Investigation of lumbar injury in out-of-position occupants via seat back angles under AES

The effects of seatback recline angles and occupant displacement during emergency steering maneuvers on lumbar injury trends were investigated. A collision simulation environment was created using the AC-HUM model combined with a partial vehicle model. Under varying seatback recline configurations, two pre-collision scenarios were simulated: with and without autonomous emergency steering (AES) intervention. Kinematic and dynamic response analyses revealed that increased seatback recline angles and lateral out-of-position dynamics significantly increased lumbar injury propensity while compromising the protective efficacy of seatbelt and airbag systems in nonstandard postures. This research provides critical insights into injury mechanisms associated with complex occupant displacement postures during pre-impact phases.