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The ways in which vehicles are used in the field are continually becoming more diverse. In order to provide the optimum solution with respect to performance and weight, it is necessary to be able to assure vehicle endurance reliability with a high degree of accuracy in relation to the manner of use in each market. This situation has increased the importance of accurately quantifying the ways in which vehicles are used in the field and of designing vehicles with sufficient endurance reliability to match the usage requirements. This report presents a “market model” by which the manner of usage in the field can be treated quantitatively using combinations of environmental factors that influence the road load, drive load and corrosion load, representing typical loads vehicles must withstand.

A safety support system that uses information received from the road infrastructure is being developed in a project sponsored by the Ministry of Land, Infrastructure and Transport. The purpose of this system is to reduce the number of accidents at intersections and on highways. The system is now being tested in an experimental vehicle. This paper describes what kind of information is helpful to drivers based on the experimental results.

This paper describes a process to achieve a pre-defined vehicle level interior sound quality target, by a sound engineering cascade to targeted noise and vibration development at the system level. Air-borne and structure-borne contributors to interior sound are identified at the system level using a comprehensive Transfer Path Analysis (TPA) in both the frequency and time domains. For significant contributors, the relative importance of the source system (powertrain) and path system (vehicle) are determined. System level changes are simulated, and their effect on interior sound evaluated using TPA. A set of feasible changes is identified that, when combined, achieves the vehicle level interior sound quality target. This set of changes defines system level targets for noise and vibration development, cascaded from the vehicle level target.

This paper deals with a vehicle detection method for realizing a blind spot warning function, under various environmental conditions. We introduced a method that is capable of discriminating the target object vehicles, under poor lighting conditions and in cases where the lens may be exposed to splashes in wet, snow and dirt roads. The image sensing of the vehicle detection consists of four functional components: obstacle detection, velocity estimation, vertical edge detection, and final classification. Such componets allow robust performances resembling geometry based approaches, with low calculation power as an apperance based approach. This paper describes the functional components, and furthermore methods to enhance the performances under low contrast conditions and also suppress false detections caused by residue on the lens, which becomes essential for installation on vehicles driven in actual road conditions.

In order to calculate efficiently the characteristics of car body vibration and the acoustic characteristic of the passenger compartment, a structural-acoustic analysis system, ‘CAD-B’, was developed. This system divides the body into three components - front body, main cabin and rear body. The characteristics of front and rear body vibration are expressed in modal parameters. The vibration characteristic throughout the car body is then calculated through the building block approach, while the main cabin remains in finite elements. A good agreement in eigen pairs was seen between this approach and the conventional finite element method. As for the passenger compartment, it is divided into finite elements and its eigen pairs are calculated. Then by linking body vibration with the acoustic characteristic of the passenger compartment, sound pressure in the passenger compartment is calculated.

Reduction of interior noise is an important factor in vehicle design and many experimental and theoretical studies have been carried out to find effective noise reduction techniques. Previously, we developed a Structural-Acoustic Uncoupled Program, ACOUST3, as a technique for estimating low-frequency noise in the vehicle interior. In the present work, ACOUST3 has been extended to construct an acoustic coupling analysis system, ASCA, which is used to calculate low-frequency noise, such as boom noise. In order to calculate low-frequency noise accurately, it is necessary to represent the vibration characteristics of the trimmed body as closely as possible. To do this, we built a trimmed body model, incorporating 22 trim parts, based on vibration test results, and found that the calculated results obtained with the model correlated well with experimental data.

In making driver workload assessments, it is important to evaluate the driver's level of brain activity because the operation of a motor vehicle presumably involves higher-order brain functions. Driving on narrow roads in particular probably imposes a load on the driver's brain functions because of the need to be cognizant of the tight space and to pay close attention to the surroundings. Test vehicles were fitted with a functional near-infrared spectroscopy (fNIRS) system for measuring bloodstream concentrations at 32 locations in the frontal lobe of the participating drivers in order to evaluate their levels of mental activity while driving on narrow roads. The results revealed significant increases in cerebral blood flow corresponding to the perceived workload. This suggests that increases in cerebral blood flow can be used as an effective index for estimating mental workloads.

Eliminating squeal noise generated during braking is an important task for the improvement of vehicle passengers' comfort. Considerable amount of research and development works have been done on the problem to date. In this study, we focused on the analyses of friction self-excited vibration and brake part resonance during high frequency brake squeal. Friction self-excited vibration is caused by the dry friction between pads and rotor, and occurs as a function of their relative sliding velocities. Its vibration frequency can be calculated in relation to the mass and stiffness of the pad sliding surface. Frequency responses of the brake assembly were measured and the vibration modes of the pad, disc and caliper during squeal were identified through modal analysis. Further study led to the development of a computer simulation method for analyzing the vibration modes of brake parts. Analytical results obtained using the method agreed well with the corresponding experimental data.

An analysis was made of vibration phenomena in the steering system of a vehicle, when the front wheels have some amount of unbalance. The program included vehicle running tests and bench tests to ascertain some of the factors influencing vibration behavior. A mathematical model of the vibration system was simulated on a digital computer in as much detail as possible. The resultant understanding of the dynamics of the system as a whole led to an extensive theoretical analysis of selected key parameters.

In order to demonstrate the generation mechanism of “combustion noise” separately from “mechanical noise,” the process of transfer in which vibration travels to each engine portion was analyzed through single-shot combustion of a propane-air mixture in the combustion chamber with the crankshaft fixed at a given angle. The effect of the natural frequency of each portion of the engine on the vibration transfer characteristics is discussed by introducing a vibration transfer function. The transfer paths of exciting forces which are caused by the combustion are quantitatively clarified.

Evaluations of dummy injury readings obtained in regulatory crash tests and new car assessment program tests provide indices for the development of crash safety performance in the process of developing new vehicles. Based on these indices, vehicle body structures and occupant restraint systems are designed to meet the required occupant injury criteria. There are many types of regulatory tests and new car assessment program tests that are conducted to evaluate vehicle safety performance in side impacts. Factoring all of the multiple test configurations into the development of new vehicles requires advanced design capabilities based on a good understanding of the mechanisms producing dummy injury readings. In recent years, advances in computer-aided engineering (CAE) tools and computer processing power have made it possible to run simulations of occupant restraint systems such as side airbags and seatbelts.

The target performance of a new engine has to be obtained under various restrictions such as cost and weihgt. It is particularly important to predict the engine noise and vibration performance at an early stage. For this purpose the analytical methods have been developed, which include the prediction of the absolute noise and vibration level by inputting a given exciting force into the model. These methods were applied to the development of the new engine. As a result, the characteristics of an aluminum cylinder block were used effectively to achieve a new lightweight V6 engine with low noise and vibration levels.

The progress of computer technology and CAE methodology makes it possible to simulate dummy injury readings in vehicle crash simulations. Dummy neck injuries are generally more difficult to simulate than injuries to other regions such as the head or chest. Accordingly, improving the accuracy of dummy neck injury data is a major concern in frontal occupant safety simulations. This paper describes the use of an advanced airbag modeling methodology to improve the accuracy of dummy neck injury readings. First, the following items incorporated in the advanced airbag model are explained. (1) The Finite Point Method (FPM) is used to simulate the flow of gas. (2) A folding model is applied to simulate the folded condition. (3) The fabric material properties used in the simulation take into account anisotropy in the fiber directions and the nonlinear, hysteresis characteristics of stiffness.

Curbing emissions of carbon dioxide (CO₂), which is believed by many scientists to be a major contributor to global warming, is one of the top priority issues that must be addressed by automobile manufacturers. Automakers have set their own strategies to improve fuel economy and to reduce CO₂ emissions. Some of them include integrated approaches, focusing on not only improvement of vehicle technology, but also human factors (eco-driving support for drivers) and social and transportation factors (traffic management by intelligent transportation systems [ITS]). Among them, electric vehicles (EVs) will be a key contributor to attaining the challenging goal of CO₂ reduction. Mass deployment of EVs is required to achieve a zero-emission society. To accomplish that, new advanced technologies, new business schemes, and new partnerships are required.

A simulation system has been developed for making comprehensive predictions and assessments of the various and interrelated indices of vehicle performance. This system draws upon a data base containing information on the characteristics of the different units making up a vehicle. The system includes fuel economy and emissions calculation programs incorporating a large number of evaluation items. It also features an acceleration calculation program by which the transient characteristics of a turbocharger can be studied and a vehicle exterior noise program that makes accurate predictions of the pass-by noise level during acceleration. Equipped with a large number of calculation functions the system is an effective tool for improving total vehicle performance.

After the turn of the century, growing social attention has been paid to environmental concerns, especially the reduction of greenhouse gas emissions and it comes down to a personal daily life concern which will affect the purchasing decision of vehicles in the future. Among all the sources of greenhouse gas emissions, the transportation industry is the primary target of reduction and almost every automotive company pours unprecedented amounts of money to reengineer the vehicle technologies for better fuel efficiency and reduced CO2 emission. Besides those efforts paid for sheer improvements of genuine vehicle technologies, NISSAN testified that “connectivity” with outside servers contributed a lot to reduce fuel consumption, thus the less emission of GHG, with two major factors; 1. detouring the traffic congestions with the support of probe-based real-time traffic information and 2. providing Eco-driving advices for the better driving behavior to prompt the better usage of energy.

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.

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.

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.

This paper describes the motor and inverter system developed for the Nissan LEAF that has been specifically designed as a mass-produced electric vehicle. The system produces maximum torque of 280 Nm and maximum power of 80 kW. The motor achieves a small size, high power, and high efficiency as a result of adopting the following in-house technologies. The magnetic circuit design was optimized for an interior magnet synchronous motor to attain the maximum performance figures noted here. The material technologies of the rotor and the stator facilitate high efficiency and the production technology achieves high density winding. The cooling mechanism is optimally designed for a mass-produced electric vehicle. The inverter incorporates the following original technologies and application-specific parts to obtain cost reductions combined with reliability improvements. The power module has an original structure with the power devices mounted directly on the busbars.