ABSTRACT: A breakup model used in spray combustion simulations was developed to predict the breakup process of spray droplets, which has large influences on the mixture formation and the combustion process in internal combustion engines. Taylor Analogy Breakup (TAB) Model is widely used as a droplet breakup model. Improved TAB (ITAB) Model has been developed by improving model constants and the breakup/non-breakup boundary condition of TAB Model. ITAB Model reproduces the dimensionless breakup time based on the observation results of the single droplet breakup behavior and CFD simulation results. In this study, calculation methods of droplet diameter and droplet velocity after breakup in ITAB Model are modified to avoid fitting model constants during spray analysis. Droplet diameter after breakup is determined by calculating Sauter Mean Diameter and using the droplet diameter distribution after breakup based on the observation results of the single droplet breakup behavior. The calculation constant for Sauter Mean Diameter is a function of Weber number to reproduce the breakup phenomenon of single droplets. Droplet velocity after breakup is calculated based on the energy conservation law of droplets used in Enhanced TAB Model. This model shows that Sauter Mean Diameter after breakup is almost same and perpendicular motion of droplets after breakup is more active than TAB Model. This model also considers the effects of the fuel physical properties on breakup characteristics. Model analysis shows that droplet diameter after breakup of the high boiling point component fuel is larger under same conditions and the effect of temperature change is larger than that of the low boiling point component fuel.

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ABSTRACT: Collision-type prediction models based on pre-crash information are important because there is a relationship between collision type, avoidance operations, and occupant injuries. Thus, they can be applied to autonomous driving systems (ADS) or advanced driver assistance systems (ADAS) to prevent serious accidents or minimize damage during collisions. In this study, we investigated the application of collision-type prediction models based on several machine learning methods and compared their performance to determine the best model based on their f1 scores. The results revealed that the light gradient boosting machine (LGBM) model had a high f1 score that exceeded 0.92, which implied that it could potentially be used for ADS and ADAS applications. Furthermore, a brief analysis was performed on the ranking of various factors, which provided useful insight into the significance of several pre-crash factors and their distributions.

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ABSTRACT: Often in Computational Fluid Dynamics integral forces and restoring moments are calculated, but the location where they should be applied may not always be clear. This is because the location is not intuitive: it is dependent on the vehicle’s velocity and its orientation (e.g. sideslip angle). A technique has been developed to translate the aerodynamic forces to the reaction forces on the vehicle’s tires. In this study, CFD simulation is performed with a 7.5° yaw to look at the effect of cornering. To understand aerodynamic effect on vehicle dynamics one must know the location at which this force is applied. This location is commonly called the center of pressure (COP), but more precisely it should be called the COP-Axis because the force is applied along a line-of-action rather than a point. This paper illustrates that. After knowing the aerodynamic forces and the COP-Axis, the reaction force at each tire is calculated. First, the problem is modeled up as a single force with 4 tires. As one can guess, having 4 tires is over-constraining so this is a static indeterminant problem. In 3D there are 6 equations but now we have 12 unknowns. In order to solve the static indeterminant problem it is modelled up as a deformable body. By taking material property into consideration, the percentage of load that’s transferred to each tire is affected. Using the process described in this paper, reaction forces from each tire have been successfully computed and one can see their effect from aerodynamic loads.

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ABSTRACT: The nozzle hole deposit formation is investigated by the test rig in which deposit formation can be accelerated at various injection pressures, injection durations, and nozzle tip temperatures. The rotational speeds of the fuel supply pump are varied to obtain the different times between injections. The Bosch method and the constant volume chamber with a high speed video camera are used to investigate the effects of deposit in the nozzle hole on injection rate and spray characteristics. The results show the longer time between injections promotes the nozzle hole deposit and affects both the fuel injection and the spray characteristics.

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ABSTRACT: This study discusses robust control problems related to the fall of two-wheel motor vehicles during parking or low-speed driving. The robotic motorcycle includes a new rotary axis that can vary the position of the total center of gravity. Some authors have already reported preliminary control demonstrations using a typical PID controller and simple LQR. Moreover, the mathematical model of a robotic motorcycle derived using multibody dynamics methods and its optimal regulator simulation were developed. However, an experimental investigation of a robust control strategy for practical implementation has not yet been conducted. Therefore, this study proposes a practical method based on applying a sliding mode controller (SMC) to improve robust stability in a real usage environment. Here, we introduce the control system design combining a novel mathematical model, including a minor PID control loop and the SMC, with its hyperplane designed by the frequency-shaped optimal regulator. Finally, its effectiveness is verified by experiments using an actual robotic motorcycle.

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ABSTRACT: The presentation range and position that could not be obtained using conventional side and rear mirrors can be obtained using the camera monitor system (CMS). Studies have proposed the effectiveness of a side–rear wide-view monitor that covers a wide angle from left to right. However, placing such a monitor in the same position as a conventional rear mirror creates an incongruent spatial relation problem because the driver seated on the right seat is forced to shift their gaze point to the left to perceive the right side. Thus, this study clarifies the effects of placing a side-rear wide-view monitor at the driver-centered (front of the driver) position on the drivers’ cognitive load, mental stress, and rearward visual behavior. Based on a driving simulator, the proposed side–rear wide-view monitor was set at three positions: the same position as a conventional rear mirror (vehicle-centered), in front of the driver (driver-centered), and in front of the driver and raised upward (driver-centered-up). Under the driver-centered condition, the oxygenated hemoglobin in the prefrontal cortex and the heart rate decreased and the eye movement became more frequent compared with the other conditions. By placing the side–rear wide-view monitor at the driver-centered position, the driver’s cognitive load and mental stress decreased and the rearward visual behavior was closer to that of skilled drivers. Placing the side–rear wide-view monitor at the driver-centered position shows some benefits for support of rearward recognition in perspective of the effects on cognitive load.

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ABSTRACT: Ego-vehicle localization is a critical technology in autonomous driving systems, and one of the widely used methods for localization is scan matching between a 3D map and real-time LiDAR scan. This method is known to fail due to factors such as an incorrect initial position and orientation for scan matching. In this paper, we propose a simulator-based localization evaluation framework to verify the robustness of localization. By using a simulator, localization can be evaluated without driving a real vehicle, and can be evaluated by creating disturbances such as traffic jams. Our framework also allows to evaluate the robustness of localization by using multiple particles with random errors of the initial position and orientation for scan matching to simulate dead reckoning errors caused by multiple factors such as road surface conditions and tire diameter. In the evaluation experiments, we confirmed that the robustness of localization can be evaluated by applying this method to factors such as sensor setup, disturbances in the traffic environment, and the amount of 3D features in the environment.

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