The azimuth angle feedback steering system shows enhanced performance in the situation where quick steering action is necessary but it reauires continuous steering angle increments during turning, which results in some additional workload on drivers. Introducing yaw velocity feedback into the system enables the system to redeuce the steering wheel angle increments and the yaw velocity demping. As a result the system can reduce drevers' workload and improve course following performance. The performances of the generalized azimuth angle feedback steering system incorporated into a vehicle with actual response delay are evaluated multilaterally in this second report.

View full abstract

3DOF vehicle models that consider vehicle roll motion have been proposed, because roll motion significantly impacts the transient behavior of the vehicle. Previous model concepts, however, have a common problem that any modification of roll axis inclination angle automatically influences the roll steer characteristics. The thesis points out the problem and proposes a new model concept, which solves the porblem.

View full abstract

With the increasing demand for improvements in ride comfort, rolling or lateral vehicle behvior is now as important as bounce or pitching behavior. In this paper vehicle behaviors over rough roads are analyzed by dynamics motion equations with additional specific road input. After consideration of this analysis model, it is confirmed that suspension and tire characteristics should be divided into slip angle change due to lateral force and that due to vertical force or stroke. Also, the effects of each characteristic to vehicle behavior are clarified at each vehicle velocity range by both calculations and experiments.

View full abstract

A four-wheel vehicle with a roll axis above center of gravity of the sprung mass can roll inward in a turn. The high roll axis vehicle equipped with new suspensions is compared by full vehicle model simulations with a conventional low roll axis vehicle for ride quality and controllability. In consequence, the only problem of the high roll axis vehicle is that the lateral acceleration of sprung mass on a rough road increases nearly double as low axis model. Because other performances are the same level, the high roll axis vehicle is feasible enough.

View full abstract

It is known that stick-slip in serpentine belt causes squeal noise, but the whole aspect of the noise is not made clear and trial and error measures are adopted in belt design. In this paper the noise under unsteady running condition of an engine such as start and stop is studied mainly and it is made clear that generation of the noise under steady condition depends on friction-velocity characteristic and depends on tension-velocity characteristics under unsteady condition. Then a new concept to evaluate generation and level of the noise is introduced and shown to explain well experimental results.

View full abstract

It is thought that the innovation of ignition system becomes more important toward the relization of ultra-lean combustion for gasoline engine. In this study, High Speed plasma Ignition as the new ignition system for internal combustion engine was investigated. The high speed plasma is non-thermal plasma formed by impression of a high voltage with ultra-short duration between coaxial cylindrical electrodes. As the result of varification experiment by using a single cylinder engine, a volumetric ignition with low energy consumption was realized. Also, an improvement of ignitability in comparison with a conventional spark plug was confirmed.

View full abstract

When the auto-ignition combustion is applied to the two-stroke engines for the practical vehicle use, irregular combustion in the light loads generally would be the chief problem. This paper presents a new solution method for this problem, which was developed on the basis of the consideration on the in-cylinder gas behavior aspect. A stratified charge concept was introduced and examined in a two-stroke engine running with the auto-ignition state and the experiment has shown the following results. 1)Auto-ignition operating area is remarkably enlarged toward the lower load, 2)HC emissions are decreased, 3)fuel consumption and NOx emissions remain the same level, in comparison with those in the conventional auto-ignition with the homogeneous charge.

View full abstract

Improvement in output power and indicated thermal efficiency were achieved by lowering compression ratio from 13:1 to 11:1 hydrogen HCCI engine supported by DME supplement. Improved output power was realized by the truth that mitigated HCCI combustion derived by lowered compression ratio enabled stable HCCI combustion without showing any knocking inλof close to 2, which is much richer than 2.7 that is limited by knocking in compression ratio of 13:1. Improved indicated thermal efficiency was achieved by the ratarded onset of heat release around 1 to 3 deg. CA compared with compression ration of 13:1 and resulted in reduced heat loss to the cylinder wall. On the contrary, since misfiring limit was also shifted to the richer mixture region, stable operating range was not always expanded.

View full abstract

Complexity of the modern diesel engine has increased to meet the stringent future regulation of exhaust emissions and fuel consumption. Air management system including Exhaust Gas Recirculation(EGR), turbocharger and Variable Valve Action(VVA) system must be optimized of its design and control algorithm for combustion improvement coupled with precision control of fuel injection. Optimization of after treatment system, as a matter of course, is of extreme importance for exhaust emission reductin. However an enormous amount of energy will be required to develop such kind of complex engine system by actual testing. Therefore the Total Engine Simulation System(TESS) with zero-dimentsional combustion model based on phenomenalism was developed for investigation of future diesel engine system and its control logic. Premixed Compression Ignition(PCI) combustion would be a key technology for simultaneous reduction of exhaust emission and fuel consumption. Therefore the combustion model of the TESS was improved to predict PCI combustion in this study.

View full abstract

For measurement of very low diesel exhaust PM emissions, the filter gravimetric method may no longer be sufficiently accurate due to evaporation of filtered particles from or adsorption of condensable gases onto the filter media. For more accurate determination of the low emissions, we have been developing a technique based on the DMA (Differential Mobility Analyzer) and APM (Aerosol Particle Mass Analyzer) method. The results of somparison measurement between DMA-APM (online) method and filter gravimetric method show that the mass concentration by filter gravimetric method indicates lower value about 15% compared with online mothod.

View full abstract

AIST has conducted joint research with MTEC/NSTDA and TISTR for the standardizatin and upgrading of biodiesel fuel. Palm oil methyl ester from crude palm oil(crude PME) which was made in Thailand was used as a test fuel, and fuel property, material compatibility and emission characteristic were evaluated. By coexisting metal material, oxidation dagradation of crude PME accelerated. Especially, copper significantly accelerated degradation of PME. The influence of zinc on oxidation degradation is not so strong compared with other metal material, however zinc itself was found to be corroded by crud PME. For the emission characteristics, CO and THC decreased by blending crude PME. NOx emission increases with the incrase of crude PME by high engine load. PM emission increases by blending crude PME at low engine load.

View full abstract

In this study, the effects of initial gas conditions on diesel combustion are investigated by multi-dimensional computational fluid dynamins(CFD) code coupled with complex chemistry analysis. The first report examines the validity of the analysis, so the results of the numerical analysis, fuel injectin timing and EGR ratio was changed as a parameter, are compared with those of experiments. The results of the numerical analysis showed that this kind of analysis can predict in-cylinder pressure and heat release rate diagram and Nox emissions in good accuracy under various operating conditions.

View full abstract

This paper compares results via Reynolds stress model (RSM) with those via standard k-εmodel (KEM) for the flow field around the ASMO vehicle body. Positive diffusion is maintained for RSM by applying eddy viscosity type isotropic model. RSM shows a better body surface pressure distribution and C_D than KEM. Secondly, effects of three imitated underbody configurations, i.e.,exhaust pipe, rear suspension and tire house, on C_D value of the vehicle are clarified both via RSM and KEM. A rough underbody configuration does not necessarily increase C_D value compared with flat underbody, showing possibility of the detailed optimization approach for a better underbody configuration.

View full abstract

The study aims to classify aged drivers into several groups based on their driving characteristics. Such categorizing will be useful both for development of driver assistance syatems and for driver education. We classified them depending on their driving behavior nad background(physical and lifestyle) data. We also proposed quantitative classification method using driving parameters gained through driving simulator. Linear discriminant analysis showed it is possible to classify them into four groups with correct rete 79%. After varification of the method, the paper tried to apply it to driver assistance systems as one of examples using driving simulator.

View full abstract

An evaluation method is difficult to design a vehicle demension in order to improve the usability of ingress-egress. In this paper, from movement of the waist and hip joint in egress and ingress, the characteristics of physical workload of the pelvis-circumference are clarified. The authors have proposed an evaluation method by estimation the each part o joint moment in place of the evaluation of measuring the muscles of the pelvis-circumference. The experiments are carried out using mock-up of passenger car to verify the effectiveness of the proposed method of workload estimation in egress and ingress from vehicle dimensions.

View full abstract

In a previous study, we developed and validated a new driving posture fucused on biomechanical loads for physical fatifue reduction by biomechanical analysis and long-term driving. In this study, the posture was eveluated i dynamic long-term driving condition by qualitative and quantitative measurements. The results showed physical fatigue of the new posture was halved in comparison with the one of the conventional posture in same car configuration by subjective evaluations. Physiological indices had same tendency with subjective evaluations. From the results, we extracted seven physiological indices as good measures of physical fatigue while driving. Therefore, fatifue reduction of the new posture was qualitatively validated by physilogical mreasurements.

View full abstract

We developed a simulation system of driver's field of view on the basis of a binocular visual field model for ascertaining what visual information is available to a driver. A binocular visual fiel model describes standardized achromatic/chromatic contrast sensitivity properties as a function of retinal eccentricity. Simulated images are expected to exhibit some difference among retinal eccentricities, or among driving situations. We can evaluate visibility or conspicuity of many constituent objects of the visual world, which is the bottom-up factor governing a driver's visual behavior. Moreover we can predict that a moving driver experiences fundamental difficulty in detecting moveing objects, such as other cars or pedestrians, which was verified by psychophysical experiments.

View full abstract

It is necessary to improve the occupants' safety in crashes between different type vehicles(e.g., between SUVs and sedan-type vehicles). Formerly, authros analyzed the frontal collision between same weight SUV and sedan, by the statistical traffic accident data stored in ITARDA (Institute for Traffic Accident Research and Data Analysis), and confirmed that, regardless of same weight, the rate of fatal or severe injuries of SUV drivers in lower than that of sedans. So, in this paper, authors tried the analysis for other weight combination (e.g., light SUV to heavy sedan collision or heavy SUV to light sedan collision, ets.), to see the general tendency of SUV to sedan collision. From the tendency of drivers' injuty, in this analysis, we presumed that upper part of sedan cabins are crushed by front-end of SUVs depended of the vertical offset configuration between SUVs and sedan-type vehicles.

View full abstract

Drivers often encounter situations requiring immediate and faultless decision of subsewquent tactics. So, continuous observation of the surroundings for safety confirmation is needed during driving. In estimating driver sptitude, therefore competence for handling multiple sources of information and integrating the substantial amount of information according ot real drive should be considered. In this study, a development of a driving simulator evaluating driver's performance of cheching the mirrors, whose scenes and operations are suited to real car, were conducted. Through an experiment contrasting older adults and younger adalts, considerable declination of the performance among older adults was revealed by this driving simulator.

View full abstract

Recently, some studies about driver's sitting posture in a car have been pushed forward from the view points of fatigue reduction and easy driving. This study verified that one of the causes of driver's strain was muscle activities when the driver voluntarily kept his/her sitting posture from being disturbed by the external force while cornering. And it was suggested that it was possible to reduce the driver's strain by improvement of seat shape; it was improved using some physiological measurements(electromyogram, heart rate, respiration rate and blood pressure) and behavior observation with image analysis. Furthermore with results of sensory evaluation, it was suggested that supporting sitting posture contributed to easy steering and to embodiment of a car, that creates feeling of unity between the driver or passenger and the car.

View full abstract

The state-of-the-art in engine simulation or in simulation in general is constantly advancing. Simulation technologies have traditionally been segregated into specialties that simulate one sub-system while greatly simplifying the interaction to other components. This is acceptable in traditional design methodologies but became inadequate in the context of “integrated system”, which is currently emerging in industry. The development in the computer hardware had reached a mature stage that help realizing this integrated system approach. This paper presents a powerful methodology that can be used in modeling the integrated vehicle thermal partial systems in order to understand and quantify the thermal behavior of the vehicle sub-systems; especially during the engine warm-up. Having been able to model, the thermal system, the engine transient performance can be optimized with respect to the control parameters of these sub-systems.

View full abstract

The influence of rider action on motorcycle behavior is so significant that it is impossible to verify the simulation model by running data with a human driver. For the purpose of identifying the characteristics of a motorcycle which does not contain rider influences, we have developed a radio-controlled, unmanned motorcycle. The results of the actual running test show the effectiveness of the system for motorcycle analysis.

View full abstract

Remarkable advances have taken place in chassis control technology, such as antilock brake systems (ABS), vehicle stability control(VSC) systems and so on. In addidtion ,the Pre-crash safety system (PCS) in order to reduce collision damage had been introduced. This system judges the collision probability based on output data from the Millimeter-wave Radar and helps driver brake operation. This paper describes a new assist system that incorporate a dynamic control system with forward monitoring technology. This new system helps drivers steer operation during the emergency collision avoidance, which was developed based on analysis of driver behavior in accidents.

View full abstract

Aerodynamic properties of heavy-duty trucks are modified with wind tunnel tests and numerical simulations. Since the Reynolds number of trucks are very high, the Reynolds number of the wind tunnel tests with the small scale models is smaller than those of real trucks. In this paper, we discuss the effect on trubulence of the aerodynamics performance of the small scale models. The flow-fields of the small scale models with turbulence grid were similar to those of the large scale models. That is the practical Reynolds number of the wind tunnel test with turbulence grid was higher than geometric Reynolds number. This result indicated that turbulence grid was useful to estimate aerodynamics performance of large scale vehicles by using small scale models.

View full abstract

The relentless development of gasoline engine design for improved performance and fuel economy can exploit the benefits of a coutinuous variable valve timing and lift system. A new engine using a version of this system achieves both high performance and low fuel consumption without need for compromise.

View full abstract

The North America-specification SUV was the first car employed 3L V6 engine that meets California's Super Low Emission Vehicle(SULEV) standard without secondary Air. We found the effective technique for the HC trap system in process that we compared the HC trap system and the secondary air system. After that, we challenged to reduce HC more. One is to keep the time that injected fuel evaporates on cold start, the other is use of the intake flow control valve(IFCV). We show the possibility that liquid fuel combustion increased in case of using IFCV and we offered that the way to reduce that.

View full abstract

According to preliminary study on the cooling fan with particular shaped blades, it has been realized that its fan characteristics shows remarkable Reynolds number effects in case of the experiment, while it is not noteworthy in case of CFD. The differences in fan characteristic are consisted with the vortex structures near the fan. Hence, in this report, the differences are investigated to explain its mechanism using CFD and flow visualization technique. As a result, it is found that the tendency of axial flow pattern along with decrease in Reynolds number.

View full abstract

The “handware-in-the-loop simulator (HILS) method” was developed for measuring fuel economy and exhaust emissions of heavy-duty hybrid electric vehicles (HEVs). To establish the HILS method, the following actions were taken. (1)Typical HEV models for HILS system were proposed so they can be adapted to all types of heavy-duty HEVs that will be launched in the next several years in Japan. (2)Test procedures of HEV components such as engines, motor/generators, and batteries were proposed to measure parameters of HEV medels. (3)A procedure for varifying the HILS system was developed.

View full abstract

Driving through intersections still represents a hazardous task because they remain places where most angle-collision accidents usually occur. Therefore, to reduce these accidents, driver behavior upon entering a no-signal intersection was investigated. Vocal Information was provided to allow drivers to recognize this no-signal intersectin. By analyzing driver braking behavior, the appropriate timing of this information was determined. The effect was that drivers were able to initiate braking early enough to smoothly stop their vehicle before crossing no-signal intersections.

View full abstract