.6
In this study, we try to develop hydraulic crane analysis model. The subject crane is gantry crane. Before producting system, we will simulate hydraulic circuit. In this way, it is considered to help us predict design specification validity and problem. The step of developing interpretation model is as in the following. The hydraulic parts are developed as unit model on the basis of catalogue. And sub circuit is constructed by extending unit model. We check the logic validity of sub circuit by analysing output from interpret model. It is considered to be basis of developing the whole crane models.
HST 중립밸브의 해석모델 개발 및 설계변수 민감도 분석
김동명(D. M. Kim),장주섭(J. S. Jang),김수철(S. C. Kim) 유공압건설기계학회 2014 드라이브·컨트롤 Vol.11 No.3
The neutral valve for controlling the HST is one of the important valves for the vehicle control. Neutral valve takes a role of blocking or transmitting power to the vehicle. The operating principle of the neutral valve was developed through the analysis model. We also investigated the logical validity by analyzing the results of the analysis model. The analysis model was developed by using SimulationX witch is commercial software. The number of holes in the piston was selected as a variable initial compression of the spring, and the magnitude of the pressure pulsations and the diameter of the orifice for the sensitivity analysis were performed to design sensitivity analysis of the neutral valve.
김동명(D. M. Kim),이정민(J. M. Lee),정원지(W. J. Jung),장주섭(J. S. Jang) 유공압건설기계학회 2015 드라이브·컨트롤 Vol.12 No.2
In order to control the actuators of hydraulic machinery such as excavators, various control valves are typically assembled in a single block. Such a control block is called a main control valve(MCV). In this paper, we analyzed the working principle and the particular purpose of the design of all valves included in the MCV system. To Examine the reliability of the analysis model, the pressure drop of the MCV at each port was measured. The authors developed an analytical model of the control valve(main spool, load poppet, pressure relief, make up, and regeneration). The authors considered the notch shape of the spool while developing the analytical models of the main spool valve. Most importantly, at the stage before the analysis model was applied in the design tuning, the reliability was ensured by comparing the analysis results with the test results. This paper showed a process of developing an analysis model that can be utilized in the design and tuning stages.
김동명(D. M. Kim),장주섭(J. S. Jang),김태인(T. I. Kim),이종찬(J. C. Lee),유충목(C. M. Yoo),한성민(S. M. Han),남용윤(Y. Y. Nam),서자호(J. H. Seo),박진선(J. S. Park) 유공압건설기계학회 2016 유공압건설기계학회 학술대회논문집 Vol.2016 No.6
Recently, an electronic hydraulic valves on behalf of the main control valve is widely used. The electric hydraulic valve is one of the main control valve to control the various actuators in the hydraulic system(This valve was a cartridge type of a 2port/2way and EHPV(Electro hydraulic proportional valve) and the main poppet is composed of a single valve. A main poppet in the electric hydraulic valve is determine to main flow line, which includes the ability to restrict or permit the reverse. Supply flow is proportionally controlled by the inner pilot pressure and the pilot pressure is controlled by the current of input EHPV. In general, pilot operated valves are supplied to the control pressure from the outside. However, this valve is supplied with pilot pressure from the inside. Therefore, the design variables of the main valve poppet and EHPV are closely related to each other. It was carefully analyzed the valve structure and how it works to improve the performance of the valve. We developed an analytical model considering the geometric shape and spring stiffness. The test results and the analysis confirmed the accuracy of the analysis model by comparing the results, and the performance enhancement study was performed using the analysis model. We examined the characteristics of the control range and the power loss by using the analysis model.
김동명(D. M. Kim),이정민(J. M. Lee),정원지(W. J. Jung),장주섭(J. S. Jang) 유공압건설기계학회 2015 유공압건설기계학회 학술대회논문집 Vol.2015 No.6
In this study, we develop analytical model of an open center system and the load-sensing system and analyze the system characteristics and efficiency. In order to analyze characteristics of the pressure and flow of the main control valve of an open center system, test was performed on a at each port. The authors studied the reliability of the analysis model by confirming the similarity of the analysis results and the test results before analyzing the characteristics of the system. Developing the main control valve of the load sensing type added a flow sharing valve and a notch shape to the open center system on the proven reliability. The authors was performed the simulation under the same load condition in order to compare the efficiency of the systems. Under the same load conditions, The authors was performed the simulation in order to compare the efficiency of the systems. Also, The authors was investigated in the combined operation performance by means of analyzing the characteristics of flow distribution under different load conditions.
디지털 무산동 영상의 변환을 이용한 망막신경섬유층 결손의 발견
한의석,박기호,김태우,김동명,Eui Seok Han,M,D,Ki Ho Park,M,D,Tae Woo Kim,M,D,Dong Myung Kim,M,D 대한안과학회 2006 대한안과학회지 Vol.47 No.5
Purpose: To evaluate the efficiency of digital retinal nerve fiber layer (RNFL) photographs converted from a non-mydriatic digital fundus camera for detecting RNFL defects. Methods: Ninety-five eyes were evaluated with both a non-mydriatic digital fundus photograph and a digital RNFL photograph by two glaucoma specialists independently. The red-free, monochrome modified digital fundus photograph was acquired from non-mydriatic digital fundus photographs using Photoshop 7.0. Whether a localized wedge-shaped or diffuse RNFL defect existed or not was evaluated on a non-mydriatic digital fundus photograph and a modified digital fundus photograph, and inter- and intraobserver agreement were also evaluated. Regarding the use of digital RNFL photographs as a standard method, we calculated the sensitivity, specificity, and positive and negative predictive values of the two types of photographs. Results: Interobserver agreement (Cohen`s kappa values) about localized RNFL defects observable on digital RNFL photographs, non-mydriatic digital fundus photographs, and modified digital fundus photographs were 0.749, 0.634, and 0.793, respectively, but all were 0.417 or less with regard to diffuse RNFL defects. Regarding localized RNFL defects, the sensitivity, specificity, and positive and negative predictive values of modified digital fundus photographs were 85.7%, 95.5%, 85.7% and 94.1%, respectively, showing superiority to those of non-mydriatic digital fundus photographs. But, in cases of diffuse RNFL defect, the sensitivity and specificity of modified digital fundus photographs were 60.0% and 97.8%, respectively, indicating no superiority to non-mydriatic digital fundus photographs. Conclusions: The localized RNFL defect can be detected more efficiently with modified digital fundus photographs than non-mydriatic digital fundus photographs, but the diffuse RNFL defect cannot.