Multi-objective optimization of child restraint system for vehicle side impact

The head and thorax of the child occupant are mainly injured regions in passenger car side impacts. In order to reduce the injury risks of head and thorax, a multi-objective optimization design of child restraint system (CRS) and side airbag is conducted in terms of CRS safety performances. A mathematical model of a child occupant in side collision is developed by using MADYMO software and the validity of the model is evaluated by comparing results between simulation and sled test. For the purpose of minimizing accelerations of child head and thorax, a sensitivity analysis of the design variables is conducted using the orthogonal design of experiment (DOE) and analysis of variance. The primary design variables are therefore determined, including material permeability of side airbag, location of top tether in X-direction and stiffness coefficient of lower anchorage. The objective functions for accelerations of child head and thorax are generated with second-order multinomial regression equations in terms of the determined design variables. Optimization is carried out byusing non-dominated sorting genetic algorithm II (NSGA-II). The optimized configuration of the CRS is obtained by further analysis based on the Pareto-optimal solutions. The results indicate that main design parameters of child restraint system are material permeability 0.037 of side airbag, location −0.25 m of top tether in X-direction, stiffness coefficient 0.5 of lower anchorage. Under the optimized condition, the peak value of head acceleration is minimized by about 24 percent. The peak value of thorax acceleration is declined by about 30 percent