Safety benefits of belt pretensioning in conjunction with precrash braking in a frontal crash

This paper estimates safety benefits of crash with precrash braking maneuvers under different pretensioning control factors. A sled test was conducted at 40 kmph with a lap-shoulder-belted Hybrid III 50^th percentile male dummy to simulate a frontal crash. A multi-body model of the sled test was developed based on the actual situation and verified by test data including the seat belt loads, head and chest injury responses of the test dummy and motion postures of the dummy. An impact pulse with a 0.2-second-long constant deceleration of 0.8 g ahead of crash was loaded on the verification model to simulate the real deceleration and the crash process with precrash braking maneuvers. The protection performance of a 3-point seat belt, a seat belt with pyrotechnic pretensioner and a motorized seat belt was compared, and the motorized seat belt had the best protection effect. Different pretensioning control factors, such as pretensioning time and pretensioning force, had remarkable effects on injury responses of the dummy. This method could also be used to develop advanced occupant restraint systems coupled with precrash systems to integrate vehicle active safety and passive safety.