Browse Publications Technical Papers 2005-01-0461
2005-04-11

CAE Application for the Layout of an Occupant Classification Sensor Mat 2005-01-0461

For the protection of the unbelted occupants on the front passenger's seat in frontal crashes the airbag is fired according to FMVSS 208 depending on the occupant's size or for children at individual stages. For children seated in a rearward facing child seat or OoP (“Out of Position”) situations the airbag should not be fired. A sensor mat on the seat cushion is developed for the classification of the occupants on the passenger seat (“Occupant Classification System” = OCS). The employed sensors in the mat are activated based on a resistive measuring principle so that a characteristic activation of sensors for particular “classes of occupants” can be achieved.
During the development of such a sensor mat for a particular seat model, a large number of tests with test persons, child seats and special buttock dummies are carried out in order to guarantee a reliable recognition of the seat's occupancy. The benefit of using numerical simulation is in the early phase of the development process. Simulation results can be used for predicting how the system will behave. Moreover, available test results can be analyzed and understood better with the help of the simulation model.
The FE simulation model of the seat and the sensor mat was set up and validated against material and component tests. Furthermore simulation models of rigid test punches with different shapes and child seats as well as special buttock dummies were set up and validated against real test results. The comparison of simulation results with test results showed a good accordance. Mechanisms in the seat which are relevant for pressure measurement can be reproduced in the simulation very well.
Parameter studies have been carried out with the validated simulation models. The variables are stiffness of the seat foam, covering materials and preloading, dummies, child seats, seating positions and environmental temperatures.
Currently, the development of the sensor mat is predominated by testing but based on the gained knowledge it is conceivable to replace some testing programs step by step with simulation in the future. This investigation underlines the relevance and the continuity of the CAE application for the development of sensoric components in the automotive safety.

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