Closing velocity sensor from Continental Automotive Systems assists driver in braking and enhances passive safety integration strategy

The increasing number of automobiles and a diverse mix of commercial vehicles, light vehicles, three wheelers and two wheelers is increasing safety challenges. Urban areas have seen the most increase in traffic. It has also seen a considerable increase in accidents, which involve personal injury. Considering the increasing instances of accidents in urban areas, systems' supplier, Continental Automotive Systems has developed a closing velocity sensor system (CV). This pre-crash system scans the space in front of the vehicle up to approximately 10 metres ahead in three areas, to the right, the left and straight ahead. If they strike an object ahead of the vehicle they are bounced back. The send and receive unit near the inside mirror then uses the signal to calculate how far away the vehicle in front is, plus the closing speed.

If the distance between vehicles is closing so quickly that a rear-end collision is imminent, the brakes are put on alert mode, i.e. sufficient pressure is built up in the braking system that the brakes respond as soon as the driver applies the brake pedal (prefill). If the driver takes his/her foot off the accelerator, the pre-crash system initiates automatic braking at up to 0.5 g (prebraking). If the driver operates the brake pedal, but with too little sustained pressure, the intervention of brake assist ensures the maximum possible braking power. As a further driver protection function, the system can also tighten the safety belt. During the development of the system it was demonstrated that these measures in combination can prevent a car traveling at up to 35 km/h towards a stationary obstacle from crashing into it, and therefore it can avoid the majority of collisions in urban traffic.

The new pre-crash system delivers benefits for all road users. Vehicle occupants are safer as they travel, because the risk of accident is significantly lower. However, if there should be a crash they are better protected against injury. Not only the seatbelts can be tightened to the optimum degree, but the airbags can also be activated at just the right moment. The occupants in the vehicle ahead are of course also better protected. Rear-end collisions are known to frequently result in long-term damage to the spine. The CV sensor works so sensitive that even single-track vehicles (motorcycles or bicycles) and pedestrians are registered. These road users also benefit from this new type of assistance system. Using the data provided by the CV sensor, the airbag control unit is better able to assess the extent of an impact than it could using data from conventional sensors. The airbags are only deployed when their protective action is really needed. The repair costs following a less severe impact are likely to be significantly lower.

This new sensor provides the automotive industry with a system that makes precrash functionality affordable even for small and mid-range vehicles. "It is easily integrated into the vehicle electronics and does not require any adjustment to the vehicle structure" explains Dr. Ralf Cramer, head of the business unit electronic braking and safety systems at Continental Automotive Systems. "The new sensor system is yet more evidence of our strong position in terms of developing and manufacturing safety systems that are priced attractively enough for use in cars below the luxury range. The CV sensor highlights the functionality of our APIA project that combines active and passive safety for mass-market vehicles. We strongly believe that such comprehensive safety systems should be made available to all vehicle categories". This innovative sensor system, with many of the functions described, will be launched in 2008 in a European-made car.