Modeling of adaptive passenger airbag systems in car frontal crashes

Paper in proceeding, 1997

The objective of this study was to evaluate whether the effectiveness of a passenger airbag can be increased by making the passenger airbag adaptive to crash conditions, such as severity and type of impact, belt use, and passenger size. Such an adaptive passenger airbag will better cover a wider range of crash situations than a conventional airbag system. In this study, mathematical modeling was performed for the optimization of an existing passenger airbag restraint system. The final solution can be used as reference for the design of an adaptive airbag system. The present study was divided into four steps: (1) a FEM airbag model was developed by using the MADYMO 3D program based on an existing prototype of a passenger airbag; (2) the airbag model was validated against airbag static deployment tests, airbag drop tests, and sled tests; (3) the performance of passenger airbag systems of different volumes was evaluated in terms of injury criteria for front seat occupants of different sizes; (4) a parameter study with different impact conditions and varying levels of variables was carried out to find an optimized design of an adaptive passenger airbag restraint system. Three variables selected for passenger airbag optimization are the airbag volume, the bag pressure, and the size of the ventilation hole. Four input factors that varied in different crash conditions are the dummy size, belted/unbelted, impact speed, and rigid/deformable barrier. The HIC, chest acceleration, chest deflection, neck moment, and axial femur force were calculated in each simulation. The effectiveness of the passenger airbag models was evaluated in terms of the injury criteria of FMVSS 208 and other relevant injury parameters. The influence of the airbag variables on the dummy response was analyzed and discussed. The size of the ventilation hole was found to have the dominating influence on the performance of the airbag. The best effect of the passenger airbag system could be obtained either by using a small airbag with high initial pressure or by using a big airbag with low initial pressure. The findings in the present study indicate that a midsize volume (120-liter) airbag with variable venthole can give front seat occupants of different sizes better protection over a range of crash severities than a conventional big (150-liter) airbag with only one size of venthole. The results from this study can be used for the development of a future adaptive passenger airbag system.