Side impact sensors

Future Trends Networked Satellite Sensors and Side-Impact Sensors... 

The history of airbag development began with mechanical ball-in-tube or roll sensors that made an electrical contact when sufficient energy over a sufficient time was encountered. Because these sensors were essentially digital on-off devices, more complex detection algorithms were difficult to implement and they were not fast enough to be used for the evolving side-impact detection systems. The development of small silicon micromachined accelerometers for less than 5... 

In developing these new algorithms, the requirements for sensors added more of them outside of the central control module for two reasons. First, some types of crash were difficult to detect within the short time frame required for deployment (such as offset pole crashes) and the solution was to provide a high-g precrash sensor within the front of the vehicle. And second, the need for side-impact detection required deployment decisions even faster that the frontal crashes (within approximately 5 ms). Both of these requirements moved accelerometers to satellite positions closer to the perimeter of the vehicle where they are more likely to pick up impacts from small objects. 

The second was the impact of rocks near sensors that may be placed on the floor structure for side-impact detection. In these locations rocks or other debris hitting the bottom of the vehicle can cause high-g shocks greater than 300 g at frequencies above the 400 Hz bandwidth of the accelerometer. The last category involves various small objects such as birds, rocks, tree limbs, balls, or other road debris that can impact the side of the vehicle and thus affect sensors mounted in the B pillar or within the skin of the doors. These can also create high-g forces with high-frequency content. 

Lightning Direct strike Damage to aircraft nose or pitot-static ports can impact sensor accuracy Unlikely to impact both side in identical manner, but note that Captain s primary display and the standby display are fed from port side pitot statics ... 

Since driver s-side airbags were made mandatory in 1984, it is estimated that they have saved thousands of lives (Figure A). The way they work is relatively simple. A mechanical sensor in the front of the vehicle is set off by any sudden impact equivalent to hitting a brick wall at 10 mph. The sensor sends an electrical signal to a gas generator attached to the airbag. 

The essential tasks of the sensor housing are to hold the sensing element in place and to protect it against mechanical impacts or aggressive chemicals. Furthermore, it provides the electrical connection and keeps the reference side clean and separated from the exhaust side. Thimble and planar designs naturally differ from each other because of the tubular or rectangular geometry of the ceramic elements and the fact that the planar element typically includes a heater while the thimble heater is a separate part (Fig. 17.15.11). 

---