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In the analysis for durability or R&H performance with the full vehicle multibody models, the need for component flexibility is increasing along with demand for more precise full vehicle system. The component elastic deformations are usually expressed by modal superposition from component normal mode analysis with finite element model for reducing model size and simulation time. Although the simulation results of MBD analysis are more accurate according to increasing the number of flexible body and modes, the increasing of flexible components makes worse simulation time and convergence in MBD analysis. Especially, in the MBD analysis including a flexible upper body, in substitution for large number degree of freedom FE model such as trimmed body, it should take a few times longer than the case of rigid upper body This paper proposes the methods of reducing computational cost with adequate mode selections without the loss of simulation accuracy in the flexible MBD.

The assessment of the Transmission Loss (TL) of vehicle components at Low-Mid Frequencies generally raises difficulties associated to the physical mechanisms of the noise transmission through the automotive panel. As far as testing is concerned, it is common in the automotive industry to perform double room TL measurements of component baffled cut-outs, while numerical methods are rather applied when prototype or hardware variants are not available. Indeed, in the context of recent efforts for reduction of vehicle prototypes, the use of simulation is constantly challenged to deliver reliable means of decision during virtual design phase. While the Transfer matrix method is commonly and conveniently used at Mid-High frequencies for the calculation of a trimmed panel, the simulation of energy transfer at low frequencies must take into account modal interactions between the vehicle component and the acoustic environment.

It is known that SEA is a rapid and simple methodology for analyzing complex vibroacoustic systems. However, the SEA principle is not always valid and one has to be careful about the physical conditions at which the SEA principle is acceptable. In this study, the appropriate damping loss factor of the vehicle interior cavity is studied in the viewpoint of the modal overlap factor of the cavity and the decay per mean free path (DMFP) of the cavity. Virtual SEA tests are performed with an FE model combination, which is suggested by a previous study of Stelzer et al. for the simulation of the sound transmission loss (STL) of vehicle panel structure. The FE model combination is consisting of the body in white (BIW), an acoustical-excited hemisphere-shaped exterior cavity, and the interior cavity. It is found that the DMFP of the interior cavity is appropriate between 0.5 ~ 1 dB for applying SEA principle.

This paper presents a tire slip-angle based speed control race driver model. In developing a chassis control system for enhancement of high-speed driving performance, analysis of the vehicle-driver interaction at limit handling is one of the main research issues. Thus, a driver model which represents driving characteristics in a racing situation is required to develop a chassis control system. Since a race driver drives a vehicle as fast as possible on a given racing line without losing control, the proposed driver model is developed to ensure a lateral stability. In racing situation, one of the reasons which cause the lateral instabilities is an excessive corner-entry speed. The lateral instability in that moment is hard to handle with only a steering control. To guarantee the lateral stability of the vehicle while maximizing a cornering speed, a desired speed is determined to retain a tire slip-angle that maximizes lateral tire forces without front tire saturation.

High-voltage battery system plays a critical role in eco-friendly vehicles due to its effect on the cost and the electric driving range of eco-friendly vehicles. In order to secure the customer pool and the competitiveness of eco-vehicle technology, vehicle electrification requires lowering the battery cost and satisfying the customer needs when driving the vehicles in the real roads, for example, maximizing powers for fun drive, increasing battery capacities for achieving appropriate trip distances, etc. Because these vehicle specifications have a critical effect on the high-voltage battery specification, the key technology of the vehicle electrification is the appropriate decision on the specification of the high-voltage battery system, such as battery capacity and power. These factors affect the size of battery system and vehicle under floor design and also the profitability of the eco-friendly vehicles.

Fuel sloshing noise is involved with flow motion inside fuel tanks as well as structural characteristics of vehicles. Therefore it is necessary to introduce Fluid-Structure Interaction (FSI) analysis to predict sloshing noise phenomena more accurately. Purposes of this paper are to verify the reliability of the FSI method and suggest new CAE analysis processes to predict fuel sloshing noise. The vibration of floor panels induced by sloshing impact is evaluated through FSI analysis. A series of tests is carried out to validate simulation results. The numerical optimization of parameters is also carried out to reduce computation time. In addition, effects of sloshing noise factors are discussed based on simulation and test results. Lastly, a method to predict fuel sloshing noise by exerting sloshing load on a vehicle is suggested.

Passenger fatigue during long distance driving is greatly influenced by the comfort performance of the seat. Seat comfort performance is determined by the appropriate contour of the seat and the appropriate pad with sufficient thickness. The height of vehicle has been lowered to enhance car styling, and battery for electric vehicle applied to the underbody of the vehicle, reducing the package space of the seat in the vehicle. These external factors eventually lead to a reduced pad thickness of the seat cushion and compromise one of the important components in the seat cushion compartment, creating an uncomfortable cushioning problem when driving long distances. To improve the cushion composition of the seat within a limited package, air bladders are applied to the underside of the cushion pad. In addition, the function to support the buttocks using the air bladders of the lower cushion, similar to lumbar support for the back, was implemented to improve cushion comfort performance.

In this study, the preliminary validation method of the steering system is constructed and the objective is to satisfy the target performance in the conceptual design stage for minimizing the problems after the detailed design. The first consideration about steering system is how to extract the reliable steering effort for parking. The tire model commonly used in MBD(Multi-Body Dynamics) has limited ability to represent deformations under heavy loads. Therefore, it is necessary to study adequate tire model to simulate the behavior due to the large deformation and friction between the ground and the tire. The two approaches related with F tire model and mathematical model are used. The second is how to extract each link’s load in the conceptual design stage. Until now, each link’s load could be derived only by actual vehicle test, and a durability analysis was performed using only pre-settled RIG test conditions.

The windshield is an integral part of almost every modern passenger car. Combined with current developments in the automotive industry such as electrification and the integration of lightweight material systems, the reduction of interior noise caused by stochastic and transient wind excitation is deemed to be an increasing challenge for future NVH measures. Active control systems have proven to be a viable alternative compared to traditional passive NVH measures in different areas. However, for windshield actuation there are neither comparative studies nor actually established actuation concepts available to the automotive industry. This paper illustrates a comparative conceptual study on windshield actuation for the active control of wind noise in a passenger car. Making use of an experimental modal analysis of the windshield installed in a medium-sized vehicle, a reduced order numerical simulation model is derived.

In this research, the influence of tire size and shape on sound radiation in the mid-frequency region was studied. First, the relationship between the structural wave propagation characteristics of a tire excited at one point and its sound radiation was identified by using FE and BE analyses. Then, by using that relationship, the effect of modifying a tire's aspect ratio, width and wheel diameter on its sound radiation between 300 Hz and 800 Hz was investigated. Finally, an optimization of the sound radiation was performed by modification of the tire structure and shape. It was found that most of a tire's structural vibration does not contribute to sound radiation. In particular, the effective radiation was found to occur at the frequencies where low wave number components of the longitudinal wave and the flexural wave first appear.

In order to understand the automotive PEM fuel cell system, mathematical system modeling is conducted and the model is implemented and simulated by using the Matlab®/Simulink®. The components such as fuel cell stack, air supplier, and radiator are modeled individually and integrated into a system level. The PEM fuel cell system operation control includes thermal management, air supply control, hydrogen supply control, fuel cell stack protection control, and load following control. In the thermal management, the inlet and outlet temperature of coolant are controlled to operate the fuel cell stack in desired temperature range and to prevent flooding inside the fuel cell stack. In air supply control and hydrogen supply control, the flow rates of air and hydrogen are controlled not to starve the fuel cell stack according to the output current. A control structure for the system is developed and confirmed by using the developed simulation model.

The alternator provides power to vehicle electrical loads with the battery, and its maximum current depends on various factors such as electrical load, engine speed, thermal condition, and other variables. Above all, thermal effects make alternator simulations more complicated. For example statically similar conditions may show different results according to the temperature variation for each alternator operation. This paper proposes a two-stage statistically-based model structure which separates dynamic thermal effects from steady state performance. The method was validated by experiments and shows good predictive performance, suitable for use in test reduction.

Numerous machine elements are operated in mixed lubrication regime where is governed by a combination of boundary and fluid film effects. The direct contact between two surfaces reduces a machines life by increasing local pressure. In order to estimate machine's life exactly, the effect of asperity contact should be considered in the lubrication model. In this study, new 3-dimensional partial elasto-hydrodynamic lubrication (PEHL) algorithm is developed. The algorithm contains the procedures to find out solid contact regions within the lubricated regime and to calculate both the pressure by fluid film and the contact pressure between the asperities of the solids. Using the algorithm, we conducted the PEHL analysis for the contact between the rotating shaft and the inside of pinion gear. To investigate the effect of surface topology two different surfaces with sinusoidal profile are used. Both film thickness and pressure are calculated successfully through the PEHL algorithm.

A study for improving the resistance to fretting corrosion of SCr 420 pinion gear was conducted. Fretting is the damage to contacting surfaces experiencing slight relative reciprocating sliding motion of low amplitude. Fretting corrosion is the fretting damage to unlubricated contacting surfaces accompanied by corrosion, mostly oxidation that occurs if the fretting occurs in air. Two kinds of conventional heat treatment and a newly designed one suggested for improving the resistance to the fretting corrosion of pinion gear were compared each other to find out what is the main factor for generating fretting corrosion phenomenon. Increased carbon potential at both the heating and diffusing zone and reduced time of tempering was found out to be a solution for improving the resistance to fretting corrosion of forged and heat treated gear steel. On the contrary, modified carbo-nitriding using ammonia gas has been getting worse the fretting corrosion problem.

This paper proposes a modeling technique which is able to not only reliably and easily represent the hysteretic characteristics but also analyze the dynamic stress of a taper leaf spring. The flexible multi-body dynamic model of the taper leaf spring is developed by interfacing the finite element model and computation model of the taper leaf spring. Rigid dummy parts are attached at the places where a finite element leaf model is in contact with an adjacent one in order to apply contact model. Friction is defined in the contact model to represent the hysteretic phenomenon of the taper leaf spring. The test of the taper leaf spring is conducted for the validation of the reliability of the flexible multi-body dynamic model of the taper leaf spring developed in this paper. The test is started at an unloaded state with the excitation amplitude of 1∼2mm/sec and frequency of 132mm. First, the simulation is conducted with the same condition as the test.

3D digital human modeling (DHM) tools for vehicle packaging facilitate ergonomic design and evaluation based on anthropometry, comfort, and force analysis. It is now possible to quickly predict postures and positions for drivers with selected anthropometry based on ergonomics principles. Despite their powerful visual representation technology for human movements and postures, these tools are still questioned with regard to the validity of the output they provide, especially when predictions are made for different populations. Driving postures and positions of two populations (i.e. North Americans and Koreans) were measured in actual and mock-up SUVs to investigate postural differences and evaluate the results provided by a DHM tool. No difference in driving postures was found between different stature groups within the same population. Between the two populations, however, preferred angles differed for three joints (i.e., ankle, thigh, and hip).

Shudder vibration of a hydraulic power steering system during parking maneuver was studied with numerical and experimental methods. To quantify vibration performance of the system and recognize important stimuli for drivers, a shudder metric was derived by correlation between objective measurements and subjective ratings. A CAE model for steering wheel vibration analysis was developed and compared with measured data. In order to describe steering input dependency of shudder, a new dynamic friction modeling method, in which the magnitude of effective damping is determined by average velocity, was proposed. The developed model was validated using the measured steering wheel acceleration and the pressure change at inlet of the steering gear box. It was shown that the developed model successfully describes major modes by comparing the calculated FRF of the hydraulic system with measured one from the hydraulic excitation test.

The efficiency of a gap-type of deflector for suppressing vehicle sunroof buffeting is studied in this work. Buffeting is an unpleasant low frequency booming caused by flow-excited Helmholtz resonance of the interior cabin. Accurate prediction of this phenomenon requires accounting for the bi-directional coupling between the transient shear layer aerodynamics (vortex shedding) and the acoustic response of the cabin. Numerical simulations were performed using a CFD/CAA numerical method based on the Lattice Boltzmann Method (LBM). The well established LBM approach provides the time-dependent solution to the compressible Navier-Stokes equations, and directly captures both turbulent and acoustic pressure fluctuations over a wide range of scales given adequate computational grid resolution. In this study the same gap-type deflector configuration is installed on two different types of vehicles, a SUV and a sedan.

Luxury sound is one of the most important sound qualities in a premium passenger car. Previous work has shown that, because of the effects of many different interior sounds, it is difficult to evaluate the luxury sound objectively by using only the A-weighted sound pressure level. In this paper, the characteristics of such sound were first investigated by a systematic approach and a new objective evaluation method for luxury sound-the luxury sound quality index--which was developed by the systematic combination of the seven major interior sound quality indexes based on path analysis. The seven major sounds inside a passenger car were selected by a basic investigation evaluated by the members of a luxury automotive club. Seven major interior sound quality indexes were developed by using sound metrics, which are the psychoacoustic parameters, and the multiple regression method used for the modeling of the correlation between objective and subjective evaluation.

For a complete automotive HVAC system, it is desirable to keep good air quality control for the interior vehicle cabin. This experimental study for evaluating the CO2 concentration levels in a vehicle cabin was done on the roads in South Korea. Increasing levels of CO2 can cause a passenger to become tired, sleepy and cause headaches or discomfort. The study results shows that CO2 and fine dust concentration is a result of the number of passengers,_driving condition and HVAC user settings. The result from this investigation can be used to establish a development guide for air quality in a vehicle cabin.