Repositioning forward-leaning passengers by seatbelt pre-pretensioning

Area of Science:

• Automotive Safety Engineering
• Biomechanics
• Finite Element Analysis

Background:

• Occupant positioning is critical for seatbelt effectiveness during pre-crash events.
• Forward-leaning occupants may not benefit optimally from restraint systems.
• Finite element simulations offer a method to study occupant dynamics.

Purpose of the Study:

• To determine the required seatbelt pre-tensioner force and activation time for repositioning an average male occupant.
• To evaluate the influence of Automated Emergency Braking (AEB) and seatbelt type on repositioning effectiveness.
• To simulate occupant repositioning using the Active SAFER Human Body Model (Active SHBM).

Main Methods:

• Utilized finite element simulations with the Active SHBM in a forward-leaning posture.
• Simulated 24 pre-crash scenarios varying AEB activation, seatbelt system (Belt-In-Seat vs. B-pillar), pre-tensioner activation time, and force.
• Analyzed the trajectory of the first thoracic vertebra (T1 X) to assess repositioning to an upright position.

Main Results:

• A minimum pre-tensioner force of 400 N with a Belt-In-Seat system and no AEB was sufficient for repositioning, taking approximately 350 ms.
• With AEB active, 600 N pre-tensioner force activated 200 ms before AEB was necessary, with repositioning times of 200 ms (Belt-In-Seat) and 260 ms (B-pillar).
• The Belt-In-Seat system demonstrated faster and more effective repositioning across all tested conditions.

Conclusions:

• Seatbelt pre-tensioner force, activation timing, AEB presence, and seatbelt type significantly impact occupant repositioning.
• Effective repositioning of a forward-leaning occupant model was achieved under specific parameter combinations.
• Optimized pre-tensioner systems present a feasible strategy for enhancing vehicle safety by repositioning out-of-position occupants during pre-crash events.