Optimal design of continuously inflated airbag for 12-year-old child occupants with various sitting postures

Owing to the lively nature, children often use a variety of non-standard sitting postures when riding school buses. Current restraint systems in school buses and traditional airbags cannot effectively protect the child occupants with the non-standard sitting postures in frontal collisions. A prototype design of a new continuously inflated airbag is proposed to increase the safety of child occupants. The aim of this study is to determine the injury thresholds of 12-year-old children using the dimensional analysis method, and under the eight mixed conditions, to propose an optimal design of a continuously inflated airbag. First, a simulation model of the restraint system is developed and validated by the experimental test conducted according to ECE R80/GB24406. Then, a coupling model of the restraint system and continuously inflated airbag is built. Second, a standard and three non-standard sitting postures of 12-year-old child occupants and the two crash pulses of school buses are combined to form the eight mixed conditions. Finally, the main design parameters of the continuously inflated airbag are optimized using the non-dominated sorting genetic algorithm III and entropy weight method. A continuously inflated airbag with the optimal configuration can significantly reduce the injuries to the 12-year-old child occupants. Under the original crash pulse, the optimized airbag can provide the best protections for the occupant head under the forward-leaning sitting posture and the occupant femurs under the slouched sitting posture, respectively. Under the higher-speed crash pulse, the protective effect on the occupant head under the standard sitting posture is better than that under the right-leaning sitting posture.