Abstract: The occupant restraint system of school bus is the key to protecting the safety of child occupant. The effects of control parameters such as the length of belt, the gas mass flow rate, the installation position, the opening degree of vent hole, the initial pressure of airbag, the initial pressure of exhaust and the distance between seats on the protection results of child occupant are studied in this paper. By using sensitivity analysis, the key parameters for children occupant protection are selected, i.e. the belt length, the vent hole opening degree, the exhaust initial pressure and the distance between seats. Based on the design of experiment with Latin hypercube sampling and polynomial response surface model, the surrogate models for weighted injury criteria (WIC), neck injury criterion N_ij and key airbag parameters are constructed. A multi-objective optimization on WIC and N_ij is conducted by using NSGA-II. The results show that with a belt length of 0.205 m, a vent hole opening degree of 200%, an exhaust initial pressure of 1.15×10⁵ Pa and an inter-seat distance of 0.65 m, WIC and N_ij simultaneously get a small value, reducing by 60.75% and 60.94% respectively, achieving the goal of reducing the neck injury as much as possible while enhancing the overall protection effects of child occupant

Key words: active safety airbag, polynomial response surface model, NSGA-Ⅱ, optimization