• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.81-91
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• 2000

Dynamic models of line regulator valve(LRV) and ratio control valve (RCV) are obtained for an electronic controlled CVT. LRV and RCV are operated by variable force solenoid(VFS). Considering the CVT shift dynamics, oil pump's efficiency and saturation characteristics of VFS, simulations are performed and compared with test results. Simulation results are in good agreement with the experiments, which shows the validity of the dynamic models of LRV and RCV obtained. In addition, the effects of the orifice size in the exhaust port of RCV are investigated. Simulation results show that as the orifice size decreases, the residual pressure in the primary actuator increases which insures the large torque transmission capacity, meanwhile the duration time for the downshift increases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.674-679
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• 2002

As the object of this study, a transmission system with the style of HST in combination with mechanical semi-automatic transmission for application in hydraulic wheel excavators was chosen. The dynamic characteristics of the object transmission was studied by numerical analysis of the mathematical model. The results of numerical analysis showed comparatively good agreements with experimental results, so the validity of the numerical analysis process was ascertained.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.105-114
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• 2001

In this study, a shift control algorithm far improving the shift quality of a parallel hybrid drivetrain with an automated manual transmission (AM) is proposed. The general AMT requires the sophisticated control of clutch in the clutch engagement to improve its shift characteristics, and that is generally known to be difficult. But in this hybrid drivetrain, we can control the speeds of clutch plates by engine and motor control, and it provides the easier clutch control in shift process than general AMT. Additionally, it permits the much-reduced shift shock. The motor control during the shift period is also to achieve reduced velocity drop of the vehicle in comparison with that of a general AMT. Furthermore various dynamometer-based experiments are carried out to prove the validity of the proposed shift control algorithm.

• Journal of the Korean Institute of Gas
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• v.24 no.6
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• pp.55-60
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• 2020

As research and development of eco-friendly vehicles are expanding worldwide, additional devices of vehicles are reduced or deleted to increase the mileage, or research is being conducted to reduce weight. Among them, the multi-stage transmission that was applied to the internal combustion engine vehicle was deleted and replaced with a reducer, and the initial driving power is secured by increasing the torque through the control of the motor output value. However, since frequent motor speed change can result in a load increase, this study attempts to develop a compact and lightweight manual two-stage reducer with a general reducer structure. Therefore, a two-speed transmission with two gear ratio was designed by inserting a large gear and a small gear in a structure with a parallel shaft to connect the gears with a V-belt in the form of a parallel shaft reducer, and setting the gear ratio of the low and high gears respectively. In addition, power performance according to the rotational speed and load of the transmission was checked through a test, and the heat generation characteristics generated during driving were checked to verify the validity of the transmission.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1996.03a
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.654-662
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• 1998

Shift quality of an automatic transmission in a vehicle is mainly affected by transient pressures in the hydraulic system during shifting. In this study, dynamic modelings of the hydraulic system and the power train of an automatic transmission are made systematically by a bond-graph method. The dynamic characteristics of the line pressures and clutch/brake pressures during shiftings are investigated by simulations and verified by experiments. The effects of clutch/brake pressures on the shift torque are also investigated through driving simulation.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.5
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• pp.179-187
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• 2001

In this paper, a primary pressure regulating type ratio control system is developed for a metal belt CVT, and the CVT ratio changing characteristics are investigated by simulation and experiment. The hydraulic part of the ratio control system has a simple structure with one 3-way spool valve as a main ratio control valve and one bleed type variable force solenoid as a pilot valve. The mathematical modelling of the CVT hydraulic system is derived by considering the CVT shift dynamics. Simulation results of CVT speed ratio and the primary pressure agree with the experimental results demonstrating the validity of the dynamic models. It is found from the simulation and experimental results that the response time of speed ratio and primary pressure can be shortened by increasing the ratio control valve port area, and the size of feedback orifice of ratio control valve gives a damping effect on the primary pressure oscillation.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.3 s.180
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• pp.86-93
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• 2006

This study is concerned with the investigation of characteristics of an AMT (Automated Manual Transmission) which are composed of clutch part and transmission part. When a shilling signal is received from the controller, the clutch is disengaged first, and shifting action including selecting action is followed, and then the clutch is engaged last. The characteristics of transmission shifting response are affected by various parameters of clutch and transmission control elements. Analytical results are in fair agreement with experimental results. It is found that the operating pressure level is the most important for the response of AMT characteristics, and that the other parameters such as natural frequency and damping ratio of the control valve are less important.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.154-162
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• 2004

In this study, a mathematical model for analyzing the shifting transients of the passenger car with an automatic transmission is proposed. The proposed model comprises a power transmission system and a vehicle system, which are coupled. In order to extract the modeling parameters, on-road car test is carried out. The model is composed of a detailed powertrain, an engine/AT housing, a simplified suspension system, tires and a vehicle body model. On the test, the vehicle accelerations and pitch ratio are measured by using accelerometers and a gyro sensor. The speeds, the brake signal, and the throttle position are taken from sensors which already exist in the vehicle. Considering natural ftequencies, which is calculated from the measured accelerations, and the characteristic equation, vehicle model parameters are identified. Dynamic behaviors during upshift or downshift are simulated using the proposed vehicle model. By comparing and analyzing the simulation result and on-road car test data, the vibration of the Engine/AT housing influences the shifting transients. The effect of model parameters are also studied. Among model parameters, the location of engine mountings influences the vibration of the vehicle body.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.143-151
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• 2001

During the past several years, the major interests of car manufacturers in development of automatic transmission were in durability and shift quality. However, a large number of researches for improving shift quality that are based on dynamic characteristics of shifting mechanism have been rarely adopted in the developing process because it is quite difficult to predict the shifting performance from the dynamics simulation. One of the important reasons for the difference between simulation results and experiments arises from the automatic transmission hydraulic system that consists of many valves with high order model and shows a lot different dynamics to temperature variation. In this work, hardware-in-the-loop simulation system for automatic transmission was developed f3r improving the accuracy of simulated result by combining the real-time simulation model with the real hydraulic system. The real-time simulation for automatic transmission model excluding hydraulic system is executed with TI's TMS320C31 DSP and the interfacing board which includes 12bit A/D, PWM signal generator and driver, serial driver ,etc is designed for acquiring the simulation data and signal interface with hydraulic system. We verified the proper operation and correctness of shifting result by comparing the off-line simulation result with that of HILS and experimental result which was performed on transmission dynamometer driven by electric motor.