• 한국공작기계학회논문집
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• 제13권1호
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• pp.100-106
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• 2004

All vehicles need the good quality of riding. Especially shifting shock is very important in the evaluation of the riding. Shifting shock is caused by transmission operation that one part and other part of gem are contacting together. This shock affect the feeling of driving. It is clear from these results that the shifting shock is affected by clutch pressure, pressure mode, inertia etc.

• 한국산업융합학회 논문집
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• 제4권3호
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• pp.305-310
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• 2001

Hydraulic power shifting systems of hydraulic travel motor may be far safer than mechanical power transmission systems. Thus, hydraulic power shifting systems are widely used for speed control on the hydraulic equipments. In the case of liquid shifting lines, the rapid change of area, such as valve closing, can result in a large pressure transient. It is necessary to assure proper control method in order to obtain the smallest shift shock. This study conducts the shock characteristics of hydraulic power shifting system of the hydraulic travel motor. Experimental results show that shock pressure depends on the operating pressure, flow rate and pipe line area. The shock characteristics can be applied for reducing shocks.

• 한국자동차공학회논문집
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• 제5권6호
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• pp.202-214
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• 1997

In automotive industries, one of major issues is the shifting shock, which is brought out when two clutches are engaged in an automatic transmission. The engagement and disengagement if two clutches means the variation of the D.O.F(degree of freedom) of system. Therefore to analyze the shifting performance, the variation of D.O.F should be considered in detail. Generally, the programs for analyzing the shifting transients have been developed as the problem-dependent codes because the artificial maris were usually used to indicate the change of shifting phase. To develop a software applicable to a general mechanism of transmissions, a self-determining algorithm of D.O.F must be applied. Through the experiences for the last several years, a generalized analysis software of shifting mechanism(so called by POTAS-MSM Version 2.0) has been developed. In this study, some major ideas of the software and the concept for the analysis of shifting characteristics are presented. In addition to that, this paper shows how to self -determine D.O.F of he multi-slipping systems using the stick-slip criterion on a single slipping mechanism. By using this software, the shifting characteristics of a vehicle are analyzed and compared with the experimental results.

• 드라이브 ㆍ 컨트롤
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• 제15권3호
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• pp.36-42
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• 2018

Agricultural tractors require frequent shifting to improve operation efficiency, and PST (Powershift Transmission) is considered as a suitable transmission. However, due to the inherent characteristics of the PST, shocks arise during shifting, which imparts a negative effect on the operator. Therefore, in order to improve the transmission performance of the tractor PST, researches on various methods including the hydraulic system circuit, the engine input speed control, and the mechanical system of the transmission are steadily being conducted. In this study, in order to reduce the impact of PST on a shift based on SimulationX software, we analyzed the characteristics of the input signal of PCV (Pressure Control Valve) through sensitivity analysis and verified the simulation model through actual vehicle test. Optimization was performed for minimizing the shift shock for some of the parameters of the input signal at constant temperature and RPM conditions.

• International Journal of Automotive Technology
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• 제7권2호
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• pp.155-160
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• 2006

This paper presents a vehicle model for analyzing the transient shifting characterisitics of a passenger car with automatic transmission. Then the presented vehicle model was linked with the dynamic model of an automatic transmission. In order to identify the parameters of the vehicle model, we installed a test equipment with an accelerometer in a conventional vehicle and performed road tests. With the proposed vehicle model, we simulated the dynamic characteristics during shifting, and benchmarked with experimental results. Moreover, a modal analysis was carried out to investigate the effect of the vehicle model in the frequency domain and to obtain the transfer function of the vehicle model. In addition, we showed the numerical results in the time domain for analyzing the effect of each stiffness element, such as engine mountings and suspensions.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1996년도 춘계학술대회 논문집
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• pp.67-71
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• 1996

The dynamic equation is built by the mathematical modelling. The modelling is composed of various components used for the automatic transmission of tracked vehicles. When the transmission is shifting, the shock occurs in the drivetrain. The transient torques affect the durability and reliability of the vehicle. The factor and design point are analyzed for the transmission.

• 한국추진공학회지
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• 제25권3호
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• pp.1-13
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• 2021

추력이 최적화된 노즐의 초음속 유동장에 대한 노즐벽면각도의 영향이 수치해석적으로 조사되었다. 30톤급 로켓엔진의 연소기와 작동조건이 최적노즐형상을 조사하기 위하여 선택되었다. 연소생성물의 노즐유동은 케로신-액체산소의 이동평형계산에 의해서 구현되었다. 노즐벽면 각도의 변화는 내부충격파 및 2차 충격파의 발달형태를 다르게 유도하였다. 내부충격파가 노즐출구에서 특정위치에 있을 때 최적노즐이 얻어졌다. 최적노즐에 대한 노즐벽면 각도들은 충격파를 고려하지 않고 얻어진 최적노즐 형상과 매우 유사하게 얻어졌다.

• 제어로봇시스템학회논문지
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• 제14권3호
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• pp.301-306
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• 2008

Drivers are becoming more fatigued and uncomfortable with increase in traffic density, and this condition can lead to slower reaction time. Consequently, they may face the danger of traffic accidents due to their inability to cope with frequent gear shifting. To reduce this risk, some drivers prefer automatic transmission (AT) over manual transmission (MT). The AT offers more superior drivability and less shifting shock than the MT; therefore, the AT market share has been increasing. The AT is controlled by an electronic control unit (ECU), which provides better shifting performance. The transmission control unit (TCU) is a higher-value-added product, so the companies that have advanced technologies end to evade technology transfer. With more cars gradually using the ECU, the TCU is expected to be faster and more efficient for organic communication and arithmetic processing between the control systems than the l6-bit controller. In this paper, the model of an automatic transmission vehicle using MATLAB/Simulink is developed for the Hardware in-the-Loop (HIL) simulation with a 32-bit embedded system, and also the AT control logic for shifting is developed by using MATLAB/Simulink. The developed AT control logic, transformed automatically by real time workshop toolbox, is loaded to a 32-bit embedded system platform based on Freescale's MPC565. With both vehicle model and 32-bit embedded system platform, we make the HIL simulation system and HIL simulation of AT based on real time operating system (RTOS) is performed. According to the simulation results, the developed HIL simulator will be used for the performance test of embedded system for AT with low cost and effort.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권4호
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• pp.331-342
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• 2011

The transmission of tracked vehicles performs complex functions as steering, shifting, braking, etc. and the system level life time has been a key influenced by the number of sub-parts like as gear assembly, torque converter, clutches, bearings and so on. In particular, the mechanical type steering system in tracked vehicle has impact shock torques in steering shift and those kind of shock torques can effect on the durability of many sub-parts in power train system. The field failure modes of gear assembly, steering assembly and the bearings of output shaft appear as a very complex phenomenon. In this study, the actual failure, which may occur in field, of the transmission was investigated comprehensively and that the endurance test on the resulting output shaft bearing failure analysis and life assessment was performed. Life time test method used in this study, developed for the purpose of the internal usage, and under these testing techniques the impact of the each bearing damage, which used in tracked vehicle transmission left / right outputs of different structures, was analyzed.

• 대한기계학회논문집B
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• 제26권11호
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• pp.1488-1495
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• 2002

The response time represents how fast a system responds to a given disturbance at the system boundary. Flow restricting devices for controlling transients can result in a decrease in the peakm pressure, but may change response time. Response lag in a hydraulic system leads to inefficient working cycle and operator discomfort. The experiments were conducted in order to get information on the parameters which exert appreciable influence on the response time. The experimental apparatu including a hydraulic actuator, orifice and a hydraulic pump was an idealization of a bucket hydraulic shifting system. Experimental results show that the response time depends on operating pressure and flow rate. The effects of orifice type and size on the response time are quantified.