Search Results

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.

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.

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.

Suspension system of vehicle is very important because it has an effect on ride comfort and safety. And the leaf spring is one of the major parts of commercial vehicle. By that reason it has to be designed to operate under severe condition to ensure enough endurance. But the traditional method for fatigue design needs repeated fatigue tests for each design according to its geometry, material, and operating condition. This means that a lot of time and money is needed for those tests. Thus, in this paper, a fatigue design method for leaf spring based on numerical analysis is proposed. At first, stress analysis is performed to get the stress under operation load or rig tests. And fatigue analysis is performed to get the fatigue life and to ensure the safety of leaf spring. Through this study, design parameters that play vital role in fatigue life of the leaf spring can be found out.

The use of light-weight materials in automotive engine components has increased in order to achieve better fuel efficiency and engine performance. In this study, Al alloy (AI5056) valve spring retainer can reduce a weight by 63% in comparison to steel and improve the upper limit of engine speed by about 500rpm. The Al valve spring retainer was fabricated by cold forging and coated with hard anodizing, DLC (diamond like coating), cold spray and thermal spray for better wear resistance and durability. We conclude that among these materials the DLC coating improves the wear resistance of Al valve spring retainer and has a sufficient durability after endurance testing.

In this paper, front and rear 5-link independent suspension systems are introduced which are developed for the Hyundai Genesis. The front suspension has two upper links, two lower links, and a tie-rod. In the rear suspension, there are two upper links, a lower link, a trailing link, and a toe control link. The design concepts of front and rear suspension systems are explained, respectively. Also, it is presented how the suspension characteristics are designed and optimized to satisfy the desired performances such as luxurious ride feeling and precise handling.

The Rollover CAE model is developed for Rollover sensing algorithm in this paper. By using suggested CAE model, it is possible to make sensing data of rollover test matrix and these data can be used for calibration of rollover sensing algorithm. Developed vehicle model consists of three parts: a vehicle parts, an occupant parts and a ground boundary conditions. The vehicle parts include detailed suspension model and FE structure model. The occupant parts include ATD (anthropomorphic test device) male dummy and restraint systems: Curtain Airbag and Seat-Belt. We find analytical value of the suspension model through correlation with vehicle drop test, simulate this model under the conditions of untripped (Embankment, Corkscrew) and tripped (Curb-Trip, Soil-Trip) rollover scenarios. Comparison of the simulation and experimental data shows that the simulation results of suggested CAE model can be substituted for the experimental ones in calibration of rollover sensing algorithm.

The automotive shock absorber has various functions in car performance. Particularly, it is a dominant tuning parameter to get good primary and secondary ride characteristics within 1-35Hz ranges in car development. Thus, understanding of characteristics of shock absorber in this frequency range is indispensable to both test and analysis engineers for an effective and systematic approach. In this study, tire is also investigated from the same point of view. Frequency dependent stiffness and damping coefficient are extracted by discrete sine swept test under constant velocity of 25, 50, 100mm/sec which represent typical road surface conditions[1]. The responses are analyzed on frequency domain and the basic theoretical background for this approach is introduced.

The mobility technique is used to analyze the transfer functions of road noise between the suspension and the body structure. In the previous analyses, the suspension system and the body structure are altogether modeled as subsystems in the noise transfer path. In this paper, the mobility between the suspension and the body structure is analyzed by the dynamic stiffness at the connecting points. The measured drive point acceleration FRF at the connecting point in the transfer path was used to estimate the contributions of subsystems. The vibration modes of tire, the acoustic noise of tire's interior cavity, the vibration modes of the car's interior room, and the vibrations of body structure and the chassis are also considered to analyze the coupling effects of the road noise. Analyzing the measured results, direction for modification of car components is suggested.

This paper presents a transient vibration analysis of a nonlinear full-vehicle. The full-vehicle model consists of a powertrain, a trimmed body, a drive line, and front and rear suspensions with tires. It is driven by combustion forces and runs on a road surface. By performing time-domain simulation, it is possible to capture nonlinear behavior of a vehicle such as preload due to gravitational force, large deformation, and material nonlinearity which cannot be properly treated in the conventional steady state analysis. In constructing a full-vehicle, validation process is essential. Validation process is applied with respect to the assembling sequence. The validation starts with component levels such as tires, springs, shock absorbers, and a powertrain, and then the full-vehicle model is constructed. Model validation is done in two aspects; one is model accuracy and the other is model efficiency.

This paper proposes a reference steering wheel torque map and a torque tracking algorithm via steer-by-wire to achieve the targeted steering feel. The reference steering wheel torque map is designed using the measurement data of rack force and steering characteristic of a target performance of the vehicle at transition steering test. Since the target performance of the vehicle is only tested in nominal road condition, various road conditions such as disturbances and tire-road friction are not considered. Hence, the measurement data of the rack force that reflects the road conditions in the reference steering wheel torque map have been used. The rack force is the net force which consists of tire aligning moment, road friction force and normal force on the tire kingpin axis. A motor and a magnetorheological damper are used as actuators to generate the desired steering feel using the torque tracking algorithm.

In general, the ride and handling characteristics of a vehicle are strongly dependent on chassis parameters that come from the kinematic and compliance properties of a suspension system. For ride comfort improvement of a compact SUV with increasing handling performance simultaneously, this research proposes a new quantitative approach by considering various driving maneuvers and road surfaces. Particularly, five different road surfaces were used for ride comfort analysis, and this analysis was performed for two different vehicle speeds on a cleat road profile and three different vehicle speeds on a rough road profile. The contribution analysis of a suspension and a seat structure to ride comfort was investigated in order to decide an optimal structural combination. It was shown that contribution of each factor is different according to road profiles and driving conditions respectively.

This paper describes a reference steering feel tracking algorithm for Electric-Power-Steering (EPS) system. Development of the EPS system with intended steering feel has been time-consuming procedure, because the feedforward map-based method has been applied to the conventional EPS system. However, in this study, a three-dimensional reference steering feel surface, which is determined from current vehicle states, is proposed. In order to track the proposed reference steering feel surface, sliding mode approach is applied to second-order steering dynamics model considering a coulomb friction model. An adaptive technique is utilized for robustness against uncertainties. In order to validate the proposed EPS control algorithm, hardware-in-the-loop simulation (HILS) has been conducted with respect to a typical steering test. It is shown that the reference steering feel is realized well by the proposed EPS control algorithm.

Road friction estimation algorithms had been studied for many years because it is very important factor for safety control and fuel efficiency of vehicle. But traditional solutions are hard to adapt in automotive industry because their performance is not sufficient enough and expensive to implement. Therefore, this paper proposes a road friction estimation algorithm based on a trained artificial neural-network which is low cost and robust. The suggested method doesn’t need expensive additional sensors such as optical or lidar sensor, also it shows better performance in real car environment compared to other algorithms based on vehicle dynamics. In this paper, we would describe this algorithm in detail and analyze the test results evaluated in real road conditions.

In this study, a co-operative regenerative braking control algorithm was developed for an electric vehicle (EV) equipped with an electronic wedge brake (EWB) for its front wheels and an electronic mechanical brake (EMB) for its rear wheels. The co-operative regenerative braking control algorithm was designed considering the road friction characteristic to increase the recuperation energy while avoiding wheel lock. A powertrain model of an EV composed of a motor, and batteries and a MATLAB model of the control algorithm were also developed. They were linked to the CarSim model of the vehicle under study to develop an EV simulator. The EMB and EWB were modeled with an actuator, screw, and wedge to develop an EMB and EWB simulator. A co-simulator for an EV equipped with an EWB for the front wheels and an EMB for the rear wheels was fabricated, composed of the EV and the EMB and EWB simulator.

High strength oil-tempered wire was developed to apply to light-weight valve spring for automotive engine. By adding Mo, V, B and Ni, tensile strength increased by 20% compared to the conventional oil-tempered wire. Higher tensile strength of wire enabled a constant of valve spring to lower by reducing the size of spring. As a result, reduction of spring constant lowers the load of spring, thereby enhancing fuel efficiency.

The purpose of this paper is to identify and reduce a knocking noise from a rear suspension. First, the characteristics of a knocking noise are analyzed experimentally in the frequency domain. It was found that the knocking noise of a passenger room and vibration at a lower arm, a subframe and a floor are strongly correlated. Second, the knocking noise sensitivity is strongly dependent on suspension dynamics characteristics. Moreover, the improvement of ride comfort and noise was achieved simultaneously based on simulation analysis, principle vehicle testing. A design parameter study shows that the trailing arm bush stiffness, shock absorber bump/rebound damping characteristics, floor stiffness and shock absorber insulator bushing are one of the most sensitive parameter to affect the suspension knocking noise. Finally, this paper shows how the suspension knocking noise and ride comfort can be improved considering handling performance.

Automotive OEMs have introduced a new development paradigm, modular architecture development, to improve diversity quality and production efficiency. It needs solid fundamentals of system-based performance evaluation and development for each system level and single component level. When it comes to NVH development, it is challenging to realize the modular concept because noise and vibration should be transferred through various transfer path consisting of many parts and systems, which interact with each other. It is challenging for a single system of interest to be evaluated independently of the adjacent parts and environments. In this study, a new system-based development process for a vehicle suspension was investigated by applying blocked force theory and FRF-based dynamic substructuring. The objective is to determine the better dynamic stiffness distribution of many bushes installed in a suspension system in the frequency range corresponding to road noise.

The method of Front End Auxiliary Drive (FEAD) system optimization can be divided into two ways. One is to use a mechanical device that decouples crank pulley from torsional vibration of crank shaft by using characteristics of spring. The other is to control belt tension through auto-tensioner in addition of alternator pulley device. Because the former case has more potential to reduce belt tension than the latter case, the development of mechanically decoupled crank pulley, despite of its difficulty of development, is getting popular among the industry. This paper characterizes latest crank pulley technologies, Crank Decoupler and Isolation Pulley, for torsional vibration reduction through functionality measurement result which composed of irregularity, slip, tensioner movement, belt span vibration, bearing hubload of idler and so on. Also it investigates their potential of belt tension reduction through steady state point fuel consumption test on dynamometer.

This paper introduces a newly developed suspension system for new Elantra model of Hyundai Motor Company which will be on the market this year. The new chassis of Elantra has been developed to give more driving pleasure and confidence to a driver. To achieve these driving targets, the suspension has been changed and finely adjusted to achieve better ride and handling performance compared with the previous generation. Especially, a new multi-link suspension which has two upper links has been developed. The kinematics and compliance characteristics have been contrasted to those of the previous model. Also, the crashworthiness and package efficiency has been considered without limitation of suspension performance. Based on the customer's voice of market, the suspension of new Elantra has tried to fit the all kind of the customer's demand.