To correspond with CO2 reduction from the automobile, in conjunction with electrification, improving the thermal efficiency of ICE is crucial and lean and EGR diluted combustion are being studied. It is important to enhance combustion in lean and EGR diluted condition and it is known that the effects of fuel components are significant. In this study the effects of fuel components on the lean & EGR diluted combustion are examined with L4 engine and the fuel specifications required to enhance lean combustion are reported.

View full abstract

To reduce pollution and improve thermal efficiency, the characteristics of combustion in internal combustion engines have been investigated for many decades. For different concerns and challenges, research on turbulent combustion was conducted using a constant volume vessel by adding many alternative dilutions. According to previous researches, several essential parameters are discussed that govern combustion performance like Lewis number, Karlovitz number, and so on. However, the mixtures used in these experiments were based on the ratio of 1:3.76 between O₂ and N₂. In this research, the authors focus on the influence of different additions on the combustion performance, which bases on the free ratio between O₂ and N₂, to see whether the parameters still govern the process of combustion or not. By the results of this research, it was found that the combustion performance changes greatly and the governing parameters also shift when the N₂ ratio reduces.

View full abstract

The objective of this study is to clarify the effect of deformation of elements on winding radial displacement. Strain gauges were attached to specific elements to measure the deformation of the elements in width direction. The axial displacement of the sheave was also measured by displacement sensors. The winding radial displacement of belt was calculated referring to displacement of the sheave and deformation of the element. It was found that the influence of deformation of element in width direction was not negligible, while the radial displacement was principally attributed by the tilt of the movable sheave as previous studies mentioned.

View full abstract

Wireless power transfer (WPT) to in-motion electric vehicles can extend the cruising range without additional batteries. Our group has already proposed a novel dynamic WPT system using in-tire and in-wheel repeater coil, which can shorten the air gap between the coils on the road and tire sides. In WPT system, the air gap should be as small as possible from the viewpoint of efficiency and leakage electromagnetic field. However, it is necessary to have a sufficient air gap to avoid coil damage by tire deformation. The maximum tire deformation when overcoming bumps of various heights at different vehicle speeds is experimentally measured with two different tires, normal tire and self supporting runflat (SSR) tire. The measured results show advantages of using SSR tire for the proposed WPT system.

View full abstract

We executed real road test reproduction with Battery Electric Vehicle (BEV), a key technology for electrification of powertrains. In the method we formerly studied, it was difficult to generate the same dynamometer force with the road test whilst altering the vehicle condition, such as State of Charge (SOC) and driving mode, against the road test. By converting the measured road load into a gradient force coupled with Road Load Simulation (RLS) dynamometer control, it becomes possible to generate the equivalent road load regardless of the vehicle condition.

View full abstract

Wireless power transfer has been proposed to solve the issue of the electric contact fault or maintenance in the direct charging system. In this research, a dynamic wireless power transfer system is developed for auto guided vehicles. Not only the transmitting performance but also the durability of the transmitter coil is simulated and evaluated with the actual measurement. Then 1.8kW DWPT is achieved with the transmitter coils that have enough durability for loading auto guided vehicles. This research also introduces the embedment of the power transmission system in the road surface of the wireless power transfer system and the change of the transmitter coil with time and settings. It is revealed that there is change in the coil parameters by setting, but no changes after 10 months in an outdoor situation.

View full abstract

This paper proposes the new concept of preview controller for active vehicle suspension. This preview controller generates an unsprung mass state value map using data obtained from a positioning system, accelerometer, and the like. It then realizes control using the generated map and positioning system. The accuracy of unsprung mass displacement estimation and the advantage compared to feed-back control and preview control with data processed online were validated in equations, simulations, bench tests, and on-road tests.

View full abstract

It is necessary to consider the coupling between the power train system and suspension system for the unsprung mass vibration that occurs when the vehicle starts. In this study, we constructed a dynamic model that takes into account the stiffness and inertia of the power train system in the suspension and tire models, and confirmed that the model reproduces the actual vibration phenomenon. Furthermore, we clarified the conditions for instability based on the relationship between the suspension vertical resonance and the power train system resonance.

View full abstract

This study proposes a technique to reduce vehicle longitudinal vibration at surface input without worsening the shock feeling at projection rideover by combining a suspension model with elastic principal axes and a tire longitudinal force model even when the suspension longitudinal rigidity is low. Furthermore, by considering the coupling with the suspension member and the differential gear, and by using the actual tire input characteristics measured in the drum projection test, it is shown that it is possible to reduce vehicle longitudinal vibration at projection ride-over. The intended effects of the numerical simulation were also confirmed by actual driving tests.

View full abstract

In this study, application of noise map for the prediction and examination of road traffic noise are discussed for Higashiosaka City. Noise mapping is performed based on the 2015 road traffic census data of Ministry of Land, Infrastructure, Transport and Tourism (MLIT) by employing ASJ RTN-Model 2018, which is a model developed by the Acoustical Society of Japan (ASJ) for predicting the road traffic noise (RTN). The population exposure is estimated based on the national base map of MLIT and the 2015 population census data of Ministry of Internal Affairs and Communications. The noise level and population exposure are examined for several hypothetical cases, such as reduction of vehicle noise, adoption of porous asphalt pavement.

View full abstract

The purpose of the present study was to examine the relationship between the severity of thoracic fracture injuries sustained by vehicle occupants in traffic accidents and their bone mineral density value. Calcaneal ultrasonic speed of sound (SOS) was measured in 71 patients injured in a traffic accidents that occurred between June 2016 and September 2019. The SOS value decreased with age, for both males and females, although males had higher SOS values than females. An analysis of the relationship between SOS value and injury severity of rib fractures indicated a significant difference in the mean SOS value between those in the Abbreviated Injury Scale (AIS) 3+ fracture injury group and those in the non-fracture group. Using Receiver Operating Characteristic (ROC) analysis techniques to estimate the threshold for thoracic fracture injury, SOS 1550 [m/s] was found to be the boundary between the high and low fracture risk groups. This value corresponded to the SOS of early 50 years old males and late 40 years old females.

View full abstract

We developed a multi-shift stereo camera and a monocular vision detection (MSMVD) employing top view image subtraction method. Far object detection performance can be preserved while obtaining a wider FOV without the use of an expensive image sensor. We also propose two methods in velocity estimation for MSMVD. One is using single ranging result and view angle. Another is a combination method with Kalman filter. We confirmed the improvements in accuracy and responsiveness of estimated velocity and found that the collision judgement in the case of crossing bicycles within only 3 frames which is approximately half of the conventional method.

View full abstract

A minimal risk maneuver (MRM) stops a vehicle in a case when the driver does not respond to the request to intervene (RTI) delivered from the system of Level 3 or lower driving automation or in a case when Level 4 automated driving vehicle will go out of the operational design domain (ODD). This manuscript classifies the triggering conditions of MRM and the corresponding appropriate MRM.

View full abstract

A human predictive characteristic may affect the traffic accident factors such as prediction failure and carelessness to other movements. In this paper, we propose a new approach to simulate how human vision predicts the driving environment during driving, and to clarify cognitive mechanisms, using deep neural networks that incorporate predictive coding, which is one of the leading theories as the operating principle of the cerebral cortex. Predictive coding assumes that the brain’s internal models predict the visual world at all times and that errors between the prediction and the actual sensory input further refine the internal models.

View full abstract

In this paper, in order to clarify the relationship between human prediction characteristics based on prediction coding theory and traffic near miss incidents, analysis for the front video of drive recorders recorded traffic near miss incidents was conducted using deep learning model which simulates human vision, and two hypotheses were proposed. Using the prediction error indicator based on the hypothesis, it was confirmed that 30 out of 60 near miss video can explained by the hypothesis. It was indicated that the change of the prediction error effects the attention of the unconscious and may lead the traffic near miss incidents.

View full abstract

Many studies on driving behaviour and human characteristics often use multiple questionnaires, that is burdensome for older drivers. It works efficiently if only valid items are used to adequately represent differences among older drivers. The aim of the present report is to develop an exhaustive questionnaire incorporating several driving-related scales. The analysis was conducted using the latent rank theory. As a result, the 121 items of the existing questionnaire could be reduced to 45 items without significant loss of information. With the new questionnaire, it is possible to measure 8 different subjective assessments, such as safe driving orientation and awareness of change.

View full abstract

This study examined the effects of the servo press's motion control and lubrication on the shape-freezing properties of hatshaped product of ultra-high strength steel formed by draw forming. Bending motion is effective in decreasing camber angle in shape freezing but is not effective in spring-back. Lubrication is effective in reducing camber angle in shape freezing but deteriorates shape freezing against spring-back. Shape freezing in draw forming of hat-shaped parts is affected by two factors: warpage due to unbending of the vertical wall and spring-back in bending on both sides of the web surface. In the case of the inching motion, friction between the die and the steel plate is suppressed, and the load during bending and unbending is reduced. When lubricant is used, friction is reduced due to the presence of an oil film between the work piece and the die. Therefore, warpage of the vertical wall is suppressed by the inching motion and lubrication. When bending is performed while tensile force is applied, spring-back decreases. The reason for the increase in spring-back due to lubrication is that the tensile force at the R shoulder of the die is reduced due to friction, and the effect of the tensile load on the bending of the R shoulder of the punch is reduced. The effects of press motion and lubrication on shape freezing were clarified by estimating the amount of strain that a steel plate undergoes during processing by measuring the half-value widths of the vertical wall and bending area from X-ray diffraction experiments.

View full abstract

Aluminum electrolytic capacitors are used widely for automotive electrical equipment. However, it is complicated to evaluate the lifetime for the actual operation condition varying ambient temperature and ripple current, due to the temperature dependence of the impedance and lifetime acceleration factor of aluminum electrolyte capacitors. In this paper, we propose the residual-lifetime calculation by the Electrical and Thermal Multi-Domain model (VHDL-AMS) and show the lifetime calculation results of the booster capacitor in the fuel injection system.

View full abstract

In order to develop a Transformer-based spoken dialogue system for natural dialogue about the scenery like a passenger, we collected a dataset of dialogue between role of drivers and passengers who engaged in a dialogue by sharing scenery driving movies by online. The collected dataset was analyzed to determine the extent to which utterances that talked about scenery or involved self-disclosure occur. The results showed that basic chit-chat performance was most important, even for chit-chat dialogues that talks about scenery.

View full abstract

In-vehicle electrical equipment is becoming smaller and more sophisticated. For the thermal design of these devices, it is important to consider not only the semiconductors, which are the main heat source, but also the passive components (resistors, capacitors, etc.) used in the peripheral circuits. In this paper, we propose a passive component model compatible with VHDL-AMS, which has been widely used for multi-domain analysis of circuits and heat. We explain the issues and the taken measures in modeling chip components, and discuss the analysis results using the model.

View full abstract

This study was conducted to select appropriate evaluation words for sound quality evaluation of car audio systems and to clarify the required sound quality. From the 997 adjectives prepared, 104 were selected as appropriate evaluation words through an Internet survey. Next, a listening experiment was conducted to select words with no overlap in meaning, and the evaluation results were classified by cluster analysis and refined by graphical modeling. As a result, 11 evaluation words were selected, including a preference word. Then, the results of causal analysis using covariance structure analysis showed that ‘Ear friendly’ had the greatest influence on the evaluation word ‘Like,’ followed by ‘Natural’ and ‘Sense of spread.’ This indicates that the sound quality of car audio desired by many people is ‘a natural sound with little stimulation.’

View full abstract

The characteristics of a 4WD vehicle in a high-speed straight driving range were analyzed against a 2WD vehicle. A characteristic of 4WD vehicles is that they have differential gears on the front and rear wheels, so the two differential gears increase yaw damping. As a result, the gain during steering is reduced, the phase delay is reduced, and the effect of suppressing disturbances such as crosswinds is increased. These are probably the reasons why 4WD vehicles are said to have a better feeling of going straight at high speeds than 2WD vehicles.

View full abstract

The effects of the oxygen content in fuels on the combustion characteristics and exhaust gas emissions were investigated in a diesel engine. The oxygen contents were widely varied with the blend ratio of diglyme, dimethyl carbonate, and diesel fuel, maintaining similar ignitabilities. With increasing oxygen contents, the degree of constant volume heat release increased with reduction in afterburning, resulting in higher indicated thermal efficiencies. However, the indicated thermal efficiency showed a maximum at around 27 mass% of the oxygen content in fuel and further increases in the oxygen contents resulted in lower indicated thermal efficiencies due to larger cooling losses.

View full abstract

Improving the thermal efficiency of internal combustion engines is essential for reducing CO2 in the transportation sector. In the previous report, we found that hydrocarbons with lower molecular weight extend the lean limit of the super lean-burn condition. In this report, in order to investigate the relationship between molecular weight and lean limit, we conducted some engine tests and detailed reaction calculations with hydrocarbons with high molecular weight. We also studied about the effect on the lean limit when using the feedstock materials in petroleum refinery with various molecular weight.

View full abstract

The spray combustion characteristics of OME3 were investigated using numerical simulation. Spray observation was made in a constant volume vessel and numerical simulations are validated via the experimental data. The calculation results give good agreement with the experiments. The results show that equivalence ratios inside OME3 spray are smaller than diesel fuel because the stoichiometric air/fuel ratio is small. OME3 spray has a wider high temperature region, and CO and NO are formed earlier compared with diesel fuel. Higher concentration of CH2O is formed near the center of OME3 spray, which suggests the low temperature oxidation proceeds inside the spray.

View full abstract

A high-accuracy knocking prediction model with low computational loads is necessary to develop thermal-efficiency improvement technologies for SI engines efficiently using computational techniques. Livengood-Wu integral has been applied widely as the simplest model for predicting knocking. In the previous reports, ignition delay time equations for a premium-gasoline surrogate fuel were developed to reproduce the temperature-, pressure-, equivalence ratio-, and EGR-dependences of ignition delay time produced using a detailed reaction mechanism. “Reverse Livengood-Wu integral” using an error correction equation was proposed to cancel the advances of timing predicted using Livengood-Wu integral with the ignition delay time equations, from ignition timing produced using the detailed reaction mechanism. The reverse Livengood-Wu integral requires iterative calculation to seek the correct ignition timing. In the present report, it has been found that ignition delay times using the equations are shorter than those using the detailed reaction mechanism with the high initial pressures over 6 MPa. Therefore, the ignition delay time equations have been revised for the expansion of those application conditions to 12 MPa. Also, a new equation has been developed to correct the prediction errors without iterative calculation. It has been investigated whether autoignition prediction using these equations can be effective or not in predicting experimental knocking occurrence timings in an SI engine. The difference of several % in estimating unburned-zone temperature causes the difference of several crank angle degrees in predicting autoignition timing.

View full abstract

This paper reports the development factors for applying the in-cylinder direct fuel injection technology to the supercharged gasoline engine for motorcycle aiming at further improvement of fuel consumption, higher power and lower emission. In particular, since the bore stroke of the highrevolution motorcycle engine is smaller than that of the passenger car engine, the fuel injected into the cylinder tends to impinge on the cylinder walls and cause combustion failure and soot. Techniques for solving these problems are mainly reported.

View full abstract

In a direct injection spark ignition engine, strict control of pollutant emissions at cold start is required to comply with new regulations. Fuel temperature and wall temperature are especially important parameters because they are closely related to the fuel film formed by spray impingement on the wall. The purpose of this study is to clarify the mixture and fuel film formation process with wall impingement spray under low temperature fuel and wall conditions. Construction of a spray experiment equipment that can simultaneously cool fuel temperature and wall temperature, and Total internal reflection laser induced fluorescence (TIR-LIF) method was applied to the fuel film formed by wall impingement spray. TIR-LIF method can measure fuel film thickness by fluorescence from fuel film during the spray injection without the influence of the spray droplet. In this paper, the fuel and wall temperatures were controlled from 293 K to 253 K to investigated film formation process during spray injection. In addition heat of evaporation considering heat capacity of fuel film was estimated.

View full abstract

Oxymethylene dimethyl ether (OME) produced from renewable energy is a promising fuel for reducing Well-to-Wheel CO2 emissions and other pollutants. Especially the Soot-NOx trade-off of diesel engines is dramatically improved by using OME. Recent investigations revealed that the chemical structure of OME without C-C bond reduced soot production. In the present paper, we examined the use of OME3-5 in a single-cylinder diesel engine and proved improved combustion and emission characteristics. Simulation results indicate that the lower flame temperature and lower equivalence ratio due to higher oxygen content realized improved Soot-NOx trade-off.

View full abstract

In this study, we focused on comfortability in cabin and investigated an influence of vehicle interior design and sound on the total comfortability using VR system. In the test, various interior design and interior sound were presented in the VR system and the total comfortability was assessed in the subjective evaluation test. As the result, color of interior design and loudness and roughness of interior sound were found to have significant influence on the comfortability. In addition, synergetic effect between design and sound on the comfortability was observed.

View full abstract

A return map method for identifying chaotic behavior due to bouncing-ball dynamics in a drivetrain torsional system is described. In this paper, the method is applied to the unstable vibration behavior caused by the dynamic backlash characteristics of a dual mass flywheel (DMF) to confirm the detected chaotic behavior can be classified as a bouncing-ball system and to show the effectiveness of the method. Both 1D simulation and real vehicle experimental data are used as validation data.

View full abstract

This paper describes a basic discussion on a technique for the design requirement of body frame which can be applied for reducing the noise level by suppressing energy propagation of frame to panel. Instantaneous structural intensity was analyzed to visualize the energy propagation path of entire structure. “Impedance evaluation model” which enables to quantify the energy propagation at its centroidal axis was developed. By verifying the change of transfer impedance when stiffness ratio was set as a parameter, the panel vibration reduction was suggested to be possible if energy propagation path is controlled.

View full abstract

Operational Transfer Path Analysis (OTPA) was successfully applied to noise source contribution analysis especially for diesel engine mechanical noise. At first, as a reference, the crank bearing vibration was divided into the mechanical component and the combustion one which are induced from crank impact and cylinder pressure individually, and then OTPA was applied for detailed separation of mechanical noise out of overall engine noise. The OPTA result was validated by time-consuming experiments with reduced piston system inertia and smaller gear rattle excitation. The validation result showed the good accuracy of OPTA, which indicates its effectiveness to study engine noise reduction.

View full abstract

An injury severity prediction algorithm for AACN was developed using a logistic regression model to predict the probability of sustaining an Injury Severity Score (ISS) 15+ injury. National Automotive Sampling System Crashworthiness Data System (NASS-CDS: 1999-2015) and model year 2000 or later were filtered for new case selection criteria, based on vehicle body type, to match SUBARU vehicle category. Moreover, presence of the right-front passenger and its interaction with crash direction were considered, which affected risk prediction significantly especially in the side-impact crashes. Variable selection techniques were used to construct the final ISP algorithm with relevant features. In this paper, we presented results of injury prediction algorithms, which do consider the effect of a right-front passenger were proposed. The area under the receiver operator characteristic curve (AUCs) was used as the metric to evaluate model performances, AUC was 0.862 with the model for cross-validation. Delta-V, seat belt use, and crash direction were important predictors of serious injury, and moreover, the presence of right-front passenger was a significant injury risk modifier, especially for side impact crashes.

View full abstract

We proposed and validated a method for quantifying drivers' attentional resources while car driving. We also analyzed the relationship between driver's attentional resources and risk avoidance capability. We used a camera monitoring system (CMS) as an example of an indirect vision device and conducted subject experiments using a driving simulator. The results showed that there is a correlation between the driver's attentional resources and risk avoidance capability. We also verified the effectiveness of supporting driver's visual search by superimposing see-through virtual pillars on the rearward image and confirmed that the see-through pillars can reduce the driver's risk of collision.

View full abstract

Plastic flow joining of carbon steel and aluminum alloy was conducted, and joint strength was evaluated by fracture analysis and visualization of material flow to improve joint strength. The pushing load for maximum joint strength is 25kN, and the maximum joint strength was 6.4kN. Filling increased with increasing pushing load. The ring material reached the top of the groove and filled the most when pushed in with a load of 25kN. A prediction equation for joint strength was proposed based on fracture analysis. The predicted joint strength agreed well with the measured values. The flow of material was visualized by two-dimensional mapping of the hardness distribution near the joint. The material is filled into the groove by sliding deformation in the 45-degree direction. Based on the visualized material flow, a method was devised to enhance the filling of the lower groove and improve the joint strength by modifying the groove and jig geometry. However, the joint strength did not increase under the present conditions.

View full abstract

The percentage of people killed or seriously injured in traffic accidents is the highest at night, and about 40% of accidents occur at intersections. In this study, we propose a system for alerting drivers at intersections. The system uses the infrared camera and on-board distance measurement sensor in an infrastructure-type monitoring system. We mapped pixel coordinates obtained from both the infrared camera and on-board distance measurement sensor to obtain the location of the object type. After determining the dangerous scene, the driver can find a warning light that is fixed on the crosswalk and pay attention to the path road.

View full abstract