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Technical Paper

The Prediction of Volumetric Efficiency Considering Gas Exchange Process in Spark Ignition Engine

The volumetric efficiency for a 4-stroke, single- cylinder, spark- ignition engine is considered. The mathematical model for the gas exchange process was formulated and solved by numerical technique. The mass flow rate, the pressure-time history in cylinder, intake and exhaust pipes, and the volumetric efficiency were calculated. The important parameter affecting volumetric efficiency was the pressure in the pipes. But, the effect of valve timing on volumetric efficiency was small (1, 2)*. The experiments with 3-different cams were performed. The predicted results were compared with experimental data and satisfactory agreement was obtained. As a result, the volumetric efficiency could be predicted with a relatively simple mathematical model.
Technical Paper

Application of Functional Design Method to Road Vehicle Aerodynamic Optimization in Initial Design Stage

Exterior shape of automobile can be represented by shape function through this study so that aerodynamic shape parameters can be easily controlled and changed. Also ordinary geometric information can be extracted easily from shape function model by simple calculations. It is possible to predict the aerodynamic performance of functional virtual car models which are transformed continually by developing automated program in initial design stage that includes all of above process. Innovative vehicle design process with exterior design guide will be proposed for stylist, engineer and packaging department in order to achieve low aerodynamic drag and high fuel efficiency targets.
Technical Paper

Biomechanical Discomfort Factors in Egress of Older Drivers

Discomfort models play a significant role in ergonomic simulation. More detailed and specific discomfort models are required for older drivers who represent the fastest-growing segment of the driving population. Owing to the physical degradation, various biomechanical discomfort factors should be incorporated into the model to properly evaluate discomfort for the older population group. In this experimental study we attempted to identify and quantify biomechanical factors that affect the older drivers' discomfort ratings. Different egress motion strategies (e.g., with and without using assist devices) were designed to induce various physical activities. The corresponding discomfort ratings were then produced. From the kinematic analysis using a digital human body model with reconstructed egress motion, the hip abduction was found to have the most statistically significant effect on the discomfort rating.
Technical Paper

Performance Design of Low Temperature Condenser for Waste Heat Recovery System

The optimum design process of the low-temperature condenser of a dual-loop waste heat recovery system with Rankine steam cycles for improving the fuel efficiency of gasoline automobiles has been investigated. The waste heat recovery system consists of a high-temperature (HT) loop in which water as the HT working fluid recovers waste heat only from the exhaust gas of about 700°C and a low-temperature (LT) loop in which a refrigerant as the LT working fluid recovers heat dissipation from the HT loop, and waste heat from the engine coolant of relatively low temperature. The low temperature condenser plays a role to dissipate heat from the system by condensing the low temperature loop working fluid sufficiently.
Technical Paper

Model Predictive Control based Automated Driving Lane Change Control Algorithm for Merge Situation on Highway Intersection

This paper describes design and evaluation of a driving mode decision and lane change control algorithm of automated vehicle in merge situations on highway intersection. For the development of a highly automated driving control algorithm in merge situation, driving mode change from lane keeping to lane change is necessary to merge appropriately. In a merge situation, the driving objective is slightly different to general driving situation. Unlike general situation, the lane change should be completed in a limited travel distance in a merge situation. Merge mode decision is determined based on surrounding vehicles states and remained distance of merge lane. In merge mode decision algorithm, merge availability and desired merge position are decided to change lane safely and quickly. Merge availability and desired merge position are based on the safety distance that considers relative velocity and relative position of subject and surrounding vehicles.
Technical Paper

Numerical Analysis on the Effect of Piston Bowl Geometry in Gasoline-Diesel Dual-Fuel Combustion

As emissions regulations become stricter, a variety of advanced combustion concepts that can reduce emissions with a higher thermal efficiency have been suggested. Dual-fuel combustion is one of the alternatives that has both premixed and non-premixed combustion characteristics. Knowing the effects of the mixture formation in dual-fuel combustion is important because it determines the ignition location and the following combustion phase. Hence, a thorough investigation on the related factors, such as the engine hardware or fuel spray, is required. Meanwhile, Computational Fluid Dynamics (CFD) is a good technique to visualize the in-cylinder phenomena and enables quantitative investigations into the detailed combustion characteristics. In this paper, a 3-dimensional CFD simulation was used to investigate the effects of the mixture formation in dual-fuel combustion. The combustion model consists of two parts.
Technical Paper

Analysis of an Automotive Ground System Based on a Ground Model and Current Distribution in it

Ground systems in automobiles become more important as more electric devices are installed and the amount of currents flowing increases. The performance of the devices depends on the ground voltage, which is generated between ground points by I-R voltage drops. Therefore, low ground voltages are required for the reduction of the unnecessary power dissipation as well as the reliable performance of the devices. In this paper, we propose an automotive ground system model to analyze ground structure and reveal the main cause of ground voltages. The equivalent resistor network model is presented to describe the relationship between ground points. Then, we validate the model by comparing the simulation results with the measurements in a real car. The presented analysis can provide guidance on designing a reliable ground system such as how to reduce the ground voltages for the proper operation of devices.
Technical Paper

Modeling of Unburned Hydrocarbon Oxidation in Engine Conditions using Modified One-step Reaction Model

Modeling of unburned hydrocarbon oxidation in an SI engine was performed in engine condition using modified one-step oxidation model. The new one-step equation was developed by modifying the Arrhenius reaction rate coefficients of the conventional one-step model. The modified model was well matched with the results of detailed chemical reaction mechanism in terms of 90 % oxidation time of the fuel. In this modification, the effect of pressure and intermediate species in the burnt gas on the oxidation rate investigated and included in developed one-step model. The effect of pressure was also investigated and included as an additional multiplying factor in the reaction equation. To simulate the oxidation process of piston crevice hydrocarbons, a computational mesh was constructed with fine mesh density at the piston crevice region and the number of cell layers in cylinder was controlled according to the motion of piston.
Technical Paper

Fatigue Life Analysis of Automotive V-belt Pulley

Fatigue life of a V-belt pulley, which is commonly used in automotive powertrain to transfer power to other parts, is predicted based on damage analysis by finite element analysis (FEA). Load conditions on pulley are analyzed by considering interactions among the pulley, V belt, bracket and bolts. Both normal force and traction force on the contact surfaces between the pulley and V belt were calculated. Assembly load due to the tightening of the bolts as well as operation load was considered to describe the actual load conditions in durability test. Static analysis at initial position of the pulley after assembly was performed with given load conditions. As the pulley rotated every ten degrees, consecutive static analyses were followed to find out the stress history of the pulley during operation. Using stress history data calculated from FE analysis, damage over one rotation of pulley was calculated and fatigue life, number of rotation to failure, was estimated.
Technical Paper

Measurements and Modeling of Residual Gas Fraction in SI Engines

The residual gas in SI engines is one of important factors on emission and performance such as combustion stability. With high residual gas fractions, flame speed and maximum combustion temperature are decreased and there are deeply related with combustion stability, especially at Idle and NOx emission at relatively high engine load. Therefore, there is a need to characterize the residual gas fraction as a function of the engine operating parameters. A model for predicting the residual gas fraction has been formulated in this paper. The model accounts for the contribution due to the back flow of exhaust gas to the cylinder during valve overlap and it includes in-cylinder pressure prediction model during valve overlap. The model is derived from the one dimension flow process during overlap period and a simple ideal cycle model.
Technical Paper

Three Dimensional Flow Field Simulation to Estimate Performance of a Torque Converter

This paper describes a simulation procedure to calculate a torque converter performance. The study focuses the validity of a solution and the handiness of the procedure. A comparison of the numerical solution and the experimental solution proves the model validity. Moreover, handiness is achieved by using commercial code with automatic unstructured mesh generating techniques. With suggested procedure, a complete analysis is carried out relatively fast. And an steady state interaction can be analyzed between three moving elements.
Technical Paper

Modeling of Proportional Control Solenoid Valve for Automatic Transmission Using System Identification Theory

As most of today's automatic transmissions adopt a electro-hydraulic control system, the role of electronically controlled solenoid valves occupies an important position. This paper presents a dynamic modelling technique of a proportional control solenoid valve(PCSV) for automatic transmissions in terms of the system identification theory, and analyzes the dynamic characteristics of the PCSV in frequency domain. Also we find that there are good matches between the nonlinear dynamic simulation results and the experimental data.
Technical Paper

The Study on the Optimization of Attachment Stiffness in Vehicle Body

The achievement of improved NVH performance with light weighted body and low cost is very important, but difficult job to be accomplished in vehicle development. One of the various methods for the accomplishment of this goal is the optimization of the stiffness attached to a vehicle body and chassis. It is known that sufficient stiffness at the body attachments improves the flexibility of bushing rate tuning. In this paper, the theoretical consideration and analysis tool to estimate local stiffness value quantitatively are introduced. Also, the local stiffness values at various attachment locations in trimmed body are measured. The operational forces at body attachments are estimated through the TPA (Transfer Path Analysis). The suitability of attachment stiffness is judged based on the required NVH target to attain the optimal attachment stiffness in vehicle body.
Technical Paper

Three Types of Simulation Algorithms for Evaluating the HEV Fuel Efficiency

In regard to the evaluation of the performance of a hybrid electric vehicle (HEV), there are as many simulation methods as there are developers or researchers. They adopt different operational algorithms and they use diverse techniques to realize their logic. However, the relation among the various simulation methods has not been clearly defined. Thus, it is not easy to choose a method that would bring the best consequences in the most efficient way. Here, we present three types of backward-looking simulation algorithms for evaluating the fuel efficiency of a power-split HEV. Then the results and cost-effectiveness of each algorithm are analyzed using various component ratings over a representative driving mode. Based on the comparative analysis, the algorithm that uses equivalent fuel consumption is shown to be highly cost-effective. Also, an inductive or empirical base is set up with the results for a component sizing methodology using the recommended simulation.
Journal Article

Adaptive Cruise Control with Collision Avoidance in Multi-Vehicle Traffic Situations

This paper presents a longitudinal control algorithm for an adaptive cruise control (ACC) with collision avoidance (CA) in multiple vehicle traffic situations. The proposed algorithm consists of a multi-target tracking filter, a primary target selection algorithm and an integrated ACC/CA system. The multi-target tracking filter is used to smooth the sensor signal, and makes it possible to apply to a control system. The primary target selection algorithm decides an in-lane target and provides the information to an integrated ACC/CA system in order to drive a subject vehicle smoothly and improve safety in complex traffic situations. Finally, the integrated ACC/CA system computes the desired acceleration. The performance and safety benefits of the multi-vehicle ACC/CA system is investigated via simulations using real data on driving. Simulation results show that the response of multi-vehicle ACC/CA system is more smooth and safer at a change of traffic situations.
Journal Article

Skid Steering Based Maneuvering of Robotic Vehicle with Articulated Suspension

This paper describes a driving control algorithm based on skid steering for a Robotic Vehicle with Articulated Suspension (RVAS). The driving control algorithm consists of four parts; speed controller for tracking of the desired speeds, yaw rate controller which computes a yaw moment input to track desired yaw rates, longitudinal tire force distribution which determines an optimal desired longitudinal tire force and wheel torque controller which determines a wheel torque command at each wheel to keep slip ratio at each wheel below a limit value as well as track the desired tire force. Longitudinal and vertical tire force estimators are designed for optimal tire force distribution and wheel slip control. The dynamic model of RVAS for simulation study is validated using vehicle test data.
Technical Paper

Wire Segment Error Locating Algorithm for Wiring Connection Verification Tool

Due to increasing amount of modules and customized options in commercial vehicles, it becomes more and more difficult to verify the circuit design. In this paper, a wire segment error locating algorithm is proposed to automate the exact wire segment error locating process. When a wrong connection is found by existing tool, guided by the exact description of wire segment error, this algorithm can locate exact wire segment error in the connection by searching for the one that has at least one neighboring segment from a correct connection.
Journal Article

Developing Mode Shift Strategies for a Two-Mode Hybrid Powertrain with Fixed Gears

Two-mode hybrid architectures with three planetary gear sets and four clutches will bring both flexibility and complexity to energy management of powertrains. In order to take full advantage of the increased degrees of freedom, highly delicate operation strategies are needed. We develop transmission efficiency models for power-split modes, and present a mode shift strategy assuming no battery power. When battery load leveling is additionally considered, the respective optimal operation set for each mode can be obtained and compared to yield a mode shift algorithm for general hybrid operation situations. The investigation of the strategies shows how frequently each mode is used, and verifies the effectiveness of fixed gear operations. We check the validity of the strategies by applying the algorithm to dynamic optimization and by predicting how it works during an actual driving simulation.
Technical Paper

Hydraulic Simulation and Experimental Analysis of Needle Response and Controlled Injection Rate Shape Characteristics in a Piezo-driven Diesel Injector

The More precise control of the multiple-injection is required in common-rail injection system of direct injection diesel engine to meet the low NOx emission and optimal PM filter system. The main parameter for obtaining the multiple-injections is the mechanism controlling the injector needle energizing and movement. In this study, a piezo-driven diesel injector, as a new method driven by piezoelectric energy, has been applied with a purpose to develop the analysis model of the piezo actuator to predict the dynamics characteristics of the hydraulic component (injector) by using the AMESim code and to evaluate the effect of this control capability on spray formation processes. Aimed at simulating the hydraulic behavior of the piezo-driven injector, the circuit model has been developed and verified by comparison with the experimental results.
Technical Paper

Development of Ground Level Simulation Tool for Automotive Applications

This paper describes the ground system model and algorithm for a ground level simulation tool. First, the modeling of an automotive ground system will be discussed and the algorithm for a simulation tool will be explained. We divided the model into a ground tree and a ground body. The ground tree model consists of resistance formed by the wires that connect the load to ground point with various structures and the ground body model consists of resistance between ground points in the car body. The wires with large current, such as engine ground cable, was modeled in detail by dividing the resistance into wire, bolt, and clamping resistance, in order to simulate the effect of increased contact resistance after durability test. The algorithm of the ground level simulation tool was designed to adjust the currents of the alternator, battery, and ground points in order to evaluate the various driving and load conditions.