Numerical method for simulating tire rolling noise by the concept of periodically exciting contact force

For the numerical simulation of tire rolling noise, an important subject is the extraction of normal velocity data of the tire surface that are essential for the acoustic analysis. In the current study, a concept of periodically exciting contact force is introduced to effectively extract the tire normal velocity data. The ground contact pressure within contact patch that is obtained by the static tire contact analysis is periodically applied to the whole tread surface of stationary tire. The periodically exciting contact forces are sequentially applied with a time delay corresponding to the tire rolling speed. The tire vibration is analyzed by the mode superposition in the frequency domain, and the acoustic analysis is performed by commercial BEM code. The proposed method is illustrated through the numerical experiment of 3-D smooth tire model and verified from the comparison with experiment, and furthermore the acoustical responses are investigated to the tire rolling speed.     

Occupant injury risk analysis at NASS/CDS database

Injury information for vehicle occupants from the body regions of the head, thorax, abdomen, and upper and lower extremities, due to the restraints and interior parts of the vehicle, were extracted from the 2009 ~ 2012 NASS/CDS database. For those cases with high occurrence frequency, a detailed and comprehensive data analysis was performed to find the relationship between the accident, occupant, vehicle, and injury data. A numerical frontal impact sled model with the Hybrid III dummy and the GHBMC human body model was constructed to simulate and identify those injury risks according to NASS/CDS. Among the 5,734 injuries to the aforementioned body regions from frontal crashes are, listed by frequency of occurrence, the lower extremity (27.8 %), upper extremity (21.3 %), thorax (15.1 %), face (10.9 %), spine (8.7 %), head (7.3 %), and abdomen (6.9 %). The main injury sources to the head were the windshield, side structure, and steering wheel. For the thorax and abdomen they were the seat belt and steering wheel. For the lower extremity it was the instrument panel. The main injury patterns for the head were the concussion and the contusion. For the thorax they were vessel laceration and lung contusion. For the abdomen they were laceration and contusion of the organs. For the lower extremity they were bone fracture and ligament rupture. The steering wheel and seat positions were main factors affecting head and thorax injury risks. From the sled impact simulation, high injury risks of the head and thorax were assessed respectively at conditions of steering column tilt down and rear most seat position, which correlated well with the findings from the NASS/CDS data analysis.     

Integrated approach to an optimal automotive timing chain system design

Ensuring engine efficiency is a crucial issue for automotive manufacturers. Several manufacturers focus on reducing the time taken to develop and introduce brand new vehicles to the market. Thus, a synergic approach including various simulations is generally adopted to achieve a development schedule and to reduce the cost of physical tests. This study involved proposing a design process that is very useful in the preliminary development stage through effective support from simulations. This type of simulation-based design process is effective in developing timing chain drives; the use of this process, based on results from multiple trials, showed improvements in performance including low friction and vibration, improved durability, and cost-effective part design when compared to conventional processes. This study proposes an integrated approach to the preliminary design of an automotive timing chain system. The approach involves structural and dynamic analyses. The details of the design process are described by using the case of a virtual engine. This study conducted and summarized a dynamic and structural analysis as well as topological optimization to describe a process to obtain optimal results. The results of this study indicated the following improvements in overall performance factors: 12.1 % improvement in transmission error, 10.1 % reduction in chain tension, 46 % reduction in tensioner arm weight, and 11 % reduction in transversal displacement.     

Approximate optimal AUTOSAR software components deploying approach for automotive E/E system

The AUTOSAR has been developed as the worldwide standard for automotive E/E software systems, making the electronic components of different suppliers to be employed universally. However, as the number of component-based applications in modern automotive embedded systems grows rapidly and the hardware topology becomes increasingly complex, deploying such large number of components in automotive distributed system in manual way is over-dependent on experience of engineers which in turn is time consuming. Furthermore, the resource limitation and scheduling analysis make the problems more complex for developers to find out an approximate optimal deploying approach in system integration. In this paper, we propose a novel method to deploy the AUTOSAR components onto ECUs with the following features. First, a clustering algorithm is designed for deploying components automatically within relatively low time complexity. Second, a fitness function is designed to balance the ECUs load. The goal of our approach is to minimize the communication cost over all the runnable entities while meeting all corresponding timing constraints and balancing all the ECUs load. The experiment results show that our approach is efficient and has well performance by comparing with other existing methods in specific and synthetic data set.     

基于时空GPSO-SVM的短时交通流预测

为了提高城市道路短时交通流预测的精度,提出了一种基于时空遗传粒子群支持向量机的短时交通流预测模型.通过主成分分析法对路网原始交通流量进行时空相关性分析,用较少的主成分代替原始交通流量并作为预测因子,在粒子群算法中引入遗传算法的交叉和变异因子,避免粒子群算法陷入局部最优.利用改进后的粒子群算法优化支持向量机参数,得到最优的支持向量机模型,并实现城市道路的短时交通流预测.以长春市路网的实测数据为基础进行了实例验证,结果表明,优化支持向量机参数时,遗传粒子群算法不会陷入局部最优,优化效果更好;与粒子群支持向量机模型和遗传粒子群支持向量机模型相比,所提出预测模型的相对误差波动较稳定,平均预测精度分别提高了4.96%和3.41%.     

Schlieren,Shadowgraph, Mie-scattering visualization of diesel and gasoline sprays in high pressure/high temperature chamber under GDCI engine low load condition

Three visualization methods, Schlieren, Shadowgraph, and Mie-scattering, were applied to compare diesel and gasoline spray structures in a constant volume chamber. Fuels were injected into a high pressure/high temperature chamber under the same in-cylinder pressure and temperature conditions of low load in a GDCI (gasoline direct injection compression ignition) engine. Two injection pressures (40 MPa and 80 MPa), two ambient pressures (4.2 MPa and 1.7 MPa), and two ambient temperatures (908 K and 677 K) were use. The images from the different methods were overlapped to show liquid and vapor phases more clearly. Vapor developments of the two fuels were similar; however, different liquid developments were seen. At the same injection pressure and ambient temperature, gasoline liquid propagated more quickly and disappeared more rapidly than diesel liquid phase. At the low ambient temperature and pressure condition, gasoline and diesel sprays with higher injection pressures showed longer liquid lengths due to higher spray momentum. At the higher ambient temperature condition, the gasoline liquid length was shorter for the higher injection pressure. Higher volatility of gasoline is the main reason for this shorter liquid length under higher injection pressure and higher ambient temperature conditions. For a design of GDCI engine, it is necessary to understand the higher volatility of gasoline.     

Influence of temperature on the tyre rolling resistance

Temperature is a very important factor controlling rolling resistance of road vehicle tyres. There are at least three different temperatures that may be considered as important factors controlling thermal conditions of the rolling tyre. The most common measure of the thermal conditions during tyre rolling is ambient air temperature. The other two are: pavement temperature and “tyre” temperature. Tyre temperature is the most difficult to establish, as temperatures of different parts of rolling tyres differ considerably, thus there is a problem to obtain representative values. In the authors’ opinion, air temperature is the most universal and reliable parameter to measure. The article presents results obtained in the Technical University of Gdańsk during laboratory and road measurements of different car tyres rolling on different pavements. The knowledge of rolling resistance characteristics is important for modelling car dynamics as well as fuel consumption. It is also necessary to establish proper test conditions in the future standardized on-road method of measuring rolling resistance. The results indicate that generally each tyre and pavement combination is influenced by the air temperature in a unique way, but at the same it is possible to propose some general influence factors that may be used to normalize measurements to the standard temperature of 25 °C.     

Influence of the geometric parameters of the vehicle frontal profile on the pedestrian’s head accelerations in case of accidents

The goal of this paper is to determine how the geometry of the vehicle’s frontal profile is influencing the pedestrian’s head accelerations (linear and angular) in car-to-pedestrian accidents. In order to achieve this goal, a virtual multibody dummy of the pedestrian was developed and multiple simulations of accidents were performed using vehicles with different frontal profile geometry, from different classes. The type of accidents considered is characteristic for urban areas and occur at relatively low speed (around 30 km/h) when an adult pedestrian is struck from the rear and the head acceleration variation are the measurement of the accident severity. In the accident simulation 3D meshes were applied on the geometry of the vehicles, in order to define the contact surface with the virtual dummy, similar with real vehicles. The validation of the virtual pedestrian dummy was made by performing two crash-tests with a real dummy, using the same conditions as in the simulations. The measured accelerations in the tests were the linear and angular accelerations of the head during the impact, and these were compared with the ones from the simulations. After validating the virtual model of the car-to-pedestrian accident, we were able to perform multiple simulations with different vehicle shapes. These simulations are revealing how the geometric parameters of the vehicle’s frontal profile are influencing the head acceleration. This paper highlights the main geometric parameters of the frontal profile design that influence the head injury severity and the way that the vehicles can be improved by modifying these parameters. The paper presents an approach to determine the “friendliness” of the vehicle’s frontal profile in the car-to-pedestrian collision.     

Gasket life criteria at low temperatures adopting proportional compensation for loss of flexibility and conformability

In the automobile industry, the service life of gaskets is defined as the time until which a released gasket recovers 60 % of the original compression. It was observed that the recovery curves of gaskets were highly nonlinear at high temperatures, and relatively nonlinear at temperatures above the room temperature. However, it was also noted that the recovery curves of the gaskets at temperatures below room temperature exhibited linearity with respect to the ln(time). Automotive manufacturers demand gasket life criteria that exceed a specific time or the entire life of a car. In the case of gaskets used at lower temperatures, since materials encounter losses in its flexibility and conformability, the definition of service life specifying a 60 % recovery may not be sufficiently safe to eliminate possible leakages. In this study, new gasket life criteria that could be used at low temperatures were proposed. The new criteria were proposed based on the change in Young’s modulus of the gasket material in order to conserve the sealing capability.     

Belief and fuzzy theories for driving behavior assessment in case of accident scenarios

The estimation of the overspeed risk before the accident is among the main goals of this paper. The proposed method uses the Energy Equivalent Speed (EES) to assess the severity of an eventual accident. However, the driver behavior evaluation should take into account the parameters related to the Driver, the Vehicle and the Environment (DVE) system. For this purpose, this paper considers a two-level strategy to predict the global risk of an event using the Dempster-Shafer Theory (DST) and the Fuzzy Theory (FT). This paper presents two methods to develop the Expert Model-based Basic Probability Assignment (EM based BPA), which is the most important task in the DST. The first one is based on the accident statistics and the second method deals with the relationship between the Fuzzy and Belief measurements. The experimental data is collected by one driver using our test vehicle and a Micro-intelligent Black Box (Micro-iBB) to collect the driving data. The sensitivity of the developed models is analysed. Our main evaluation concerns the Usage Based Insurance (UBI) applications based on the driving behavior. So, the obtained masses over the defined referential subsets in the DST are used as a score to compute the driver’s insurance premium.