Effect of active seatback reset on lumbar spine injury risk in reclined occupants

The development of intelligent cockpit technologies has contributed to enhanced occupant comfort and an improved travel experience in a reclined seating posture. However, these advancements have also been linked to an elevated risk of lumbar spine injuries in reclined occupants. This study aims to evaluate the influence of active seatback reset (ASR) strategies on lumbar injury risk under frontal impact scenarios. A series of finite element simulations was conducted to investigate the kinematics and lumbar spine loading across varying seatback reset rates (1.551 rad/s ∼ 3.8775 rad/s) adopting ASR for a 30° reclined occupant. Results demonstrated that the seatback reset rate (SRR) significantly affects both the occupant's motion trajectory and lumbar spine injury indices. Specifically, higher reset rates were associated with elevated lumbar injury risk. Nonetheless, ASR strategies contributed to a reduction in lumbar injury risk (27%-36%) in reclined postures. Moreover, lumbar injury risk appeared to stabilize as the SRR decreased. The reset rate of 2.585 rad/s (Case 2) substantially reduces lumbar injury risk. These findings suggest that ASR can reduce lumbar spine injury risk in reclined occupants during frontal impacts.