Crash Sensing and Algorithm Development for Frontal Airbag Systems Using CAE Methods and Mechanical Tests

Mathematical models in combination with mechanical tests were used to develop a frontal crash sensing system and algorithm. The required sensor closure time for the initiation of driver side airbag deployment was estimated by means of multi body dynamics occupant models. The crash sensing system and algorithm were developed using predictions from a finite element model of the front structure of a passenger vehicle. All models were validated by means of mechanical tests. Generally good agreement was obtained between the predictions from the models and the results from the mechanical tests.

In the sensor closure time analysis two occupant sizes were used, the 50%-ile male and the 5%-ile female occupant. Two restraint conditions were evaluated, no belt and a belt system incorporating a pretensioner. A number of crash pulses of various severity were used. In the analysis proper sensor closure time was found to be the time it takes a free flying mass to travel 94 mm minus 30 ms (inflation time of the airbag).

To properly deploy an airbag system in a crash an airbag initiation algorithm was designed. The algorithm was developed using mechanical test results and mathematical model predictions. In the mechanical tests carried out for this purpose the front structure of a medium size passenger vehicle was mounted on a cart. The cart with front structure was impacting various objects at various impact speeds.

The algorithm was relative velocity based using crush zone and centrally mounted accelerometers. The algorithm was able to discriminate between crashes in which the airbag should be initiated and crashes in which the airbag should not be initiated. The airbag initiation time computed using the algorithm was allowing for timely initiation and inflation of a driver side airbag for protection of a passenger vehicle occupant.