Parametric Study Of Occupant Restraint System Concerning Variations In Occupant Size And Crash Severity

Conventional occupant restraint systems in vehicles are designed for specific crash conditions and occupant sizes.It cannot provide tailored protection to occupants of different sizes in various crash scenarios.To overcome this deficiency,the automobile industry has introduced adaptive restraint system with multiple variable parameters.To determine optimal system configurations is the key problem of the development of the adaptive restraint system.A computer simulation based method was used to investigate optimal configurations of restraint system with the consideration of diversity in occupant and crash severity,and the main influential factors to the injuries of occupants were analyzed.The results can be used for the development of adaptive restraint system in future.A simulation model of a front-passenger-side restraint system was built in MADYMO environment,and a scaling method was used to obtain seven non-standard dummy models with different sizes.The protection performance of the restraint system to these dummies under two different crash severities were investigated.The results indicate that the conventional restraint system cannot provide equivalent protection to these dummies.Dummies with small sizes have larger injury outputs than the big ones.A simulation platform based on the software modeFRONTIER was built.The positioning of seat,seatbelt and dummy can be carried out automatically within the platform.The design space of conventional restraint system was expanded by adding design parameters such as seat position and seatbelt load limiting levels.An optimization method with the combination of Sobol sampling and genetic algorithm was used to search for optimal configurations for the seven dummies under two different crash severities.The restraint system with optimal configurations largely reduced the comprehensive injury value and the protection to dummies with small statures were significantly enhanced.By investigating the obtained optimal system configurations,the mechanisms of restraint system under different crash severities were analyzed and the key influential factors were determined.Among the system parameters,the seat positions show different tendencies under different crash severities.In high-speed crashes,the seat positions tend to be closer to the knee bolster.In this way,the dummy contacts with the knee bolster during the early stage of the crash to get a better restraining effect and a sufficient contact between the head of dummy and the airbag is ensured which helps reducing injury outputs of the head and the neck.In low-speed crashes,the seat positions tend to be far away from the knee bolster to avoid adverse influence from the airbag.The submarining tendencies of dummies in the optimized restraint system were analyzed.The relatively large pretensioning effect used in the optimized system increases submarining tendencies of the dummies.The submarining tendency can be suppressed by altering the characteristics of the seat,the height of the D-ring and the stiffness of the knee bolster.