The purpose of this study is to improve the thermal efficiency of diesel engine by EGR gas dissolved fuel. The fuel improves spray atomization by EGR gas effervescent. Use of EGR gas dissolved fuel can be expected to reduce wall heat loss and PM emissions due to lean combustion. In addition, the reduction of NOx is expected by spray internal EGR effect using gas dissolved fuel. In this report, CO2 gas is dissolved in n-tridecane, the CO2 gas dissolved fuel is evaluated the effects on combustion characteristics and emissions compared with the conventional external EGR using diesel engine.
Toyota creates new methodology of powertrain system development using modeling to allow front loading. In this paper, the new methodology and the way of thinking, from a system development to a vehicle development phase by progressing with modeling, are presented.
Cylinder pressure of diesel engines are getting higher, and engine bearings are required to have improved fatigue resistance. Recently, to change to lead-free bearing, bearings with three layer, which are bismuth overlay and copper alloy lining on the back steel, started to be applied. To improve the fatigue resistance of bismuth overlay, the overlay is reinforced by alloying with Sb. The fatigue resistance is superior to conventional material. In order to improve the fatigue resistance of lining, solid solution strengthening components of Cu such as Sn, Ni are selected as the additive components. Developed lining shows 45% higher fatigue strength compared with conventional lining.
Engine bearings are used in high unit load and thinner oil film thickness, and seizure of the engine bearings by the contamination is concerned. Seizure resistance is confirmed by using the rig test which can simulate the seizure by scratches. Detailed observation results, polymer coating disappear at the ridge of scratch, and the lining material is exposed. The seizure of engine bearings occurs near the scratch, and the exposed lining material exists at this position. It was found that the coating material to which barium sulfate was added covered the lining mostly, and substances derived from engine oil were also attached. As a result, seizure resistance against contamination was improved. Durability tests of the coating material containing barium sulfate are performed and it is confirmed that there was no problem overall.
We have been using engine models for engine system development. Almost all engine testbed calibrations can be simulated through detailed modeling of air path and combustion and tuning of specific parameters. A practical application of engine model in development process, methodologies of engine modeling and accuracies of model based calibrations will be reported.
The characteristics of diesel fuel spray are very important for diesel ignition and combustion process affecting significantly on engine performance and exhaust emissions. In this study, using the constant volume vessel, which can simulate the gas temperature and pressure at the time of the fuel injection in the direct injection diesel engine, and a high-speed video camera, the observations of diesel fuel spray and combustion process have been made. In the experiments, the injection system having a direct-acting piezo-actuator was used to get arbitrary injection rate profiles which cannot be realized with conventional injection system. This paper reports the effects of fuel injection rate on the diesel combustion. Especially, the study focused on the inversed-delta injection rate.
Fuel efficiency of vehicle can be improved by reducing the drag torque when the A/T clutch is disengaged． To increase the distance between the plates can reduce the drag torque, but the plate distance is a complicated phenomenon that depend on the relationship of the oil flow between multiple plates． Due to its complexity, there are few cases of studying the distance between plates． In this report, we study the fluctuation of the plate distance and drag torque, due to the pressure between the plates, and create a mathematical model of this phenomenon．
A continuously variable transmission (CVT) is one of the automotive transmissions that transmits torque by the frictional force between the belt and the pulley. CVT fluid (CVTF) is designed to control the frictional force under the boundary lubrication. In this study, the mechanical properties of the tribo-film derived from the CVTF were investigated by nanoindentation technique. In addition, surface analysis methods such as TOF-SIMS, FIB-SEM-EDX, and AFM were used to elucidate the chemical composition and microstructure of the tribo-film. The relationship between mechanical properties and frictional behavior was discussed based on the surface analysis
This paper proposes a slip detection method for inverters of a BEV (Battery Electric Vehicle), which drives a vehicle by one traction motor with a differential gear and driveshafts. It is observed that the sign (positive/negative) of motor rotation jerk differs when tire slip happens. Based on this phenomenon, the proposed slip detection method determines the start of tire slip when motor rotation jerk of a while after oscillation occurs is positive values dominantly. According to vehicle dynamics simulation, it is verified that the method can detect slip start after actual slip occurs earlier than the former slip detection method.
This paper proposes and verifies the effectiveness of a method of maintaining driver arousal during conditional autonomous driving, focusing on the stimulation of pleasant emotions and preventing habituation. This method, which uses nostalgic music and seat vibration to change the stimulus applied to the driver in accordance with the extent of driver drowsiness, was found to comfortably maintain driver arousal over long periods of time.
The purpose is to provide comfortable driving by reducing driver’s physical fatigue. Warm and cool contrast bath therapy is used in sports to recover from physical fatigue. Similarly, we propose a method to blow warm and cool air alternatively from driver’s seat. We generated physical fatigue by continuous driving for 90 minutes. Subjective fatigue scale, skin blood flow and muscular stiffness is measured during the experiment (n = 7). We confirmed the proposed method reduced subjective fatigue scale and muscular stiffness, increased skin blood flow. This indicates the proposed method is effective in reducing driver’s physical fatigue.
This study focuses on the high-risk scene for bicyclist accidents wherein vehicle drivers pass through intersections. In particular, this study focuses on the situations where a Bicycle potentially crosses. Drivers who have different driving skill resulting from different age groups, including young-aged, middle-aged, and senior drivers, in addition to expert drivers were examined on the test course. The driving indices of potential collision risk to a bicyclist suddenly crosses were examined. Based on our analyses, we clarified that expert drivers operated the vehicle at lower speeds than young and senior drivers. Furthermore, it is necessary to support the pedal operation in addition to speed limit in specific driving situations depending on driving skill.
Drivers does not always make sufficient deceleration for accident prevention when they pass through potentially danger situation, such as a road with blind spot where a pedestrian may rush into the road. In this study, we set up a system that assists a driver with visual information for appropriate driving speed adjustment through potentially danger situation, and evaluated its effect through a test track experiment using an augmented reality vehicle.
In recent years, autonomous driving has been actively studied, but it is difficult to deal with irregular situations such as accident and construction sites. In such situations, remote driving technology is expected to serve as a backup for autnomous driving systems. Most remote driving relies on camera images as a major source of visual information. Therefore, it is important to investigate which characteristics of visual information (e.g., frame rate and image resolution) affect performance. In this paper, we conducted remote driving experiments of a real-scale automobile under various visual quality settings and investigated the effect on remote driving behavior.
In the evaluation of car aerodynamics, Computational Fluid Dynamics (CFD) are frequently used as well as a wind-tunnel. However, the CFD simulations consume a lot of cost and time. In this study, a surrogate model using the machine learning was developed to reduce cost and time of CFD. In the proposed model, the relation between car shapes and CFD results was learned for rapid prediction of pressure, velocity and coefficient of drag for aerodynamics. In this paper, we introduce the proposed model, the training dataset, the accuracy and the computational time.
We have developed a machine learning model to detect welding failure states, using only signals from acceleration sensors attached to welding robots for assembling automobile bodies at automotive factories. By applying acceleration data obtained from such robots over a period of roughly one year, the proposed model for multiple mixed classifications generated over 1000 feature quantities, allowing it to classify three welding states: “normal”, “welding tip disengaged”, and “welding anomaly”.
Automated vehicles must not cause any traffic accident which is reasonably foreseeable and preventable. It is important to detect the information around the vehicle precisely to achieve that safety requirement. In this study, quantitative evaluation method regarding detection accuracy about legal speed limits, other vehicles, and lanes is discussed and trial had conducted with several vehicles.
This paper proposes a real-time trajectory planning method for autonomous driving in urban areas. The following three conditions are key requirements to enable autonomous driving in urban areas. (1) Safety must be ensured with regard to the environment surrounding an autonomous vehicle. (2) Vehicle behavior must be smooth movements. (3) Implementation must be possible in real time. To achieve these requirements at the same time, we focus dynamic programming. This enables to plan a vehicle trajectory combining short-range sensor data and long-range high-definition maps with little computational load.
In order to improve thermal efficiency of gasoline engines, effect on lean limit by design parameters which are air-motion, ignition energy, high fuel pressure and multiple injection of DI injector were investigated. In this report, the combination of these parameters can achieve lambda 2.01 and reduce engine-out NOx to 0.44g/kWh. Furthermore, CFD helped us to understand which factors affect the improvement of lean limit.
To investigate the behavior of injected fuel during cold start of gasoline engines, a non-combustive method using exhaust gas without combustion was constructed. The THC concentration of exhaust gas is relevant to the quantity of fuel introduced into the cylinder at the current and next cycle. The sensitivities of the concentration to the amount of injected fuel, fuel property and intake port temperature were proved by the experimental data. The proved data were used to model THC behavior applying machine learning. The model was demonstrated high accuracy and applied to derive the injection strategy to achieve low THC emission.
Gasoline engines have a few too-quick combustion per a hundred cycles preventing advanced ignition timings, which eventually constraints the fuel efficiency of gasoline engine. To improve this situation, we investigated the cause of combustion variation in cycles through two experimental analyses. One is the analysis on the initial flame propagation by visualizing the inside of cylinder with a bore scope, and another analysis is on the effect from fuel and EGR gas concentrations around the ignition plug during initial flame propagation. These experimental analyses revealed that flame propagation significantly differs by each cycle, and the concentration of fuel and EGR gas do not effect on the initial flame development.
Our turbulent combustion model had provided turbulence distributions in a cylinder using random digits, and it was able to simulate combustion cycle-by-cycle variations in gasoline engines. However, fluctuations of the EGR ratio and the internal EGR distribution were not able to be calculated. So a multi-zone combustion model has been developed to deal with them. This calculation model makes us know how the fuel distribution in a cylinder effects the cycle-by-cycle variations. From this calculation results, it can be understood that the fluctuations of the EGR ratio and the internal EGR distribution do not have significant effect on the cycle-by-cycle variations. Some calculation results and the details of the multi-zone combustion model are shown here.
This paper reports the atomization process of fuel spray in gasoline intake port injection. The classification of the jet configuration using dimensionless numbers in fluid dynamics was estimated that the fuel spray in the port fuel injection condition is in the wavy region. A shadow graph photography was used to visualize the liquid sheet breakup process. It was confirmed that the fuel injected from the nozzle formed a liquid sheet. For the subsequent breakup, it was found that the liquid sheet broke up into droplets with a distribution along the axial distance of the nozzle, and the secondary breakup, in which the droplets broke up into smaller droplets, rarely occurred.
In this paper, the dynamic characteristics of fuel spray droplet of multi-hole nozzle for port fuel injection were investigated by applying Particle Tracking Velocimetry (PTV) method. The nozzle angle, injection differential pressure, and atmosphere density were selected as experimental parameters, and the Weber number and dispersion angle of the fuel droplets were measured. The results show that the dispersion angles of the fuel droplets are different depending on the droplet size. Also, the direction of droplet dispersion is greatly influenced by injection conditions, and less influenced by the gas-liquid interaction after injection.
Recently, by addition of Real Driving Emissions (RDE), the man-hour of vehicle development is on the increase for the verification of exhaust emissions in actual vehicle driving. This study proposes a development tool that enables front-loading of RDE using Model Based Development (MBD) at the product planning stage. The worst case of driving condition related to exhaust emission is required to select devices and develop controls that comply with RDE regulations at the product planning stage. Using this MBD tool, the virtual driving evaluations were predicted NOx emissions for each driving pattern. As a result, the worst case of driving condition was extracted, and guidelines for countermeasures to reduce exhaust emissions were provided.
In this study, we considered a method evaluating whether PC mode obtained by operational TPA PC model has a similarity with a vibration mode of the target structure using only operational data. We then utilized a continuous PC mode shape correlation between the target PC mode and the PC modes at around the target frequency. As the result, the quite different tendency was observed among conditions in which the PC mode is similar with a vibration mode or not. By using this procedure, the similarity could be evaluated well.
Object Detection is an important part of autonomous driving system. A popular type of autonomous vehicle requires a minimum sensor configuration. Since omnidirectional camera has a large angle of view, it is suitable for autonomous vehicle. However, the omnidirectional image is distorted in the shape. Therefore, it is difficult to apply existing image processing and machine learning. In this research, we focus on the fact that the omnidirectional image is distorted in the shape but the color does not change and we use neural networks for object detection, considering that neural networks can learn distorted shapes.
This research is to confirm the influence of the difference of the attachment methods of booster seats to the safety performance of child occupants by sled experiments. As a result, in the frontal impact sled experiments, the phenomena, which the slipping up of the seatbelt to the neck and the submarining, were occurred under the bellow 2 combination conditions. 1. Occupant moved forward largely because of the seatbelt structure and 2. Occupant was seated in booster seat fixed by ISOFIX attachment. The occurrences of these phenomena would increase the risk to the child occupant’s neck and abdomen.
The purpose of this study is to quantitatively understand the actual traffic situation between vehicle and motorcycle which is useful for preventing motorcycle accidents. From the video data recorded in Malaysia, we analyzed the behavior of motorcycles such as minimum distance between vehicles and minimum lane position in situations which can lead to rear-end collisions and head-on collisions which the number of vehicle-to-motorcycle fatal accidents in Malaysia is high. These results could help in the development of safety equipment to prevent motorcycle accidents.
For the analysis of accidents and safety education, it is important that the risk evaluation for drive recorder data approximate human perception. This report deals with rear-end collision scenes in the near-miss incident database. It has a manual classification of risk levels, analyzed by using recorded event timing, acceleration, and recorded video. In this study, the deceleration behavior of the driver was inferred from the acceleration data. Also patterns were divided and characteristic timing also examined based on it. The risk evaluation method was examined for the preceding vehicle based on the change in the appearance of the preceding vehicle on the image 0.1 seconds before and after characteristic timing. In the proposed method, evaluation is performed by combining these methods. The validity was examined based on the relationship between the proposed method evaluated and the manual classification of risk levels. In the examination, we divided the cases into short or long times at sudden deceleration. As a result, when the deceleration time was short case, the evaluation value was tended to be higher than in the long case. But it was also seen that the evaluation value was similar when deceleration time was short and manual classification of low risk levels, and when it was long and high levels. By classifying the cases first based on the deceleration time, the proposed method has made it possible to deal with manual risk judgment in most cases.
In platooning using Cooperative Adaptive Cruise Control (CACC), which is being jointly studied by four Japanese domestic truck manufacturers, it is necessary to consider functional evaluations and improvements to realize the platooning system. In actual vehicle experiments, the consideration is limited from the viewpoints of cost and safety. Therefore, in this research, CACC systems are modeled from actual experimental results. The models are validated by simulations.
In order to prevent global warming, the formation of a zero-emissions society is critical. As a solution, the authors propose a “virtual grid system”, which is a new local production and consumption-type of energy system that uses electric vehicles (EV) to store and transport photovoltaic (PV) power. In this paper, the authors have studied the effect of a newly introduced system that combines PV, EV, and household power consumption in different housing types such as a single household, apartment, etc. As the results, the CO2 emissions of the system were reduced by more than 78 % and the spent household energy was reduced by more than 80 % when compared to the conventional system. This is a new functional value specific only to EVs.