Effects of seat pan and pelvis angles on the occupant response in a reclined position during a frontal crash

Grébonval, Cyrille; Trosseille, Xavier; Petit, Philippe; Wang, Xuguang; Beillas, Philippe · 2021 · Crossref

DOI: 10.1371/journal.pone.0257292

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Summary

This study investigates the impact of seat pan and pelvis angles on occupant kinematics and injury risk during frontal crashes in reclined seating positions, a configuration anticipated in highly automated vehicles. While reclined seats offer comfort and new activities, accident data suggests they may increase mortality risks, particularly through submarining (sliding under the lap belt). Previous research focused primarily on seatback angles, often fixing seat pan and pelvis angles. This work addresses that gap by systematically varying these parameters to determine their specific effects on safety outcomes using detailed numerical simulations. The researchers employed finite element simulations using the Global Human Body Model Consortium (GHBMC) M50-O detailed human body model, representing a 50th percentile male. The model was placed on a semi-rigid seat with a fixed seatback angle of 40 degrees from vertical. Three seat pan angles (5, 15, and 25 degrees from horizontal) and three pelvis angles (60, 70, and 80 degrees from vertical, representing upright, reference, and slouched postures) were tested. The occupant was restrained by a three-point seatbelt with pretensioners and load limiters, along with a pre-inflated airbag. Simulations subjected the model to two frontal crash pulses: a moderate pulse (50 km/h deltaV) and a severe pulse (56 km/h deltaV). The simulation environment and models were validated against existing post-mortem human surrogate (PMHS) test data to ensure accuracy in predicting kinematics and injury responses. The results demonstrated that both seat pan and pelvis angles significantly influenced occupant response. Submarining occurrence and associated injury risks increased with lower seat pan angles, higher pelvis angles (slouched posture), and greater acceleration pulse severity. The study found that small variations in seat pan or pelvis angles, particularly at a 15-degree seat pan angle, could lead to substantial differences in kinematics and predicted injury outcomes. Additionally, the presence of an airbag and the positioning of lap belt anchorages were shown to affect submarining risks. The simulations successfully captured trends observed in experimental PMHS tests, validating the model's ability to predict complex interactions between the occupant, seat, and restraint systems in reclined configurations. The significance of this study lies in its contribution to the safety design of future automated vehicles. It highlights that seat pan and pelvis angles are critical parameters for occupant protection in reclined positions, not just seatback angles. The findings suggest that specific combinations of seat geometry and occupant posture can drastically alter injury risk, necessitating careful consideration in vehicle interior design. The authors recommend further experimental validation with volunteers to identify comfortable yet safe postural combinations and with PMHS to confirm impact significance. By providing open-source simulation models, the study facilitates reproducibility and further research into optimizing restraint systems for non-driving occupants.

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• evacuation egress