In the previous studies on the effect of fuel composition on super lean burn (combustion with an excess air ratio of 2 or more), it was found that the lean limit will be significantly expanded by changing the fuel composition even for hydrocarbon fuels that do not contain oxygen or nitrogen. In this report, we focus on the ignition delay time and laminar burning velocity of hydrocarbon fuels on the expansion of the lean limit based on the experimental results.

View full abstract

For the purpose of improving the performance of the centrifugal pendulum vibration absorber, we have focused on the generated torque andconducted theoretical analysis. In this study, the performance was evaluated by the transient dynamo test in order to clarify the vibration reductionperformance in the actual vehicle. We also constructed a multi-degree-of-freedom theoretical analysis model compatible with the testing machineand showed its validity by comparing it with the experiment.

View full abstract

This study deals with estimation method for lateral tire force characteristics of an actual road using longitudinal force to measure. Based on the braking force characteristic measurement on the actual road conducted in the previous research, a brush model is used to estimate the lateral force characteristic based on the obtained μ-s characteristic. Each brush on the brush model has an adhesion region and a sliding region, so from the relationship of static friction characteristics, and dynamic friction characteristics, this model is extended from the longitudinal force to lateral force. For this transform, the adhesion region and the sliding region are estimated based on the braking force characteristics identified by the magic formula, using a tangential equation for simple magic formula, these two regions are estimated, and an algorithm for lateral force characteristic estimation is constructed.

View full abstract

In this study, a 5-degree-of-freedom model, which consists of a 4-degree-of-freedom model plus a single frame degree of freedom, is analyzed using eigenvector equations. The mechanism by which the damping characteristics of the frame affect the stability of the wobble mode is investigated in detail. From the analysis, among the six types of frames, the twist flexibility of the front fork has a strong influence on the stabilization of the wobble mode. Especially, the influence of the frame twist angle within the front tire lateral force changes the phase of the front tire lateral force and stabilizes the wobble mode.

View full abstract

The straight running stability of motorcycle is greatly affected by frame flexibilities. In this study, six types of 5-degreeof- freedom models are used, in which a single frame flexibility is added to the basic 4-degree-of-freedom model. Changes in energy flow are calculated in order to analyze the effect of frame flexibility on weave mode. Specifically, a formulation based on the eigenvector equation is used. As a result, the weave mode can be suppressed by adding a damping ratio to the twist flexibility model of the rear swing arm.

View full abstract

A high-performance semi-active suspension utilizing electro rheological fluid (ERF) has been a promising technology to improve ride comfort for automobiles. ERF is a functional fluid that reversibly changes viscosity when electric field is applied.In this study, a non-hydrous ERF consisting of ion-doped-polyurethane (PU) particles and silicon oil was studied. Damping force of ER damper with the ERF was confirmed to be controllable by applying various voltage. However, the damping force was significantly reduced after heat load. The main factor for the performance degradation was presumed to be PU decomposition. To suppress the decomposition of PU, chemical structure of PU was studied. As a result, by improving the hardener composition, heat degradation of ER effect and ER damper was significantly reduced.

View full abstract

In order to improve wind noise in high frequency range above 2kHz, this paper proposes a new technique focusing on high damping glass-run to reduce glass transmission noise due to coincidence effect at low cost. The technique is characterized by controlling energy transmission by utilizing impedance matching between glass and glass-run without changing materials.

View full abstract

The wavelet cross-correlation analysis was used for the in-cylinder pressure and the engine outer surface vibration acceleration to investigate the time delay from the combustion impact to the vibration acceleration for each frequency component. The main results are as follows: Acceleration peaks were observed at 2500 Hz and 8000 Hz on the outer surface near the combustion chamber. This is because the pistonconnection rod coupled vibration occurs at 2500 Hz and the combustion chamber resonance at 8000 Hz. At 2500 Hz and 8000 Hz, there is a time delay on which a large correlation of 0.8 or higher appears between the in-cylinder pressure and acceleration. At 800 Hz, 2000 Hz, 3150 Hz, 6300 Hz, 8000 Hz, 10000 Hz, there is no significant time delay, and therefore the vibration reaches the engine outer surface from the combustion chamber via the liner and cylinder head with the shortest path. At 1000 Hz, 1250 Hz, 1600 Hz, 2500 Hz, 4000 Hz and 5000 Hz, there is a time delay of 10 to 30 deg. This time delay is probably due to the excitation of some structural vibrations, such as the piston-connecting rod coupled vibration.

View full abstract

Although CAE analysis is used to predict occupant head protection performance in the event of an impact in the interior in line with U.S. regulations, the time required for this analysis is an obstacle to shortening the development period. To help address this issue, a 1D model was developed and studies carried out into the application of MBD to occupant protection performance. As a result, the prediction accuracy of the HIC was found to be 98% compared with 3D-CAE. And the analysis time was reduced by 99.8% because the analysis didn't involve geometry.

View full abstract

This paper describes a methodology for robust design in crash analysis. We organized a series of robust design processes for crash analysis and showed that it is possible to classify/predict deformation patterns, judge whether they are good or not, identify contributing parameters by applying statistical/machine learning methods in each process. By using a prediction model as a surrogate model, we achieved an extensive search in the design space in a short time.

View full abstract

This study focused on pedal misapplication accidents which have become a social problem. A driving simulator was used to reproduce the situation in which missteps are likely to occur, which was extracted from Japan Traffic Accidents In-Depth Database. We analyzed the pedal operation when the vehicle was stopped and when it was restarted. The stepping method that inverts the ankle joint requires less movement than the stepping method that moves the entire leg, making it easier to step on the accelerator side when braking. In startled situations, pedal depression speed was shown to increase, which could lead to unintended acceleration.

View full abstract

In this study, an automated driving vehicle which is running on a highway starts the function of Minimum Risk Manoeuvre (MRM), and changes a lane from the second lane to the first lane. In this scenario, various conditions of lane change and deceleration were prepared, and driving behavior of the driver in the vehicle behind the automated driving vehicle was evaluated by using the driving simulator. And then, important items for safer lane changes were considered. For example, in case that the vehicle under MRM decelerates during a lane change, deceleration has to be less than 2 m/s². Also, in case that the vehicle under MRM starts deceleration after the completion of a lane change, a certain period more than 2 seconds for which hazard warning lamp is activated before start of deceleration is necessary.

View full abstract

Visible-light photocatalysts are promising materials for car cabins, as they exhibit multiple functions under indoor light conditions, including antimicrobial and antiviral activities. Owing to the increasing demands for fast-acting sanitary materials, we studied the antimicrobial activities of nitrogen-doped titanium oxide loaded with Cu (Cu/N-TiO₂), a visible-light photocatalyst, in short time reactions with Escherichia coli. The survival rate of E. coli on a Cu/N-TiO₂-coated surface rapidly declined to 0% after 60 min, as assessed using a newly developed assay system and three types of resins. The morphological changes observed in E. coli resulted from the production of radicals after light exposure.

View full abstract

We measured the internal residual stress of quenching induction hardened axle shaft by the contour method, and then constructed a simulation system for the bending correction process by considering the existing residual stress. With the constructed simulation system, we quantitatively evaluated the effects of various factors on the residual stress relaxation behavior during bending correction, and proposed a unified parameter that can predict the residual stress relaxation behavior. Finally, we experimentally validated the availability of proposed parameter for controlling the residual stress relaxation behavior induced by bending correction process of the quenching induction hardened axle shaft.

View full abstract

It is important to understand the CFRP fracture mechanism of high-pressure vessels. In this study, we used 3D solid elements that take into account the damage characteristics and stacking thickness of CFRP as a calculation model, and performed damage progression analysis that express the decrease in the rigidity of CFRP. The fracture mechanism of high-pressure vessel is discussed by comparing the linear FEM analysis with this method.

View full abstract

We are aiming to build a system which provides a route with minimum risk in order to reduce accidents of elderly drivers. For this purpose， it is necessary to estimate the risk level of unsignalized intersections where accidents are likely to occur. Therefore, for estimating the risk level， we propose a method to estimate the available viewing angle at intersections based on semantic segment distribution generated from a street view image. The performance of estimation is evaluated through experiments using street view images. As a result, we achieved an accuracy of more than 80% from a single image.

View full abstract

In automotive wiper systems, a phenomenon called overrun, which is deviation of an actual reversal position from a desired position and causes noise and wiper damage, should be reduced. In addition, for the electrification of automobiles, reduction of power consumption of component parts is required. In this paper, multi-objective optimization of wiper motion trajectories is proposed by using the response surface method that considers the overrun and motor current as objective functions. Optimal motion trajectories satisfying both requirements of small overrun and current are obtained, in which optimal solutions depend on the direction of wiper motion.

View full abstract

Miller cycle engine can reduce pump loss of low-load range; however, engine performance of high-load range gets worse due to the decrease of air. Variable valve actuation system or high-boosting system is used to compensate the decrease of air, but the system costs high. In this study, intake valve closure (IVC) timing was investigated by simulation and experiment on heavy-duty diesel engine with single-turbocharger and with single-cam-profile. As a result, IVC timing at Bottom Dead Center reduced excess air ratio of high-speed range and reduced pump loss of low-load range while maintaining the engine performance of high-load range．

View full abstract

We investigated the influence of main-bearing asperity contact on combustion-induced vibration of a diesel engine by simulation. Main findings are as follows: As the viscosity of engine oil is increased, the asperity-contact pressure for a main bearing decreases and thus both vibration-transmission efficiency and decay rate decrease. The contribution of vibration-transmission efficiency to the engine outer-surface vibration is bigger than that of decay rate and thus the engine outer-surface vibration becomes small. Both asperity-contact pressure and oil-film pressure become small if the partial contact to the main bearing by crank-shaft elastic deformation is reduced by properly changing the main-bearing angle. As in the case of an increase in the oil viscosity, both vibration transmission efficiency and decay rate become low, leading to a decrease in the engine outer-surface vibration.

View full abstract

Ignition delays were systematically measured under wide and various engine operating conditions, including engine speeds, intake gas temperatures, intake gas pressures, intake oxygen concentrations changed with EGR, fuel injection pressures, and coolant temperatures in a DI diesel engine. An empirical formula to predict the ignition delay based on the Arrhenius equation was obtained with a multiple regression analysis from the experimental results. Ignition delays can be predicted accurately with the final proposed equation, which has three parameters, including the fuel injection pressure as well as the in-cylinder gas temperature and the oxygen partial pressure at the start of fuel injection.

View full abstract

To understand the dependence of ignition delay on the cetane number under various super-charging and EGR conditions in diesel combustion, ignition delays were systematically measured in a 0.83 L single cylinder diesel engine. The investigations were conducted over a wide range of intake oxygen concentrations, intake gas temperatures, and intake pressures with various cetane numbers to develop an empirical formula for the ignition delay based on the Arrhenius equation. The final proposed equation can adequately predict ignition delays with three parameters: the cetane number as well as the in-cylinder gas temperature and the oxygen partial pressure at the start of the fuel injection.

View full abstract

The Livengood-Wu integral has been applied widely as the simplest but most practical model to predict knocking or end-gas autoignition. The scientific nature of this empirical model was investigated by one of the authors. The integral value of 1/τ can be considered accumulated heat, meaning that 1/τ can be a conservable and transportable quantity, and its local integral can predict local autoignition in a heterogeneous air-fuel mixture or a diesel spray. Also, a set of several equations was developed to reproduce the temperature-, pressure-, and equivalence ratio-dependences of ignition delay time for a gasoline surrogate fuel produced using a detailed reaction mechanism. In the present report, ignition delay time equations have been developed for normal hexadecane. The Livengood-Wu integral with the equations has been applied to predict HCCI produced using a detailed reaction mechanism. When a period after distinct cool-flame reaction to ignition in an in-cylinder ignition process is prolonged, ignition timing predicted using the Livengood-Wu integral is retarded away from that produced using the detailed reaction mechanism, because the latter half of the integral is done in a distinct negative temperature coefficient region. The ignition delay time equation can be modified to weaken the negative temperature coefficient region and decrease the retard of predicted timing.

View full abstract

This paper proposes a reduced soot formation model for gasoline surrogate fuel with 72 chemical species and 409 gas phase reactions. We examined comprehensively the soot formation and its temporal characteristics calculated by the reduced and detailed model. The nucleation rate of soot particle was reviewed using the experimental data by a shock tube. As a result, we obtained the reasonable reduced model that is almost in agreement with not only the experimental data but also the calculated one with detailed model. The proposed model, reduced GSF model, for gasoline surrogate fuel can be applied to the 3D-CFD calculation of soot formation in an engine cylinder.

View full abstract

Cooling loss reduction during combustion period could be an essential measure for further improvement in thermal efficiency of diesel engines. Direct measurement of local and instantaneous heat flux at various points of the in-cylinder surface will play an important role to reveal detailed mechanism of the cooling loss phenomena. However, there have been very limited number of studies with state-of-the-art engines. This paper reports the outline of a newly-developed thin-film-thermocouple type heat flux sensor, which can be fitted anywhere and is durable under very high in-cylinder pressure (up to 35MPa) aiming higher thermal efficiency, and achieved results by the sensor.

View full abstract

In this study, the characteristics of exhaust gas temperature rise for different EH install positions was evaluated by experiments. In addition, the effect of EH install positions on the NOx purification rate in WHTC-cold test cycle was evaluated by simulation. As a result, when heated with EH installed on the front of SCR, exhaust gas reached target temperature rapidly, and therefore higher NOx purification rate was obtained. Also, it was suggested that electricity supplied to EH until the exhaust gas reach target temperature can be compensated by the power recovered with braking regeneration by combining with high-efficient braking regenerative systems.

View full abstract

In recent years, emission regulations have become more stringent, and particulate matter (PM) emitted from gasoline engine vehicles is also subject to regulation. PM emitted from a gasoline engine is suppressed by a gasoline particulate filter (GPF). However, unlike diesel engines, exhaust from gasoline engines flows into the GPF under more stringent conditions. Therefore, in this study, we performed numerical calculations based on WLTC, taking into account fluctuations in exhaust gas from gasoline engines, and confirmed the behavior of PM deposition and regeneration. At that time, the numerical calculation model of the previous research was also improved. Furthermore, a catalyst was supported on the GPF, and the catalyst performance was evaluated. As a result, it was suggested that continuous regeneration would be possible by improving the performance of the catalyst.

View full abstract

Development of a highly accurate prediction method for LOC is being carried out through CAE and experimental verification. Since 3 piece type oil control ring significantly effects on LOC, in this paper, lubricating oil behavior around the 3 piece oil control ring was estimated. The calculation results of lubricating oil behavior were showed qualitative agreement with the experimental data at engine operating conditions. Thus efficacy of oil behavior prediction method was confirmed.

View full abstract

This paper proposes a new drive system for a large EV that achieves low cost, high power, and low power consumption by combining conventional motors and a simple gearbox. This system runs using one motor in the low-speed range and two motors in the high-speed range, and can switch between the two modes smoothly. Furthermore, in the two-motor mode, planetary gears are used as a differential device when driving under light loads in the high-speed range, and as a reduction device when driving under heavy loads in the low-speed range. This reduces the loss of each motor and expands the continuous operation range of the system. Bench tests showed that switching modes can increase the continuous operating range of the motor system by 36.2%, while enhancing its heat-resistance reliability.

View full abstract

Since the safety of automobiles depends on the friction characteristics of the road surface, it is very important to understand the friction characteristics between the tires and the road surface. However, there is almost no data on the road surface friction characteristics on actual roads. In the previous paper, it was proposed not only the basic design of the friction characteristic measurement system on the actual road surface but also a road friction estimation method. But the versatility and practical application of the estimation method have not been sufficiently studied. Therefore, in this research, we confirm the validity and versatility of the method for estimating the road surface friction characteristic indexes using the friction characteristic measurement system designed in the previous research.

View full abstract

Drivers' head movements are informative measures for evaluating the safety of elderly drivers. However, those measures are too technical for general elderly drivers to understand the meaning and how to improve them. This paper applied a principal component analysis (PCA) on elderly drivers' head movement measures driving a simulator, resulting in integrated head movement measures as principal axes that are easily interpretable: steadiness, quickness, and timeliness. Chart diagrams of PCA scores show an individual as well as group elderly drivers' characteristics. Based on the PCA scores, we discuss possible feedbacks for the elderly drivers.

View full abstract

We previously performed pedestrian collision detection using a deep learning method based on dashcam video data. However, the detection accuracy was poor owing to insufficient training data. Herein, we attempted to improve the accuracy of the detection for Advanced Automatic Crash Notification System (AACN) using data augmentation, which increases the amount of data by adding artificially generated training data. As a result of comparing the effects of multiple image processing methods on the detection rate, the detection rate increased to 86.85% by adding training data with reduced contrast. This rate was 34.37 points higher than the conventional rate.

View full abstract

Sixty-five elderly drivers participated in an experiment to develop a risk estimation test that can measure self-monitoring ability. The test consisted to point hazards, blind spots, signals and road sign by touching display in a Three-Dimensional Computer Graphics (3DCG) image from the driver's viewpoint on a 21-inch touch panel display. After the test, participants were asked to self-evaluate the rate of the total objects they could touch for safety, and to select a velocity for their next driving. The results were compared with those of non-elderly drivers. And the relationship with cognitive function measured by the TMT-B was also examined. In addition, the variables affecting velocity selection were analyzed. The results revealed the following points. The hazard pointing rate of elderly drivers was significantly lower than that of non-elderly drivers. There were many elderly drivers whose self-estimation of the hazard pointing rate was high, even though the actual rate was low. There was a significant correlation between the decline in cognitive function and the decline in the potential hazard like blind spots at intersections pointing rate. There was no relationship between cognitive function or self-estimation of hazard pointing rate and selection velocity.

View full abstract

Predicting traffic accidents is an important issue for improving public safety. In this study, we developed an AI model which predicts the probability of traffic accidents in Fukuoka City with spatial and temporal resolutions of ~130m and 1 month, respectively. A multimodal machine-learning model was developed by combining various structured data (roads, demographics and economic statistics, weather, events, etc.) and satellite imagery, and was trained using personal injury accident data between 2016 and 2017 in Fukuoka City. As a result, the model succeeded in predicting the outcome for Fukuoka City in 2018 at an AUC of the ROC curve of 77%.

View full abstract

In our previous studies, a bolt-nut connection with slight pitch difference was considered towards realizing anti-loosening performance and high fatigue strength through axisymmetric finite element method (FEM) and experiment. Also by applying three-dimensional FEM, the nut tightening/untightening process was analyzed to confirm anti-loosening performance indirectly. In this study, Junker's type loosening experiment based on DIN standard is used to confirm the anti-loosening performance directly. The results suggest that suitable pitch difference may provide good anti-loosening performance. The 3D FEM simulation is in good agreement with the experiment. The anti-loosening of the pitch difference nut is discussed by comparing the loosening of the normal nut.

View full abstract

The pitch difference nut can be used in automobiles and other industries to improve anti-loosening and fatigue strength with low cost. In this paper, based on the suitable pitch difference α experimentally obtained previously for JIS M12 and M16, the suitable pitch difference is discussed for other bolt nominal diameters. Here, the overlap thread length is calculated from the suitable α obtained for M12. Then, the same value of is assumed to estimate the suitable α for other diameters. The validity of this theory is confirmed through calculating the prevailing torque for other diameter by applying FEM analysis.

View full abstract

The reduction of accidents caused by elderly drivers is a priority subject to achieve safe traffic. Specifically, car to bike collision at crossing with bad visibility is one of common accident scenario. Cognitive decline is implied as a cause, but the mechanism is not elucidated yet. Therefore, this study aims on the visual behavior analysis of elderly drivers at intersections through driving simulator experiment. Additionally, several driving assistant systems are installed and improvement of visual cognition level is also evaluated. Consequently, distinctive visual features of elderly drivers are inferred; recognition time of elderly drivers are slower than experienced drivers and the time is improved with cognitive assistance. Further, suitable features of driving assistance for elderly drivers are demonstrated.

View full abstract

The purpose of this study is to construct the quantitative evaluation method of steering feel based on the sensitivity evaluation. In this study, we conducted experiments simulating and evaluating steering reaction torque characteristics in the off-center range by a driving simulator. We performed principal component analysis of sensitivity evaluation values and analyzed correlations with physiological indices. The results showed the strong correlation between electrocardiogram LF/HF and LF/(LF+HF), which are sympathetic nerve activity index, and comfort, which shows the possibilities of more concentrated driving with favorite reaction torque characteristic.

View full abstract

In order to improve the cooling performance of a vehicle, we carried out computational fluid dynamics (CFD) optimization of the front-end cooling structure. To improve the efficiency of optimization calculation, we introduced a method using variable fidelity CFD models and proper orthogonal decomposition (POD). Firstly, in this method, the POD modes are calculated from Pareto solutions of low-fidelity CFD optimization. Secondly, an optimization calculation is performed using high-fidelity CFD models with only the dominant POD modes. As a result, we obtained solutions showing performance values equal to those of the previous method at 50% of the computational cost of it.

View full abstract

WLTP permits to test 2WD vehicles with a 4WD chassis dynamometer. Therefore, in this study, the control methods of 4WD chassis dynamometer were evaluated in the non-powered wheel speed following control mode (2WD operation) and the front and rear wheel speed synchronization control mode (4WD operation). We examined the impact of the difference in the 4WD chassis dynamometer control methods on fuel consumption and exhaust gas emission, using a diesel vehicle and a hybrid vehicle on the 4WD chassis dynamometer. For the exhaust gas emission and fuel consumption, a good correlation was confirmed even with the different control methods of 4WD chassis dynamometer.

View full abstract

Thermal Interface Material (Gap filler) is used to transfer the heat of the battery to the cooler in the EV battery pack. Since it is used without applying surface pressure, it is need to understand the interfacial thermal resistance between the adherend surfaces. In this study, we established a thermal resistance evaluation method that can predict durability characteristics at the test specimen level with few device restrictions

View full abstract

In relation to weight reduction in automobile, it is attracting attention of various welding methods for resin in infrared welding. The adherends are heated by non-contact infrared rays, and the welding interface are melted and jointed. In infrared vibration welding, the adhereneds are melted by irradiating with infrared rays and jointed by the frictional heat generated by the contact vibration of them. This paper reports the differences in the mechanical properties and structure of the welding interface area of PPS resin made by these methods.

View full abstract