Investigation on Unconscious Driver's Posture Change and Body Injury Affected by Motorized Seat-Belt Pretensioner in Full-Frontal Collision with Automatic Emergency Braking

At present, the 2018 China New Car Assessment Program (C-NCAP) regulation puts requirements on the active safety performances of vehicles. New vehicles need to add active safety configurations to get a better achievement in the C-NCAP. The configurations include Forward Collison Warning (FCW) system, Auto Emergency Braking (AEB) system and so on. However, few vehicles are equipped with motorized seat-belts. When the vehicle is about to collide, the AEB system generates braking response before the driver. The deceleration caused by the emergency braking of the vehicle will affect the posture of the driver, such as causing the torso to lean forward and reduce the distance between the steering wheel and the driver. If the vehicle still collides after the emergency braking, the change of the driver's posture will produce adverse effects on the protection performance of the air bag and seat-belt. Through finite element simulation, this paper discusses the relationship between the pre-tightening levels of the active seat-belt and the posture of the driver during the emergency braking. Furtherly, a detailed explanation of the relationship between the pre-tightening levels and the injury of the driver's chest is made. The Total Human Model for Safety (THUMS) biomechanical dummy is used to simulate the driver and the LS-DYNA is used to calculate the case of a frontal collision. There are different scheme models in the simulation. In these models, the seat-belts are set with different pre-tightening levels, and different initial speeds are set for each level. After the emergency braking which generated by AEB system, the models still have the full-frontal collisions at a speed of 50km/h. The results show that when the vehicle is in emergency braking, the forward inclination of driver's torso is inversely proportional to the active seat-belt pre-tightening levels. After the collision, the damage degrees of the driver's chest are also different among the pre-tightening levels.