Bosch has introduced a new sensor system designed to better protect front seat passengers in an accident by deploying the airbag in a more precisely targeted way.

The “iBolt” system measures the forces operating on the four anchor points of the seat frame. From that measurement, the weight on the passenger seat and how the weight is distributed are calculated electronically. This data is then used by the vehicle occupant protection system to determine the best way of deploying the passenger airbag.

Because many car passengers, especially in the USA, travel without their seatbelts fastened, the airbags have to have a large volume and open very quickly. The Federal Motor Vehicle Safety Standard 208 (FMVSS 208 for short) demands an airbag release which is matched precisely to the passenger’s weight. This is guaranteed by the iBolt system which is able to differentiate between a full release for large, heavy people, a restricted release for smaller people and children, and prevention of release for small children, when child seats are used or when the passenger seat is not occupied.

The four sensors of the iBolt system are built into the seat chassis, replacing the normal securing bolts. There is usually no need to alter existing seat designs or modify the system for different kinds of vehicle seats or for differing seat covers. The seat height and thus the passenger’s head space are not affected. And as the sensors also have an overload protection against damage in light collisions and require no special measures to connect them up electronically, the new safety system can be fitted to the vehicle without difficulty.

These improvements have been made possible by fusing classical mechanics and electronics into ‘mechatronics’. The sensor bolt is on the one hand an essential part of the seat support, and on the other hand it measures weight through path measurement by means of Hall-effect sensors. The iBolt control unit built into the seat communicates via a bus system with the central airbag control electronics, which because of the precise four-point measurement receives even more information than the pure weight determination. The iBolt system evaluates the four readings and can recognise the way the person is sitting and any changes in it. This additional information allows the release of airbags with twin or multiple-stage gas generators to be matched to the way the passenger is sitting.

Bosch supplies a comprehensive range of occupant protection electronics for the situation-dependent control of airbags, seatbelt pretensioners and even rollover bars. The intelligent sensors can, for example, recognise front and side impacts as well as potential rollover situations and also take account of the passenger seat occupancy. Further refinement of the seat occupancy recognition will be possible in future by means of an even more exact determination of the way the passenger is sitting. A video-based cockpit sensor system would be able to ‘see’, for example, whether a passenger who does not have his or her seatbelt fastened will fall forwards under emergency braking and whether the airbag should be inflated only partially on collision. Bosch is currently developing such a system for production.