Seating posture is a critical factor influencing the severity of injuries sustained by children in frontal collisions. Following activation of an automatic emergency braking (AEB) system, children are unable to maintain their initial seating postures. Children are more likely to adopt non-standard seating postures compared with adult occupants. The activation of AEB system can exacerbate the phenomenon of “out-of-position” among children. This study focuses on 12-year-old children as representative occupants. Its objectives are threefold: first, to investigate how children’s sitting positions change after AEB activation when they are initially seated in various postures; second, to analyze the kinematic responses and associated injury risks during collisions with and without AEB activation; and third, to propose a novel prototype design of an intelligent strip-shaped airbag and conduct design optimization to enhance its protective performance. After AEB intervention, children exhibit forward-leaning movements across multiple body regions. The head, neck, left shoulder, and thorax of the child initially seated in the pre-submarining posture demonstrate greater horizontal displacement compared with those in the standard and outboard-leaning postures. Compared with the collision scenario without AEB, significant reductions are observed in the head injury criterion, upper neck shear force, occipital extension moment, left and right femur forces, and weighted injury criterion. However, certain injury values for specific body regions still exceed their respective thresholds. The optimized airbag configuration is as follows: strip air bag volume of 21 l, gas mass-flow proportional coefficient of 1.06, vent valve opening pressure of 1.2290 × 105 Pa, and vent valve opening degree of 2.2. This configuration demonstrates superior protective performance. When both AEB and the optimized airbag are activated, children receive the highest level of protection, outperforming scenarios without AEB or with AEB activation alone.
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