Study on the Impact of Vehicle Pitch During Braking on Pedestrian Leg Injuries

With the increasing prevalence of Automatic Emergency Braking Systems (AEB) in vehicles, their performance in actual collision accidents has garnered increasing attention. In the context of Active Emergency Braking (AEB) systems, the pitch angle of a vehicle can significantly alter the nature of collisions with pedestrians. Typically, during such collisions, the pedestrian's legs are the first to come into contact with the vehicle's front structure, leading to a noticeable change in the point of impact. Thus, to investigate the differences in leg injuries to pedestrians under various pitch angles of vehicles when AEB is activated, this study employs the Total Human Model for Safety (THUMS) pedestrian finite element model, sensors were established at the leg location based on the Advanced Pedestrian Legform Impactor (aPLI), and a corresponding vehicle finite element model was used for simulation, analyzing the dynamic responses of the pedestrian finite element model at different pitch angles for sedan and Sport Utility Vehicle (SUV), and comparing injury indicators for the thigh, lower leg, and knee joint. The results indicate that the vehicle's pitch angle reduces the elongation of the medial collateral ligament (MCL) in the pedestrian's knee and increases the maximum bending moment of the thigh. For sedan with pitch angles, the maximum bending moment of the pedestrian's lower leg decreases at a vehicle speed of 40 km/h and increases at speeds of 30 km/h and 20 km/h. The impact of SUV on the maximum bending moment of the lower leg is opposite to that of sedan. This study holds guiding significance for optimizing vehicle design, enhancing the effectiveness of AEB systems, and establishing stricter pedestrian protection standards