Airbags learn to see and hear: interaction between crash sensors and driver assistance systems
Sep 2, 2009
Continental is integrating the existing technology in cars so that critical situations can be detected even before a crash occurs. Airbags and other safety systems can then be activated at the most effective moment.
Frankfurt am Main, Germany. Continental, the international automotive supplier, aims to further improve vehicle passenger safety by introducing a new generation of passive safety sensing systems. From data analysis of the ESC, already installed in many vehicles, and by incorporating the radar or camera sensors from driver assistance systems into the passive safety system, it is now possible to detect an imminent accident fractions of a second earlier. This results in airbags, seat belt tensioners and head restraints being activated more quickly so that drivers and front-seat passengers are even better protected. "Linking the crash sensors to the technology employed in driver assistance systems opens up completely new opportunities for passive safety systems to recognize critical driving situations for what they are and categorize them before a crash occurs", stressed Dr. Andreas Brand, Executive Vice President of the Passive Safety & Advanced Driver Assistance Systems business unit in Continental's Chassis & Safety Division at a press conference in Frankfurt am Main.
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All-round airbag protection: controlling safety systems even more precisely and quickly
Airbags for the driver and front-seat passenger, side and head airbags, impact protection for the driver's knees and a curtain airbag for the rear passengers' heads: up to 30 different airbags are now available for installation in today's vehicles to prevent vehicle occupants sustaining severe injuries in the event of an accident. These are in addition to safety belts with tensioners which hold passengers in the optimum position in case of an impact. Over the last 20 years, these passive safety systems have spread from the luxury class into almost every class of vehicle. Further injuries can be avoided, or their consequences made less severe, if the vehicle's sliding roof and windows can be automatically shut immediately before the accident, so that objects are prevented from entering the vehicle, and by bringing the seats and head restraints into the best possible position to prevent serious whiplash injuries.
However, the timeframe for activating these safety systems is extremely short. "One of the challenges for the sensors is to categorize the accident early on so as to provide maximum occupant protection", said Dr. Brand. Up until now, the airbag control system's acceleration sensors only felt the accident on first contact with the other vehicle involved; the system is now learning to see and hear and so can react much earlier.
Using radar, video, infrared and ESC data to predict the accident
Vehicles equipped with driver assistance systems including sensors for monitoring their immediate surroundings enjoy many ways of recognizing hazardous situations and avoiding accidents. If, despite driver assistance, a crash occurs, the sensors provide the passive safety system with valuable data about the accident and help to reduce the severity of the consequences. "Integrating the passive safety elements with the driver assistance systems, the brakes and the electronic stability control system also optimizes occupant protection during emergency braking. It reduces impact energy while the reversible actuators simultaneously carry out their functions", emphasized Dr. Brand. The collision velocity measurement and the impact location and angle calculation allow the airbags to be triggered and the seat belt tensioners to be activated at the appropriate intensity and ensure that the occupants' seats are in the optimum position before the moment of impact.
All this produces huge benefits, stressed Dr. Brand: "At low speeds in urban traffic, the integration of the systems opens up the possibility of completely preventing or at least reducing the severity of neck and spine injuries sustained by vehicle occupants and of avoiding or lowering vehicle repair costs. The result is fewer accidents and insurance companies are already reflecting this in the premiums they charge."
But it is not just the information provided by driver assistance systems about the vehicle's immediate surroundings which can be exploited by the airbag control system. Electronic Stability Control (ESC), which will be a legal requirement for new models in the USA and Europe from 2011, can also provide valuable data about the vehicle's situation. Its lateral velocity in a skid can be calculated by the drive dynamics sensors which are linked to the airbag control unit. If the vehicle leaves the carriageway, the sensitivity of the airbags is appropriately prepared to provide side impact or rollover protection. The result is both earlier and optimized triggering of the passive restraint systems", said Dr. Brand. Head and side airbags can be activated even more quickly so as to reduce the severity of injuries from extremely dangerous pole crashes such as side impacts against trees.
Hearing accident severity: more rapid airbag control due to structure-borne sound sensors
Crash Impact Sound Sensing is Continental's new sensor generation, now in series production, which allows the airbag system to "hear" how severe the accident is. Recognizing the sound waves caused by an impact is based on the same principle used to record earthquakes. Just as rapid and more extreme movements by the seismograph's recording needle indicate an earthquake's strength, when a vehicle collides with an obstacle, the structure-borne sound sensors register the speed at which the body shell distorts and the speed and strength at which the sound waves are transmitted. A complex signal evaluation system, which uses specially developed algorithms to analyze and assess the accident, takes the ultimate decision as to whether the airbags should be initiated or not. In trials under Euro NCAP crash test conditions at a collision velocity of 64 km/h, the structure-borne sound sensor assessed the situation 15 milliseconds earlier as sufficiently serious for it to trigger the airbags. This technology therefore provides considerably more time for the airbags and belt tensioners to be activated and to allow the safety systems to operate more effectively.