PCA - fine-tuning an Early Accident Detection System 14/9/99

September 14^th, 1999
PCA : fine-tuning an Early Accident Detection System

Predicting by analysis
With a new concept for the early detection of accidents, engineers at Mercedes-Benz are aiming to improve occupant protection in future even further, thereby once again consolidating their traditional leading position in the field of innovative safety systems.

Mercedes has unveiled the principle of this innovative system. The working title of the research project is "Predictive Crash Analysis".

The concept is based on findings from the company’s own internal accident research, which has revealed that, in about two-thirds of all road accidents, the actual impact is preceded by a relatively long phase which can be used to draw conclusions on the impending crash and its consequences, so that the appropriate protective systems can be put on early standby.

During this "pre-crash phase", an imminent accident can be indicated by, for example, critical driving manoeuvres such as hard braking, skidding or rapid steering inputs.

The benefits of having ESP, and other modern systems
With the Electronic Stability Program (ESP) and Brake Assist system, Mercedes passenger cars already have standard-fitted on-board systems that automatically detect critical driving situations and trigger the appropriate response.

The sensor-controlled safety bar system for roll-over protection in the SL roadster and CLK convertible is another example of a predictive crash analysis system that has already been implemented.

For the future, additional technical innovations are conceivable for further perfecting early accident detection:

automatic lane monitoring, which Mercedes-Benz has already unveiled for commercial vehicles and buses;

an automatic road condition detection system that detects the adhesion of the road surface and calculates the grip of the tyres in advance;

an automatic speed monitoring system that compares the actual road speed with the relevant traffic regulations and warns the driver;

an electronic map for the navigation system, with special identification of high-risk stretches of road that have been the scenes of frequent accidents;

an automatic occupant monitoring system that detects the size, weight and seating position of the car occupants and takes this data into account when triggering the airbag.

Another system currently in the research stage at Mercedes-Benz is an electronic object detection system that establishes the comparative size of oncoming vehicles and determines their weight on the basis of stored information. With the aid of this system, the electronic control unit can determine for example whether a truck, coach or passenger car is on collision course and how large the anticipated crash angle will be. The anticipated accident severity can then be calculated.

By using a central system that collects data from all the various individual systems and analyses the situation in a split second, early warning of an impending accident can be given to the driver, and, at the same time, the appropriate safety systems can be selectively activated.

Moreover, predictive crash analysis can control the inflation of the airbags as required: in a minor collision, for example, the airbags can be inflated more slowly and "softly", thereby enhancing their protective effect in certain types of accident.

Finally, Mercedes engineers believe that it is conceivable in future for an early warning system of this type to be used to trigger automatic activation of the brakes even before a crash in order to attenuate the consequences of the inevitable impact.

Protection in seven phases
With these developments, the active and passive safety systems of modern passenger cars are coordinated even more efficiently to create a new overall safety concept. This concept consists of a total of 7 phases:

Phase 1) Warning systems inform the car driver that a danger is imminent and that driving style has to be adapted to the road or traffic conditions.

Phase 2) Driver assistance systems such as ESP, Brake Assist or DISTRONIC intervene automatically to correct driving errors that would otherwise severely increase the risk of accident.

Phase 3) Safety systems such as the brake system or the roll-over bar of Mercedes convertibles are automatically activated if the probability of an accident is further increased. The automatic seat belt retractor is also already locked at this stage.

Phase 4) In minor accidents, passive systems such as the crash boxes in the front-end structure of modern Mercedes models now enter into action. Automatic front passenger detection and head restraint positioning are further effective means of both minimizing occupant injury and reducing the costs of an accident in the low speed range.

Phase 5) If there is an acute danger of accident, the safety system uses the information from predictive crash analysis to activate protective systems such as the airbags, seat belt tensioners, sidebags or window bags slowly and in soft mode, depending on the type and severity of accident.

Phase 6) With even more severe danger to the occupants, the restraint systems are rapidly triggered in hard mode, which provides optimal protection in this situation. At the same time, depending on which seats are occupied, the belt force limiters are activated during the crash, as well as the automatic fuel cutout system.

Phase 7) Even after the accident, protective measures can still be needed to assist the rescue of occupants from the vehicle. These measures include, for example, the automatic unlocking of the doors and the automatic emergency call via TELE-AID. In addition, the traffic behind is alerted to the danger by automatic activation of the hazard warning lights.

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