Effects of seatback angles on passenger kinematics among the longitudinal braking scenario

Abstract

With the development of autonomous vehicles and zero gravity seats, the passengers are more likely to sit in their preferred postures, such as the high reclined positions. This study aims to analyse the passenger kinematics under different seatback angles by volunteer experiments, which is beneficial for future smart restraint system development. For this study, four volunteers were selected to participate in the longitudinal braking experiments from 80 km/h to 0 km/h, and each volunteer repeated 3 times. Among the tests, three seatback angles (25°, 45°, and 60° from the vertical) were introduced, while the seat pan angles were the same. The seatbelt forces, as well as the volunteers’ motions were recorded among the experiments. The experimental results indicated that both head displacement and the first thoracic vertebrae (T1) displacement increased gradually with the increase of the seatback angle. The average T1 displacements for four volunteers under 25° seatback angle were between 180.2 mm to 245.5 mm, while the T1 displacements for 45° seatback angle and 60° seatback angle were between 291.4 mm to 374.3 and 366.2 mm to 444.5 mm respectively. Both shoulder belt force and lap belt force increased with the increase of seatback angle, except for the 60° case of No.1 volunteer, which might due to the muscle activation level difference. In this study, there was no significant correlation between the seatback inclination angle and the amount of seat belt outlet amount. The study is beneficial for active human model validation and future smart restraint system development.