Research On The School Bus Active Airbag For Child Occupants

Currently,Chinese school buses serve for students in primary and junior high schools.These students are 6-15 years old.In 2015 the number of students in Chinese primary and junior high schools is about 169 million based on annual statistics for 2015 released by the National Bureau of Statistics.The potential school bus demand of the students aged 6-15 years old is about 532 500 through simple estimation.Chinese school bus industry has great development prospects. With the promotion of school buses,casualties of child occupants caused by frequent school bus accidents have aroused national attention to the school bus safety.Our school bus is in its infancy and school bus seats are equipped with two-point safety belts with the current national standard.School bus occupant restraint system protection for child occupants in frontal crash is poor,the occupant restraint system needs to be improved.In view of the existing school bus occupant restraint system deficiencies, an active normally open school bus airbag is introduced.Students in primary schools are 6-12 years old. The paper took the research on the airbag effect on the injury of child occupants aged 6, 8 and 12 and the research on optimal parameter set of the active airbag to achieve the protection of child occupants with different ages. The main contents of this paper are as follows:1. On the basis of reading a large number of domestic and foreign relevant documentation, the development and present situation of domestic and foreign school bus safety are concluded and induced, the development status and function of the airbag are introduced. The development and present situation the impact test are introduced.2. Present situation and development trend of child occupant protection and the evaluation criteria for the injury of school bus child occupants are introduced.Domestic and foreign standards and regulations related to school bus frontal impact are elaborated.3. The sled test of school bus frontal impact is introduced, school bus frontal impact occupant restraint system(including front and rear seats, floor, a two-point safety belt) of Hybrid III 5% female dummy and P6 child dummy are built with MADYMO. The simulation and experimental results are compared to verify the model validity.4. School bus active airbag works are introduced. The school bus active airbag model is built with MADYMO. Simulation studies for 6-year-old,8-year-old and 12-year-old dummy are carried out. The protective effects of active airbag on dummies are analyzed. Active safety airbag parameters such as upper tether length, middle tether length, lower tether length, the vent area, the mass flow rate of the gas, the airbag position are choosed for single factor analysis to study their effects on the injury of child occupants with different ages.5. In order to achieve the best protection of school bus active safety airbag for 6-year-old, 8-year-old and 12-year-old child occupants, four parameters separately got by the analysis of the change rate of the comprehensive injury evaluation index WICS or sensitivity screening are used for orthogonal optimum design. Simulation is carried out with MADYMO according to the orthogonal table. The optimal parameter combination of the airbag for children of different ages is obtained.The optimization results of two methods are compared and analyzed.The average WICS of children of 3 different ages is used as the optimization target. Middle tether length, vent area, mass flow rate of the gas, airbag position are choosed as variables for orthogonal optimum design to achieve the best airbag parameter combination that can protect child occupants aged 6,8 and 12 comprehensively.The protection effect of different restraint conditions for children of different ages is analyzed. The results show that the injury values of children with different ages can be effectively reduced under the restraint system with the active airbag and seat belt compared to that under the restraint system with seat belt. 6-year-old, 8-year-old and 12-year-old child occupants’ WICS are respectively decreased by 20.5%,62.8% and 60.0%. Injury indicators of each part of children are below the standard. The protection effect of the airbag which can protect children with different ages comprehensively is obvious when the children are not wearing the two-point seat belt. 6-year-old, 8-year-old and 12-year-old child occupants’ WICS are respectively decreased by 9.3%, 66.7% and 48.4%. Injury indicators of each part of children are still below the standard.