Abstract: The child occupant restraint system is an important means of protecting the child occupants in vehicles, in particular, school bus. In this paper, the active airbag for 12-year-old child is optimized. Firstly, the effects of seven parameters, i.e. the lengths of the upper, middle and lower straps, the opening percentage of vent valve, the mass flow rate of gas, the installation height and the opening pressure of airbag on the protection results of airbag on 12-year-old child are studied. Then by sensitivity analysis, three key control parameters of active airbag are found to be the length of upper strap, the opening percentage of vent valve and the opening pressure of airbag. Finally, by using the technique of the design of experiment with Latin hypercube sampling, combined with the construction of response surface model with second-order polynomial for the relationship between weighted injury criterion (WIC) and three key parameters of airbag, an optimization is conducted on the three key parameters of airbag. The results show that with an upper strap length of 0.205 m, a vent valve opening percentage of 1.8 and an opening pressure of 1.16×10⁵ Pa, the WIC of a 12-year-old child can reach the minimum value of 0.240 5. Compared with original airbag parameters, i.e. an upper strap length of 0.235 m, a vent valve opening percentage of 1.0 and an opening pressure of 1.25×10⁵ Pa, the optimized airbag achieves a 24.75% reduction in WIC for 12-year-old child

Key words: child occupant, active airbag, Latin Hypercube sampling, second-degree polynomial response surface model