Pedestrian Head Protection Research Articles

Research of Hood on Maintaining Performance Balance Between Dent Resistance and Pedestrian Head Protection

Research of Hood on Maintaining Performance Balance Between Dent Resistance and Pedestrian Head Protection

A Hierarchical Prediction Method for Pedestrian Head Injury in Intelligent Vehicle with Combined Active and Passive Safety System.

With the development of intelligent vehicle technology, the probability of road traffic accidents occurring has been effectively reduced to a certain extent. However, there is still insufficient research on head injuries in human vehicle collisions, making it impossible to effectively predict pedestrian head injuries in accidents. To study the efficacy of a combined active and passive safety system on pedestrian head protection through the combined effect of the exterior airbag and the braking control systems of an intelligent vehicle, a "vehicle-pedestrian" interaction system is constructed in this study and is verified by real collision cases. On this basis, a combined active and passive system database is developed to analyze the cross-influence of the engine hood airbag and the vehicle braking curve parameters on pedestrian HIC (head injury criterion). Meanwhile, a hierarchy design strategy for a combined active and passive system is proposed, and a rapid prediction of HIC is achieved via the establishment of a fitting equation for each grading. The results show that the exterior airbag can effectively protect the pedestrian's head, prevent the collision between the pedestrian's head and the vehicle front structure, and reduce the HIC. The braking parameter H2 is significantly correlated with head injury, and when H2 is less than 1.8, the HIC value is less than 1000 in nearly 90% of cases. The hierarchy design strategy and HIC prediction method of the combined active and passive system proposed in this paper can provide a theoretical basis for rapid selection and parameter design.

Realistic Reference for Evaluation of Vehicle Safety Focusing on Pedestrian Head Protection Observed From Kinematic Reconstruction of Real-World Collisions.

Head-to-vehicle contact boundary condition and criteria and corresponding thresholds of head injuries are crucial in evaluation of vehicle safety performance for pedestrian protection, which need a constantly updated understanding of pedestrian head kinematic response and injury risk in real-world collisions. Thus, the purpose of the current study is to investigate the characteristics of pedestrian head-to-vehicle contact boundary condition and pedestrian AIS3+ (Abbreviated Injury Scale) head injury risk as functions of kinematic-based criteria, including HIC (Head Injury Criterion), HIP (Head Impact Power), GAMBIT (Generalized Acceleration Model for Brain Injury Threshold), RIC (Rotational Injury Criterion), and BrIC (Brain Injury Criteria), in real-world collisions. To achieve this, 57 vehicle-to-pedestrian collision cases were employed, and a multi-body modeling approach was applied to reconstruct pedestrian kinematics in these real-world collisions. The results show that head-to-windscreen contacts are dominant in pedestrian collisions of the analysis sample and that head WAD (Wrap Around Distance) floats from 1.5 to 2.3 m, with a mean value of 1.84 m; 80% of cases have a head linear contact velocity below 45 km/h or an angular contact velocity less than 40 rad/s; pedestrian head linear contact velocity is on average 83 ± 23% of the vehicle impact velocity, while the head angular contact velocity (in rad/s) is on average 75 ± 25% of the vehicle impact velocity in km/h; 77% of cases have a head contact time in the range 50–140 ms, and negative and positive linear correlations are observed for the relationships between pedestrian head contact time and WAD/height ratio and vehicle impact velocity, respectively; 70% of cases have a head contact angle floating from 40° to 70°, with an average value of 53°; the pedestrian head contact angles on windscreens (average = 48°) are significantly lower than those on bonnets (average = 60°); the predicted thresholds of HIC, HIP, GAMBIT, RIC, BrIC2011, and BrIC2013 for a 50% probability of AIS3+ head injury risk are 1,300, 60 kW, 0.74, 1,470 × 104, 0.56, and 0.57, respectively. The findings of the current work could provide realistic reference for evaluation of vehicle safety performance focusing on pedestrian protection.

Studying on the design and simulation of collision protection system between vehicle and pedestrian

Pedestrian protection technology has become the most important issue in the field of vehicle safety. The design and simulation method of pedestrian protection system for vehicles is studied based on the Teoriya Resheniya Izobreatatelskih Zadatch theory in this article. The optimal solution of a new type of all-around airbag system mounted to the front of vehicles is presented after performing some Teoriya Resheniya Izobreatatelskih Zadatch analysis tools, such as the component analysis, causal analysis, resource analysis, and contradiction analysis. The digital modeling is carried out on the airbag deployments by SolidWorks, and the simulation analysis is performed on the collision between vehicle and pedestrian head by HyperWorks and LS-DYNA. The results show that the vehicle equipped with the front-end all-around airbag than without can play a better role in pedestrian head protection during the collision, making the maximum value of head injury criterion decrease by 66.7%, effectively reducing the collision damage and verifying the feasibility of the solution.

Optimization design of bonnet inner based on pedestrian head protection and stiffness requirements

Head impact with bonnet is one of the major causes for pedestrian severe injury or fatality in car accidents. This paper proposes a multidisciplinary design optimization method for bonnet inner based on pedestrian head protection along with bonnet stiffness requirement. A finite element (FE) model of a child headform impactor is developed and verified via simulation according to Global Technical Regulation No. 9 (GTR No. 9). Static stiffness analysis and headform collision simulation against one impact point for a particular bonnet are implemented. Parametric design and optimization analysis are carried out. Optimization solution significantly achieves a better head protection effect, which clearly affirms the feasibility of the proposed multidisciplinary optimization method and provides a reference approach to optimal design of engine bonnet inner.

Parameters Optimization of PVB Laminated Glass Based on Pedestrian Head Protection

In order to research the influence of the parameters of laminated windshield glass to pedestrian head injuries in vehicle-pedestrian accident, the adaptive response surface method (RSM) was utilized to optimize the key parameters of the laminated glass i.e. the elastic modulus, yield strength, density and the glass thickness, in which the pedestrian head injury criteria (HIC) and glass crack radius were setting as the objective function. A set of glass parameters was obtained which was the most beneficial to the pedestrian protection. The optimization may provide theory basis for the design and research of PVB laminated windshield.

Bumper contact sensor for pedestrian collisions based on analysis of pedestrian kinematic behaviour

An active bonnet and pedestrian airbag are effective in providing a high level of pedestrian head protection. For triggering the activation of these systems, a reliable sensor that distinguishes a pedestrian collision from collisions against other colliding objects is necessary. In this research, a pedestrian contact sensor based on the pressure of a deformable chamber was investigated from finite-element (FE) analysis. In a simulation of a component test of a chamber impact, the internal pressure of the chamber increased with the volume deformation of the chamber according to Boyle's law. The chamber was installed above the top plane of the bumper energy absorber of a simple car model, and FE simulations of a car–pedestrian collision were conducted. The chamber deformed and its internal pressure increased as the bumper energy absorber deformed during contact with the pedestrian leg. It was shown that the pressure response of the chamber could be detected, irrespective of vehicle shape and structure. This particular pressure response in pedestrian collisions was different from that in collisions into other objects such as a road pole. The contact force of the bumper energy absorber tends to be linear with the pressure change of the chamber. It was shown that a pedestrian collision can be distinguished with high reliability from other colliding objects using the chamber pressure based on the colliding characteristics depending on each colliding object.

Influence of Feature Lines of Vehicle Hood Styling on Headform Kinematics and Injury Evaluation in Car-to-Pedestrian Impact Simulations

Vehicle hood styling has significant influence on headform kinematics in assessment tests of pedestrian impact protection performance. Pedestrian headform kinematics on vehicle front-end models with different hood styling characteristics is analyzed based on finite element modeling. More elevated feature lines near hood boundary and the following continuous hood surface towards fender will result in a different headform motion. It can lead to larger deformation space, more rotation and earlier rebound of the headform impactor, which will benefit the head impact protection performance. In addition, hood geometry characteristics such as hood angle and curvature have effects on structural stiffness. Therefore, inclusion of considerations on pedestrian head protection into the vehicle hood styling design stage may lead to a more effective and efficient engineering design process on headform impact analysis. Language: en

Validation of restoration time for pedestrian headform impactor skin

New technical standards for pedestrian head and leg protection in which the headform and legform impact test is conducted against vehicle bonnet and bumper were introduced in Japan as of April 2013. In the headform impact test, an impactor simulating the pedestrian head is used. To simulate the impact response when the human head is dropped, the headform impactor is fitted with a synthetic resin skin made of polyvinyl chloride. Since the skin is non-metallic, it may become deformed and affect the injury reference value in the case where consecutive tests are conducted. It is considered that the skin is restored after a certain period of time after collision. However, up until the present, the exact time required for the restoration had been unclear. Currently, headform impact tests against vehicle bonnet are conducted at a 2-h interval without any scientific background. Therefore, the purpose of this study is to validate the 2-h time interval required for the skin to be restored after collision. By conducting headform impact tests against vehicle bonnet and drop certification tests regulated by the technical standard at different time intervals, we investigated the restoring time for pedestrian headform impactor skin for consecutive impacts.

Features of Fatal Pedestrian Injuries in Vehicle-to-Pedestrian Accidents in Japan

The number of traffic deaths in Japan was 4,612 in 2011. Looking at the road accident fatalities, it revealed that pedestrians accounted for the highest number in 2011 (1,686, 36.6%). To develop safety countermeasures to decrease the severity of injuries and to reduce the number of deaths in traffic accidents, the detailed characteristics of pedestrian injury in vehicle-to-pedestrian crashes are necessary. The purpose of this study is to understand the scenarios of vehicle accidents in which pedestrians suffer fatal injuries. In the present study, we investigated the characteristics of pedestrian injuries in fatal crashes from accident analyses and compared them to head injury severity levels in impact tests against a road pavement and vehicle contact surfaces. In the accident analyses, we investigated the main body regions injured, that is, the most serious extent of injuries over the whole body of pedestrians by using macro vehicle-pedestrian accident data from database of the Institute for Traffic Accident Research and Data Analysis (ITARDA) of Japan. In comparing the differences in injury frequencies for various body regions between 1999 and 2009, it is noted that the frequencies of pedestrian fatalities due to head injuries were significantly reduced. The result indicated that even though head injuries were the most frequent cause of pedestrian fatalities in traffic accidents, the introduction of pedestrian head protection regulation in Japan in 2005 could be considered effective in reducing fatal head injuries. On the other hand, the frequencies of pedestrian fatalities due to hip injuries increased significantly in sedans, light passenger cars, and light cargo vans. Using the macro accident data in 2009, we investigated the frequency of pedestrian fatalities by gender, age group, vehicle travel speed, and fatal head injuries due to vehicle impacts or road pavement impacts. The results also indicated that the frequencies of female pedestrian fatalities due to hip injuries were significantly higher than those of males. Additionally, the results showed that the frequency of pedestrian fatalities due to hip injuries for the age group of over 65 years was significantly higher than that of the industrial age group (aged 13-59). Focusing on the frequency of pedestrian fatalities due to hip injuries in all age groups, vehicle travel speed appeared likely not to be an extremely important factor in increasing fatal hip injuries. In examining the differences in the frequency of fatal head injuries due to contacts with vehicles or road pavements, it is noted that injury frequency in crashes involving vehicles travelling at high speeds were significantly higher than those at lower speeds for pedestrians over 60 years of age. Focusing on head injury severity levels in impact tests against a road and vehicle surfaces using an adult pedestrian headform impactor, the impacts against a road pavement (HIC 6525) was considered to be more severe than those against vehicle front components with high stiffness (HIC from 2600 to 4032). Language: en

Behaviour of high bumper vehicles in pedestrian scenarios with full finite element human models

The European pedestrian regulations (formerly Directive 2003/102 and currently Regulation 2009/631 and recently modified by Commission Regulation [EU] No. 2011/459) have always approached the protection of lower extremities in pedestrian accidents with tests in the front part of the vehicle using rigid impactors. This approach offers a lot of advantage regarding the repeatability, robustness and reproducibility that these tests need but on the contrary decouple the injury occurrence through the different body areas. It is widely supported to approach pedestrian head protection and lower extremities protection in separate tests; however, there is not such consensus in decoupling pedestrian lower leg injuries from the upper leg injuries, especially in the case of high bumper vehicles. The objective of this paper is to look into the details of this close dependence through a set of simulations with THUMS 50th percentile male pedestrian finite element human model impacted by a wide set of high bumper vehicles. The analysis of both the kinematics and the injury occurrence in these scenarios has shown the strong coupling between the upper and lower leg injuries for this vehicle fleet, requiring therefore assessing both type of injuries at the same time.

Impact Absorbing Characteristics of Engine-Hood Inner Panel Structures for Pedestrian Head Protection

Motor vehicles on the market are required to undergo the pedestrian head protection test since 2004 and engine-hoods need to meet the required standards for pedestrian head protection performance in addition to primary performance. The engine-hood of motor vehicles is evaluated by the pedestrian head protection performance test according to the Head injury criteria (HIC) which is calculated by 3-dimensional coordinate (x, y, z) of acceleration generated on the head impactor. All car manufacturers are recently required to consider protecting pedestrian heads when developing the engine-hood. It is important to control the acceleration time history at the initial stage and late stage for pedestrian head protection. The engine-hood for pedestrian head protection needs to control local rigidity and whole rigidity by just one structure. To solve this problem we focus on inner panels which have a dominant role in absorbing energy. This study also aimed at evaluating the impact characteristics of inner panels adopting folded panels to improve pedestrian head protection by numerical analysis. As a result, it was found that the inner panel could complement the performance of outer panel. In addition, the folded panel structure help to control the amount of displacement and it was effective in the reduction of HIC.

1830 ZETA補強板構造を用いたエンジンフードの衝撃緩衝特性(G04-5 構造特性,G04 材料力学部門)

All car manufacturers are recently required to develop the engine-hood for the purpose of protecting pedestrian heads It is important to control the acceleration time history at the initial stage and late stage for pedestrian head protection The engine-hood for pedestrian head protection needs to control local rigidity and whole rigidity by just one structure. To solve this problem we focus on inner panels which have a dominant role in absorbing energy This study also aimed to evaluate that impact characteristics of inner panels adopting ZETA-stiffened panels improve pedestrian head protection by numerical analysis

G030041 自動車用フードインナーパネルの衝撃緩衝特性

All car manufacturers are recently required to develop the engine-hood for the purpose of protecting pedestrian heads. It is important to control the acceleration time history at the initial stage and late stage for pedestrian head protection. The engine-hood for pedestrian head protection needs to control local rigidity and whole rigidity by just one structure. To solve this problem we focus on inner panels which have a dominant role in absorbing energy. This study also aimed to evaluate that impact characteristics of inner panels adopting ZETA-stiffened panels improve pedestrian head protection by numerical analysis.

Redesign of the vehicle bonnet structure for pedestrian safety

Redesign of the structure of the bonnet to improve pedestrian head protection has recently received considerable attention from automobile manufacturers and industry institutes. The fatality of a head injury is based on the head injury criterion (HIC) value. This HIC value is calculated on the basis of the resultant acceleration of the head’s centre of gravity (hereafter called the head centre) during head impacts. This study analyses the constitution of and variation in the resultant acceleration in head-to-bonnet impacts, and how each component of acceleration exactly contributes to the resultant acceleration of the head centre. This study also considers how the structural design parameters affect each component of acceleration. The causes that make the characteristic variation in the resultant acceleration differ from the optimal characteristic pulse will be analysed and discussed in detail. Based on the results of this analysis, the sudden increase in K (the curvature of the head centre’s motion) after several milliseconds of the impact process must be eliminated. The sudden increase in K in this duration does not depend on the mass and stiffness of the bonnet but does depend on the characteristics of the reinforcement structure. Therefore, a new design of the bonnet reinforcement structure has eliminated the sudden increase in K. The bonnet reinforcement structure, as well as the bonnet thickness, have been designed to make the resultant acceleration of the head centre close to the optimal acceleration pulse. The results of this study contribute to efforts to design an improved vehicle bonnet structure and to pave the way for developing pedestrian protection technologies.

Analyzing pedestrian head injury to design pedestrian-friendly hoods

Head injuries are a major cause of fatalities in pedestrian-car accidents. The HIC (Head Injury Criterion) value, a measure of the fatality risk of a head injury, is calculated from the acceleration of the head’s center of gravity (henceforth, head center) resulting from a head impact. The pedestrian’s head does not impact the hood at a direction normal to the hood’s surface. The direction of motion of the head center may change extremely rapidly upon impact, and normal acceleration may also significantly contribute to the resultant acceleration of the head center. Therefore, pedestrian head protection studies should consider how normal acceleration contributes to the resultant acceleration of the head center. It is necessary to control the resultant acceleration of the head center to produce an optimal characteristic pulse. This study analyzes the composition and variations of the head’s acceleration in head-to-hood impacts, focusing on exactly how the normal and tangential components of the acceleration contribute to the resultant acceleration of the head center. This study also considers how structural design parameters affect each component of the resultant acceleration. Methods to control the resultant acceleration of the head center to produce an optimal characteristic pulse can be proposed based on the results of this study. The analytical models and the results of this study contribute to efforts to design vehicle hoods and pave the way for developing pedestrian protection technologies.

G0300-3-5 歩行者頭部保護を目的とした自動車用ボンネット構造の衝撃緩衝特性([G0300-3]材料力学部門一般講演(3):疲労と衝撃)

All car manufacturers are recently required to develop the engine-hood for the purpose of protecting pedestrian heads. It is important to control the acceleration time history at the initial stage and late stage for pedestrian head protection. The engine-hood for pedestrian head protection needs to control local rigidity and whole rigidity by just one structure. To solve this problem we focus on inner panels which have a dominant role in absorbing energy. This study also aimed to evaluate that impact characteristics of inner panels adopting Miura-Ori structures panels improve pedestrian head protection by numerical analysis.

153 歩行者頭部保護のための自動車用エンジンフード補強板構造の衝撃緩衝特性(実用版・シェル構造の衝撃と応力,OS-13 板・シェル構造の振動・座屈と設計,総合テーマ「伝統を,未来へ!」)

153 歩行者頭部保護のための自動車用エンジンフード補強板構造の衝撃緩衝特性(実用版・シェル構造の衝撃と応力,OS-13 板・シェル構造の振動・座屈と設計,総合テーマ「伝統を,未来へ!」)

255 対人事故時の歩行者頭部保護性能向上を目指したエンジンフード形状の研究(加工と生産システム)

255 対人事故時の歩行者頭部保護性能向上を目指したエンジンフード形状の研究(加工と生産システム)

Characteristics of 3.5 kg pedestrian headform impactor prototypes developed by JAMA–JARI and ACEA–TNO

In 2004, the officially announced Japanese standard for the evaluation of car–front safety performance in terms of pedestrian child head protection required a 3.5 kg headform impactor as a test tool simulating a child pedestrian head. Currently, ACEA–TNO have jointly developed a 3.5 kg headform impactor in Europe. The primary aim of the present study is to investigate the availability of the 3.5 kg ACEA–TNO headform impactor in terms of the Japanese standard. Meanwhile, JAMA–JARI have together developed a 3.5 kg headform impactor in Japan. The secondary aim of our study is to present the physical characteristics and measured head injury criteria (HIC) of the JAMA–JARI and ACEA–TNO headform impactors obtained here as a point of reference for the formulation of the Global Technical Regulation (GTR) standards now under way. The technical specifications regarding mass, outer diameter, moment of inertia, location of centre of gravity, seismic mass location of accelerometers, natural frequency, and biofidelity of these headform impactor prototypes were investigated for each of the respective JAMA–JARI and ACEA–TNO headform impactor prototypes. The skin performance of these prototypes was also determined in terms of Shore hardness, relation of compressive force and deformation, high-velocity certification characteristic, and impact durability against a car bonnet. HIC obtained by both prototypes in car-front impact tests at various locations were also discussed.