• 한국자동차공학회논문집
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• 제7권7호
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• pp.221-228
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• 1999

A full-time four wheel drive vehicle is driven literally full time by the front and the rear wheels. Front and rear drive shafts are rotated rapidly in the extremely torsional state, which can cause various vibration and noise problems. The purpose of this study is to reduce the vibration and the noise of the full -time four wheel drive vehicle. In this paper, both the causes and the methods for reduction of torsional vibration are suggested. For this study, the characteristics of the torsional vibration are analyzed by free and forced torsional vibration simulation. And this paper described the influence upon the torsional vibration with emphasis shafting system. The validity of simulation models is checked by the field test. The forced vibration simulation with the variations of shaft design factors are performed by the checked models. According to the simulation , the resonance region shifts and the torque fluctuation varies in the system,. Finally, the methods and the effects for the torsional vibration reduction in driveline are proposed.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.319-329
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• 2016

Globally, many researchers have been trying to improve the fuel economy of a vehicle for satisfying future $CO_2$ regulation and minimizing air pollution problem. For the same background, diesel engine and vehicle system optimization using simulation models have been key technologies for the improvement of vehicle system efficiency. Therefore, in this study, calibration method for the air breathing system of a WGT diesel engine using mean value model has been composed for efficient engine and vehicle optimization simulation researches. And virtual WGT performances have been calculated for a 2 cylinder downsized diesel engine system. From these researches, the calibration method for the boost pressure and EGR rate of a virtual diesel engine related with WGT performances could be composed and some of technical issue related with downsized diesel engine could be investigated.

• International Journal of Automotive Technology
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• 제2권4호
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• pp.157-164
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• 2001

The vehicle electric power system, which consists of two major components: a generator and a battery, which have to provide numerous electrical and electronic systems with enough electrical energy. A detailed understanding of the characteristics of the electric power system, electrical load demands, and the driving environment such as road, season, and vehicle weight is required when the capacities of the generator and the battery are to be determined for a vehicle. An easy-to-use and inexpensive simulation program may be needed to avoid the over/under design problem of the electric power system. A vehicle electric power simulator is developed in this study. The simulator can be utilized to determine the optimal capacities of generators and batteries. To improve the expandability and easy usage of the simulation program, the program is organized in modular structures, and is run on a PC. Empirical electrical models of various generators and batteries, and the structure of the simulation program are presented. For executing the vehicle electric power simulator, data of engine speed profile and electric loads of a vehicle are required, and these data are obtained from real driving conditions. In order to improve the accuracy of the simulator, numerous driving data of a vehicle are logged and analyzed.

• 한국자동차공학회논문집
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• 제25권1호
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• pp.103-110
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• 2017

Most commercial vehicles have adopted the hydraulic power steering system. To reduce fuel consumption and to improve steering controllability, a hybrid electric power steering system is being developed for commercial vehicles. In this study, the HILS (Hardware In the Loop Simulation) system equipped with a commercial vehicle hybrid electric power steering system was developed and the vehicle dynamic performance of a truck with the steering system was evaluated. The hybrid electric power steering system is composed of the EHPS motor pump, column mounted EPS system, and ball nut steering gear box for heavy commercial vehicles. The accuracy of vehicle models equipped with the HILS system was verified with comparisons between the simulation results and field test results. The road reaction forces of the steering system were generated from the vehicle model and verified using field test results. Step steering tests using the verified HILS system were carried out and the performance of a newly developed commercial vehicle hybrid electric power steering system was evaluated.

• International Journal of Automotive Technology
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• 제6권4호
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• pp.403-411
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• 2005

The bus is regarded as one of the most frequently used public transportation systems, the research and development on driving stability, safety, and convenience for drivers and passengers has tremendously increased in recent days. This paper investigated the design of the bus door mechanism composed of an actuator (or motor) and linkages. The bus door mechanism is divided into many types according to the coupling of the linkages and the driving system. The mathematical models of all types of door mechanism have been constructed for computer simulation. To design the bus door mechanism, we developed a simulation program, which automates the kinematic and dynamic analysis according to the input parameters of each linkage and the driving system. Using this program, we investigated the design parameters that affect the kinematic and dynamic characteristics of the bus door mechanism under various simulation conditions. In addition, simple examples are examined to validate the developed program.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.80-89
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• 1993

Performance simulation for a Spark Ignition Wankel rotary Engine is presented in this paper. The volume of chamber at each eccentric shaft angle is evaluated by using geometric models of housing and rotor. A thermodynamic model which includes the first law of thermodynamics, combustion and convective heat transfer from chamber contents to surroundings is imployed. A thermochemical equilibrium model which considers 10 species(CO, $CO_2$, $O_2$, $H_2$, $H_2O$, OH, O, NO, $N_2$) in the burned gas region, is also employed. Four processes of gas exchange, compression, combustion and expansion are considered and the pressure, temperature and composition of chamber gas at each eccentric shaft angle in each process are computed in this performance simulation. This performance simulation must be useful for optimal design of Spark Ignition Wankel Rotray Engine with parametric study for various design parameters and operating conditions.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.105-112
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• 2005

Analyses of dynamic models which were one and two degrees of freedom, and had the nonlinear springs and dampings with certain polynomial functions were performed from SIMULINK in MATLAB. Those consisted of 12 programs and were built on the basis of the preceding programs fur the linear dynamic simulations. However the programs for the nonlinear simulations were quite different from those f3r the linear ones, and showed the results of the analyses in real time with animating. It was found that the programs would help us to solve any kind of nonlinear dynamic simulation with one and two degrees of freedom. Especially, the simulations for 1 DOF system with cubic nonlinear spring farce showed the results for Duffing's equation, of which phenomena were jump-up and jump-down. It will be applied to the dynamic simulation of the car seat vibration with a passenger, of which model has the equivalent nonlinear springs and is two degrees of freedom.

• 한국자동차공학회논문집
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• 제5권5호
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• pp.73-85
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• 1997

An automatic transmission is an important element of automotive power systems that allows a driving convenience. Compared to a manual transmission, however, it has a few problems in efficiency, shift feel, and maintenance. To improve these, it is imperative to understand the dynamics of automatic transmissions. This paper develops a dynamically-correct model of an automatic transmission, using the bond graph method. The bond graph method is ideally suited for modeling power systems, because the method is based on generalized power variables. The bond graph method is capable of providing correct dynamic constraints and kinematic constraints, as well as the governing differential equations of motion. The bond graph method is applied to 1-4 in-gear ranges, as well as various upshifts and downshifts of an automatic transmission, which allows an accurate simulation of an automatic transmission. Conventional automatic transmission models have no dynamic constraint, which do not allow correct simulation studies.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.101-109
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• 2004

Three models with various degree-of-freedom for a manual transmission clutch full-size tester have been developed and the models' reliability and accuracy have been verified using the measured data. A simulation study has also been conducted to understand dynamic behavior of the tester. The model for this simulation study includes clutch disk friction and damper dynamics. The developed model is very accurate in terms of maximum torque exerted on the clutch, slip duration and the vibration response except a slight difference compared to the measured data. In a history graph of the clutch torque, the maximum torque response from simulation is flat but the measured is sunken with a noticeable curvature. This phenomenon is found to be irrelevant to the dynamics of the full-size tester but is originated from the characteristics of the clutch itself. Thus, the full-size tester has been proven to be a reliable tester for clutch's power and torque transmission capability. To obtain a better understanding of clutch's characteristics and relationship between full-size tester and other testing methodologies, future research directions have been suggested.

• 한국자동차공학회논문집
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• 제13권4호
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• pp.8-18
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• 2005

Pedestrians involved in traffic accidents manifest unique trajectory characteristics depending on the collision speed, vehicle configuration, and pedestrian postures. However, the existing analytical models for pedestrian movements do not fully include the rotational characteristics of the pedestrians because they assume a two dimensional parabolic trajectory. This faulty assumption in the development of these models limits their applicability and reliability This study investigated the pedestrians movement at collision by computer simulation. The simulations are carried out by using HADYMO, which is a special simulation software system for dynamic movement analysis. Vehicles and pedestrians are modeled and verified via real crash worthiness experiments. Simulations are performed for various collision speeds, vehicle configuration, and pedestrian postures. Since the simulation uses multi-body dynamics, It can express irregular phenomena of the bodies quite well. The results can be exploited for vehicle design and traffic accident reconstruction.