• 한국자동차공학회논문집
• /
• 제18권6호
• /
• pp.138-144
• /
• 2010

If the vibration is occurred in a large-sized bus roof, it makes people annoying and complaining the quality of a large-sized bus. So in design stage, it must be considered. To assess vibration at the roof which is equipped with air conditioner in design stage, finite element model is constructed. Computer simulation analysis and experimental method are performed. The dynamic characteristics of the large-sized bus are found by using eigenvalue method. It is related with dynamic behavior. The running conditions of a large-sized bus are velocity and road condition which followed experimental conditions. And the frequency response of a large-sized bus is well correlated with analysis result. Modal participation method is used for finding major modes at each peak. Using this method, we found that front and rear suspension system, engine mounting system and roof structure are the major reasons of the roof vibration. To reduce vibration level of roof in a large-sized bus, spring stiffness of front and rear suspension system, spring stiffness of engine mounting system and roof structure are properly combined. From this study, the vibration characteristics of the roof structure of a large-sized bus can be to a satisfactory level.

• 한국자동차공학회논문집
• /
• 제5권6호
• /
• pp.148-154
• /
• 1997

The safety problems of buses have been arisen due to the increasing of road traffic. Occupant injuries are always possible in the rollover accident and the frontal impact. Thus the structure of bus should have sufficient strength to protect passengers under accidental loads. ECE(Economic Commission for Europe) regulation No.66 prescribes that the superstructure of the vehicle shall be sufficient strength for passengers' surviving and the residual space shall be preserved in the passenger compartment during and after the standard rollover accident situation. Rollover test and simulation on a large-sized bus was completed according to the regulation. The coordinates of the points on the bus were measured by photogrammetry system. The rollover situation was revived by structural crashes simulation software, PAM-CRASH, and it was checked that the structure still complied with the requirements of residual space during rollover situation. The residual space was preserved during rollover, so it was proved that the structure of the investigated bus had much probability of survival in rollover accidents.

• 한국자동차공학회논문집
• /
• 제9권4호
• /
• pp.176-183
• /
• 2001

It is difficult to find out the kinematic characteristics of a vehicle suspension without the usage of CAE software. The application of CAE software into suspension kinematics and dynamics yields the more precise knowledge on the chassis design. In this study, the influence of the suspension geometry on the handling performances of a large-sized bus is investigated using the DADS software. The front and rear suspension of a large-sized bus are a rigid axle suspension with the four control links. The elastokinematic analysis is performed to evaluate the roll characteristics of the front and rear suspension. The elastokinematic responses are evaluated in terms of the roll center height and roll steer for various geometric parameters. The roll center height is mainly dependent on the vertical displacement of a panhard rod and the vertical displacements of lower control links affect the roll steer of a rear suspension. The parameter study with the change of rear suspension geometry is conducted to investigate the vehicle handling performances. This parameter study shows that the vertical displacement and orientation of a panhard rod influence the handling performances of a large-sized bus significantly.

• 한국공작기계학회논문집
• /
• 제13권1호
• /
• pp.88-93
• /
• 2004

In general, a fundamental structural design consideration for an automobile is the overall dynamic behavior in bending and torsion. Dynamic behavior of the automobile are mainly influenced by the structural stiffness of B.I.W.(body-in-white) and the physical property of trim components. In this paper, the modeling techniques for various trim components of middle-sized bus are presented, and the dynamic effects of the trim components on the vibration characteristics of the bus are investigated. The $1^{st}$ torsional frequency is decreased by attaching windshield and backlite to the B.I.W., but the $1^{st}$ vertical bending frequency and the $1^{st}$ lateral bending frequency are increased. The natural frequencies of the bus are decreased by attaching doors and windows. And also, the natural frequencies of the bus are large decreased by attaching seats, instrument panel etc. The study shows that the dynamic characteristics of the bus can be effectively predicted in the initial design stage.

• 한국생산제조학회지
• /
• 제21권4호
• /
• pp.683-690
• /
• 2012

In this work, the semi-active control of a large-sized bus suspension system with an MR damper was studied. An MR damper model that can aptly describe the hysteretic characteristics of an MR damper was adopted. Parameter values of the MR damper model were suitably modified by considering the maximum damping force of a passive damper used in the suspension system of a real large-sized bus. In addition, a fuzzy logic controller was developed for semi-active control of a suspension system with an MR damper. The vertical acceleration at the attachment point of the MR damper and the relative velocity between sprung and unsprung masses were used as input variables, while voltage was used as the output variable. Straight-ahead driving simulations were performed on a road with a random road profile and on a flat road with a bump. In straight-ahead driving simulations, the vertical acceleration and pitch angle were measured to compare the riding performance of a suspension system with a passive damper with that of a suspension with an MR damper. In addition, a single lane change simulation was performed. In the simulation, the lateral acceleration and roll angle were measured in order to compare the handling performance of a suspension system using a passive damper with that of a suspension system using an MR damper.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
• /
• pp.9-12
• /
• 2008

For the large-sized and post-ultra definition TFT-LCD, improved drivability is prerequisite not only for the integration of driving circuit on glass but also for the chargeability of each pixel. In order to meet required drivability, currently adopted process architecture and materials are modified for the RC delay reduction, including the drastic increase of gate bus thickness and its related solution for step coverage. We present new process architecture and material selection for the next generation TFT-LCD devices.

• 한국자동차공학회논문집
• /
• 제13권2호
• /
• pp.16-21
• /
• 2005

The performance of reciprocating internal combustion engine is a strong function of the air intake system configuration. In order to improve engine power, it is essential to optimize the air induction system. In this study, a numerical investigation has been carried out for the three-dimensional flow and pressure characteristics in air intake system of a large-sized commercial bus. CFD simulations using STAR-CD were also perform ed to evaluate effects of intake duct geometry and structure variation inside air cleaner on the negative pressure distribution of overall intake system. Studies for improving the back pressure distribution have been proposed and quantitatively examined based on intensive case studies.

• 대한산업공학회지
• /
• 제17권2호
• /
• pp.51-61
• /
• 1991

This paper presents a heuristic method for the Assembly Line Balancing(ALB) of the large-sized product. In the ALB problem of the large-sized product such as bus and truck, the assignments of the Related Task Groups(RTG), the same side tasks, and team tasks should be considered. In this paper, a new concept of the RTG and two kinds of assignment rules are proposed to resolve the above considerations. The first assignment rule allots the RTG with the constraint of the same side tasks to the station while the second allots the RTG to the station, relaxing the above constraint to increase the applicability of the method. An assignment rule for team tasks is also presented. The benefits of the method are to improve work methods, to give more job satisfaction to workers, and to allow greater flexibility in the design of assembly lines.

• 한국자동차공학회논문집
• /
• 제11권2호
• /
• pp.126-133
• /
• 2003

The aerodynamic characteristics of automobiles have received substantial interest recently. Detailed knowledge of the vehicle aerodynamics is essential to improve fuel efficiency and enhance stability at high-speed cruising. In this study, a numerical simulation has been carried out for three-dimensional turbulent flows around a commercial bus body. Also, the effect of rear-spoiler attached at rear end of bus body was investigated. The Wavier-Stokes equation is solved with SIMPLE method in general curvilinear coordinates system. RNG $k-\varepsilon$ turbulence model with the MARS scheme was used for the evaluating aerodynamic forces, velocity and pressure distribution. The results showed details of the three-dimensional wake flow in the immediate rear of bus body and the effect of rear-spoiler on the wake structure. A maximum of 14% reduction in drag coefficient was achieved for a model with a rear-spoiler.

• 한국경영과학회지
• /
• 제17권1호
• /
• pp.55-65
• /
• 1992

There are takes performed on only one side (right side or left side) of the assembly line, and task groups in which the tasks are more related to one another like a subassembly. In the Assembly Line Balancing (ALB) of the large-sized product such as bus and truck, the side on which tasks are performed and the related task groups should be considered to improve work methods and to appropriately lay out parts and facilities in the line. In this paper, presented are the 0-1 programming formulations for the ALB with the constraints of assigning the same side tasks to the station. The objective of minimizing the number of stations is combined with the objective that the total number of the related task groups handled by all the stations is minimized. Also, proposed are the methods of reducing the number of variables and constraints, and of determining the station to which subassembly tasks are assigned.