Frontal Occupant Restraint System Design Based On The Improved Single-Degree-of-Freedom Occupant-Vehicle Model

Occupant restraint system can reduce occupant injuries effectively in frontalvehicle crash. Restraint system parameters matching result reflects in the occupantinjuries. The more reasonable restraint system parameters match result is, the smalleroccupant injuries are. Test method is the traditional way of occupant restraint systemparameters matching. Test method which contains the sample production, testing,protective effect evaluation, re-production, re-testing, and re-evaluation wastes thetime and increases the cost. Occupant restraint system is developed by using a designmethod which is combining computer simulation and actual test presently. However,restraint system is complex and nonlinear; it contains lots of parameters which has nocorresponding with the occupant injuries. If actual test and computer simulation areonly adopted, the cognition of internal physical principles of occupant restraintsystem won t be enough, and then, the performance driven occupant restraint systemdesign won t be achieved.Occupant energy dissipation in frontal vehicle crash is shown by theSingle-Degree-of-Freedom Occupant-Vehicle model (the SDFOV model). Therelationship between occupant restraint system stiffness, ridedown efficiency andoccupant injuries was studied by using the SDFOV model; a design principle ofoccupant restraint system was given. The principle is to increase the stiffness ofoccupant restraint system in the first part of frontal vehicle collision, reduce thestiffness of occupant restraint system in the latter part of frontal vehicle collision andtake full advantage of the occupant survival space. However, all occupant restraintsub-systems are simplified to a spring model in the SDFOV model, the relationshipbetween restraint system stiffness and detailed restraint sub-systems parameters isnot clear, so the application of this model is limited. The Airbag Analytical Dynamic model (the AAD model) which describes thedynamic relationship between occupant responses and main airbag parameters isestablished based on basic physical theories in the paper. The SDFOV model isimproved by using the AAD model, the spring model of restraint system is split intothe seat belt equivalent spring model and the airbag equivalent spring model. Theseat belt equivalent spring stiffness is related to the seat belt fabric tape stiffness,load limiter and pretensioner stroke. The airbag equivalent spring stiffness is relatedto the airbag volume, mixture quality and vent diameter. The improved SDFOVmodel is solved by a discrete iterative method for arbitrary input (impact pulse) andis verified by computer simulation and test results in the paper.The improved SDFOV model is used to rapidly optimize the main parameters ofseat belt and airbag in the conceptual design phase of the occupant restraint systemdevelopment of a small car. The optimization results are verified by the sled test, theymeet the development goals.In the paper, the SDFOV model is improved by the AAD model. The improvedSDFOV model is used to guide the occupant restraint system conceptual design, theseat belt and airbag parameters are matched rapidly. Based on the matched results,the repeated parameter correction process will be shorted and the computersimulation will be easy. All of these make the occupant restraint system developmentrational and efficient.