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여지환(J.H.Yae),김태기(T.K.Kim),서명원(M.W.Suh),석창성(C.S.Seok),이재천(J.C.Lee),김성봉(S.B.Kim),이선일(S.I.Lee),김장성(J.S.Kim) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_2
Vehicle dynamic analysis have been widely investigated in the last ten years. This paper presents a mathematical vehicle model. braking force control parameters, wheel control logic, and vehicle control strategy to analyze the dynamic characteristics of a vehicle equipped with ABS(Anti-lock Brake System). Analyses on the braking characteristics were performed for straight and J-turn brakng on the various road surfaces including split-μ. Analysis results showed the combination of slip ratio and wheel acceleration were desirable for the control logic. The adoption of the wheel acceleration was necessary to decide the type of road surface. For the vehicle control strategy for split-μ. select high-low method was confirmed as the most effective one.<br/>
이재천(J. C. Lee),고재욱(J. U. Koh),권태황(T. H. Kwon),신행봉(H. B. Shin),손정훈(J. H. Son) 유공압건설기계학회 2010 유공압건설기계학회 학술대회논문집 Vol.2010 No.10
This research aims at static characteristics control of a proportional electronic control valve with the configuration of RCP system using a digital amplifier·controller. The goal of the study is to reduce hysteresis through configuration of a digital closed-feedback system from the existing analog open-system, and to compact the digital amplifier·controller. 8-bit for development is selected for controlling a proportional valve and the related circuit is designed. The designed amplifier is combined with valve, hydraulic oil pump, and PC to configurate RCP system. The PID controller is used for control algorithm within MCU. Especially, the problem of unstable flow-output, which is found during the static characteristics control test, is solved by tuning duty ratio of PWM. Finally, the amplifier, which is developed by our research team, is used to test and compare the valves produced by the two companies, Rexroth and SG Sevo, and to get the results of the two companies" static characteristics control performance test.
이재천(J.C.Lee),서명원(M.W.Suh) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.6_1
This article reports the development and application trends of energy regenerative braking systems into passenger vehicles. The components of ERBS, the capacity of energy storage units, and the operational strategy are examined for the effective design achieving the objectives of hybrid vehicle. Three classes of hydraulic hybrid ERBS-the pure hydrostatic, the hydro-mechanical, and the power assist-are introduced.<br/>
이재천(J.C.Lee) 한국자동차공학회 1997 한국자동차공학회 춘 추계 학술대회 논문집 Vol.1997 No.11_2
The dynamics of a hydraulic acoustic attenuator is so highly nonlinear and of high order that the modeling for time domain analysis is hardly obtained. In this paper, a state-space representation of a hydraulic acoustic attenuator utilizing electrical analogy is presented first, and the time domain response analysis is performed. The state-space model developed was validated by comparing the simulation results with the experimental results.
이재천(J. C. Lee),류하오(H. Liu) 유공압건설기계학회 2011 드라이브·컨트롤 Vol.8 No.2
The analysis of an air spring characteristics is necessary to design and control automotive air suspension system properly. A mathematical model of an air spring was derived in light of energy conservation first. Then static and dynamic experiments of the air spring have been fulfilled. The static stiffness with various initial pressures and effective areas were obtained from the static experimental results. Theoretical static stiffness obtained by using the mathematical model and effective area data is in close accordance with the experimental estimation. The dynamic experimental results show that the hysteresis in displacement-force cycle decreases when the frequency of the harmonic displacement excitation signal increases, but it does not change too much as the frequency is higher than 1Hz. And the dynamic stiffness goes up with increasing of the initial pressure and the excitation frequency.
롤 에너지 다이어그램을 이용한 롤오버 저감에 관한 연구
이재천(J. C. Lee),류하오(Hao Liu),윤권수(G. S. Yun),김현찬(H. C. Kim) 유공압건설기계학회 2014 유공압건설기계학회 학술대회논문집 Vol.2014 No.9
The rollover accident of vehicle is fatal. so it is necessary to avoid rollover for a vehicle. In this paper, the vehicle roll motion mitigate by using energy diagram. This paper focuses on how to determine the rollover stiffness threshold in a RSC system. In the paper, the equilibrium states of vehicle’s roll motion are analyzed firstly, and then the roll energy diagram is plotted to show how roll energy varies with the lateral acceleration. Thus, the rollover stiffness threshold is determined. The required minimal torque for the motor in the RSC system is calculated.
이재천(J. C. Lee),오상흔(S. H. Oh) 유공압건설기계학회 2009 드라이브·컨트롤 Vol.6 No.1
This study presents an analytical model of an automotive steeling hose containing tuner(flexible spiral metal tube) to reduce the ripple pressure induced by steering vane pump. The double-wall side branch composed in a steering hose containing tuner was analogically considered as a filter in a conduit. Specialized test equipment was manufactured for the estimation of speed of sound in a conduit and measurement of amplitude ratio between the propagated ripple pressures of inlet and outlet of the steering hose. Experimental data of entire frequency ranges can be obtained through the test once in short time. The results of three points’ measurement method and cross-correlation method to estimate the speeds of sound in a hose, tuner, and side branch respectively reveal that cross-correlation method can be used practically. The results of simulation and experiment were so close, especially in the range of engine idling speed, that the proposed analytical model in this study was validated. Sensitivity analyses and experiments show that longer tuner is preferable, and that the positive-positive composition of the steering hoses containing tuner is superior to others to attenuate ripple pressure.
클러치 마스터실린더 컵-시일 고무의 마찰계수 실험 연구
이재천(J.-C. Lee),임문혁(M.-H. Im),차종조(C.-J. Cha),허만대(M.-D. Hur) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
The friction coefficient of the rubber for clutch master cylinder were experimentally measured in this study. The cylinderical rubber samples for primary cup-seal and secondary cup-seal were tested against the aluminum or the steel plates of master cylinder housing under the various conditions of brake oil temperatures and normal loads. Dry sliding friction coefficients were also measured under various load conditions.<br/> The test revealed following results. First, the friction coefficient under fluid lubrication condition in general decreases, as the oil temperature or normal load increases. Second, the steel plate of low surface roughness yielded comparatively low friction coefficient on the range of 0.30~0.67 while the aluminum plate of high surface roughness yielded high friction coefficient on the range of 0.31 ~1.15. Third, the friction coefficient of dry surface contact decreases as the normal load increases contrary to the general principle of friction coefficient between metal plates.<br/>