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The adoption of the electronic controlled steering systems with new technologies has been extended in recent years. They have interactions with other complex vehicle subsystems and it is a hard task for the vehicle developer to find the best solution from huge number of the combination of parameter settings with track tests. In order to improve the efficiency of the steering system development, the authors had developed a steering bench test method for steering system using a Hardware-In-the-Loop Simulation (HILS). In the steering HILS system, vehicle dynamics simulation and the tie rod axial force calculation are required at the same time in the real-time simulation environment. The accuracy of the tie rod axial force calculation is one of the key factors to reproduce the vehicle driving condition. But the calculation cannot be realized by a commercial software for the vehicle dynamics simulation.

Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio for improving thermal efficiency and downsizing the engine based on fuel-efficient operating conditions are good examples of technologies for enhancing gasoline engine fuel economy. A direct-injection system is adopted for most of these engines. Direct injection can prevent knocking by lowering the in-cylinder temperature through fuel evaporation in the cylinder. Therefore, direct injection is highly compatible with downsized engines that frequently operate under severe supercharging conditions for improving fuel economy as well as with high compression ratio engines for which susceptibility to knocking is a disadvantage.

Technologies for improving the fuel economy of gasoline engines have been vigorously developed in recent years for the purpose of reducing CO2 emissions. Increasing the compression ratio is an example of a technology for improving the thermal efficiency of gasoline engines. A significant issue of a high compression ratio engine for improving fuel economy and low-end torque is prevention of knocking under a low engine speed. Knocking is caused by autoignition of the air-fuel mixture in the cylinder and seems to be largely affected by heat transfer from the intake port and combustion chamber walls. In this study, the influence of heat transfer from the walls of each part was analyzed by the following three approaches using computational fluid dynamics (CFD) and experiments conducted with a multi-cooling engine system. First, the temperature rise of the air-fuel mixture by heat transfer from each part was analyzed.

The adoption of electric vehicles (EVs) has been announced worldwide with the aim of reducing CO2 emissions. However, a significant increase in electricity demand by EVs might impact the stable operation of the existing power grid. Meanwhile, EV charging is acceptable to most users if it is completed by the time of the next driving event. From the viewpoint of power grid operators, flexibility for shifting the timing of EV charging would be advantageous, including making effective use of renewable energy. In this work, an EV model and simulation tool were developed to make clear how the total charging demand of all EVs in use will be influenced by future EV specifications (e.g., charge power) and installation of charging infrastructure. Among the most influential factors, EV charging behavior according to use cases and regional characteristics were statistically analyzed based on the real-world usage data of over 14, 000 EVs and incorporated in the simulation tool.

This paper proposes a method of estimating road friction and tire slip angle in a cornering maneuver. The method can estimate front tire road friction accurately at low lateral acceleration because it is based on the tire self-aligning torque (SAT) that exhibits high sensitivity to road friction at low slip angles. Road friction and tire slip angle, which are mutually interdependent, are estimated simultaneously using an extended Kalman filter designed around a model describing the relationship between road friction and SAT and a vehicle lateral dynamic model. The front tire SAT is calculated with a mathematical model that describes the torque transmission characteristics from the electric power steering torque to SAT. Therefore, the proposed method is readily applicable to production vehicles. Results of an experimental study show that the change in road friction is instantaneously estimated at low lateral acceleration.

For diesel engine, lower compression ratio has been demanded to improve fuel consumption, exhaust emission and maximum power recently. However, low compression ratio engine might have combustion instability issues under cold temperature condition, especially just after engine started. As a first step of this study, cold temperature combustion was investigated by in-cylinder pressure analysis and it found out that higher heat release around top dead center, which was mainly contributed by pilot injection, was the key factor to improve engine speed fluctuation. For further understanding of combustion in cold condition, particularly mixture formation near a glow plug, 3D CFD simulation was applied. Specifically for this purpose, TI (Time-scale Interaction) combustion model has been developed for simulating combustion phenomena. This model was based on a reasonable combustion mode, taking into account the characteristic time scale of chemical reactions and turbulence eddy break-up.

A robotic driver has been designed on the basis of an analysis of a human driver's action in following a given driving schedule. The self-learning algorithm enables the robot to learn the vehicle characteristics without human intervention. Based on learned relationships, the robotic driver can determine an appropriate accelerator position and execute other operations through sophisticated calculations using the future scheduled vehicle speed and vehicle characteristics data. Compensation is also provided to minimize vehicle speed error. The robotic driver can reproduce the same types of exhaust emission and fuel economy data obtained with human drivers with good repeatability. It doesn't require long preparation time. Thereby making it possible to reduce experimentation work in the vehicle development process while providing good accuracy and reliability.

Traction control systems (TCSs) serve to control brake pressure and engine torque, thereby reducing driving wheel spin for improved stability and handling. Systems are divided into two basic types by the brake control configuration. One type is a one-channel left-right common control system and the other is a two-channel individual control system. This paper presents an analysis of these two types of TCS configurations in terms of handling, acceleration, stability, yaw convergence and other performance parameters. The systems are compared with and without a limited-slip differential (LSD) under various road conditions, based on experimental data and computer simulations. As a result of this work, certain Nissan models are now equipped with a new Nissan Traction Control System with a rear viscous LSD (Nissan V-TCS), which provides both the advantages of a rear viscous LSD in a small slip region and a two-channel TCS in a large slip region.

Hydraulic engine mounts(HEM) are replacing conventional rubber mounts to provide better ride quality and to reduce noise. However, detailed analysis of the HEM is needed to predict ideal performance conditions. In this study, the optimum design of a HEM is modelled using design optimization theory for a dynamic absorber. After determining ideal behavior by simulation, an experimental mounts is designed and tested to verify the model.

Since interior noise has a strong effect on vehicle salability, it is particularly important to be able to estimate noise levels accurately by means of simulation at the design stage. The use of sensitivity analysis makes it easy to determine how the analytical model should be modified or the structure optimized for the purpose of reducting vibration and noise of the structural-acoustic systems. The present work focused on a structural-acoustic coupling problem. As the coefficient matrices of a coupled structural-acoustic system are not symmetrical, the conventional orthogonality conditions obtained in structural dynamics generally do not hold true for the coupled system. To overcome this problem, the orthogonality and normalization conditions of a coupled system were derived by us. In this paper, our sensitivity analysis methods are applied to an interior noise problem of a cabin model.

It is well known that the wheels and tires account for approximately 25% of the overall aerodynamic drag of a vehicle. This is because the contribution of the tires to aerodynamic drag stems from not only aerodynamic drag itself directly caused by exposure to the main flow (tire CD), but also from aerodynamic drag indirectly caused by the interference between tire wakes and the upper body flow (body CD). In the literature, as far as the authors are aware, there have been no reports that have included the following all four aspects at once: (1) CD sensitivity to detailed tire shape factors; (2) CD sensitivity differences due to different vehicle body types; (3) CD sensitivity for each aerodynamic drag component, i.e., tire CD and body CD; (4) Flow structure and mechanism contributing to each aerodynamic drag component. The purpose of this study was to clarify CD sensitivity to tire shape factors for tire CD and body CD considering two different vehicle body types, sedan and SUV.

This paper describes simultaneous attainment in improving fuel consumption, output power and reducing HC emissions with a direct injection S.I. engine newly developed in Nissan. Straight intake port is adopted to increase discharge coefficient under WOT operation and horizontal swirl flow is generated by a swirl control valve to provide stable stratified charge combustion under part load conditions. As a result, fuel consumption is reduced by more than 20% and power output is improved by approximately 10%. Moreover, unburned HC is reduced by equivalently 30% in engine cold start condition. An application of diagnostic and numerical simulation tools to investigate and optimize various factors are also introduced.

The Computer-Aided Principle (CAP) is applied in this study as an effective approach to the crashworthiness design of the vehicle front-end structure. With this method, correlative parameters are extracted in a parametric study by using a cluster analysis. The results can help engineers to understand the fundamental mechanisms of structural phenomena. A simulation example of an offset frontal crash against a deformable barrier (ODB) is presented to show the effectiveness of the proposed method.

Increasing expectations for stability at high speed call for the improvement of cars' aerodynamic performance, in particular lift reduction. However, due to styling constraints, traditional spoilers must be avoided and replaced by other solutions like underfloor components. Flow simulation is expected to be a useful tool for lift prediction, but the conventional models used so far did not represent complex geometry details such as the engine compartment and underfloor, and accuracy was insufficient. In the present study, a full vehicle simulation model, including the engine compartment and underfloor details, was used. Other improvements were also made such as optimization of the computational grid and the setting of boundary conditions for reproducing wind tunnel experiments or actual driving, making it possible to predict lift variations due to vehicle geometry changes.

This paper presents a new method for calculating optical flow using data from a high frame-rate camera. We focused on a feature of image data captured with a high frame-rate camera in which objects do not move more than one pixel between successive frames. This approach eliminates repetitive processing for object identification among frames taken at different sampling times. High-speed processing hardware architecture was designed with sequential processing only, and the algorithm was implemented in a field programmable gate array. The resultant unit can calculate optical flow for a 640×120 pixel size image with a 480-Hz processing cycle and 0.5-μsec processing latency.

Gasoline engines employ various mechanisms for improvement of fuel consumption and reduction of exhaust emissions to deal with environmental problems. Direct fuel injection is one such technology. This paper presents a new quasi-dimensional combustion model applicable to direct injection gasoline engine. The Model consists of author's original in-cylinder turbulence and mixture homogeneity sub model suitable for direct fuel injection conditions. Model validation results exhibit good agreement with experimental and 3D CFD data at steady state and transient operating conditions.

This paper describes the method used to design the basic control algorithm of a lane-keeping support system that is intended to assist the driver's steering action. Lane-keeping control has been designed with steering torque as the control input without providing a minor loop for the steering angle. This approach was taken in order to achieve an optimum balance of lane-keeping control, ease of steering intervention by the driver and robustness. The servo control system was designed on the basis of H2 control theory. Robustness against disturbances, vehicle nonlinearity and parameter variation was confirmed by μ - analysis. The results of computer simulations and driving tests have confirmed that the control system designed with this method provides the intended performance.

The Diesel Particulate Filter (DPF) system has been developed as one of key technologies to comply with tight diesel PM emission regulations. For the DPF control system, it is necessary to maintain temperature inside the DPF below the allowable service temperature, especially during soot regeneration to prevent catalyst deterioration and cracks. Therefore, the evaluation of soot regeneration is one of the key development items for the DPF system. On the other hand, regeneration evaluation requires a lot of time and cost since many different regeneration conditions should be investigated in order to simulate actual driving. The simulation tool to predict soot regeneration behavior is a powerful tool to accelerate the development of DPF design and safe regeneration control strategies. This paper describes the soot regeneration model applied to fuel additive and catalyzed types, and shows good correlation with measured data.

A transient knock prediction technique has been developed by coupling a zero-dimensional knocking simulation with chemical kinetics and a one-dimensional gas exchange engine model to study the occurrence of transient knock in SI engines. A mixed chemical reaction mechanism of the primary reference fuels was implemented in the two-zone combustion chamber model as the auto-ignition model of the end-gas. An empirical correlation between end-gas auto-ignition and knock intensity obtained through intensive analysis of experimental data has been applied to the knocking simulation with the aim of obtaining better prediction accuracy. The results of calculations made under various engine operating parameters show good agreement with experimental data for trace knock sensitivity to spark advance.

A new multidimensional calculation method has been developed to simulate the warm-up characteristics of close-coupled catalytic converter systems. First, a one-dimensional gas exchange simulation and a three-dimensional exhaust gas flow calculation are combined to simulate the pulsation gas flow caused by the gas exchange process. The gas flow calculation and a heat transfer calculation are then combined to simulate heat transfer in the exhaust manifold and the catalyst honeycomb under pulsation flow. The predicted warm-up characteristics of the systems examined agreed well with the experimental data. In this simulation, CPU time was reduced greatly through the use of new calculation methods. Finally, the warm-up process of close-coupled catalysts is analyzed in detail with this simulation method. The design requirements for improving warm-up characteristics have been made clear.