Abstract
Keywords: Safety in Road Traffic, Integrated Safety Concept, Collision Mitigation System, Brake Assist System, Performance Analysis
The increase in safety in road traffic is of great social importance. After the major progress made in past decades, which are primarily largely attributable to the optimization of passive safety, an integrated safety concept is increasingly coming to the fore. In addition to the established systems of active safety, such as ABS, ESP and BAS, vehiclesensing systems are gaining in prominence.
Subject of this paper is the driver assistance systems of Mercedes-Benz passenger cars, which support the driver in collision prevention through warning and braking. Two short-range radar (SRR) sensors behind the front bumper and one long-range radar sensor (LRR) in the radiator grille continuously monitor the traffic ahead in order to detect hazardous situations. Uncertainties in environment recognition, and particularly in terms of the driver's intention, lead to conflicts that must be resolved as optimally as possible in the context of system design. On the one hand, in dangerous traffic situations, the driver should experience the greatest possible benefit, and on the other hand, the systems must keep undesired interventions at an acceptable minimum. Two system characteristics that usefully complement each other are derived from this area of conflict between driver acceptance and system benefits: an autonomously braking collision mitigation system (CMS) and a situation-adaptive brake assist system. The brake assist system closes the intrinsic limitations of the CMS, thus forming a key element in the development of an integrated safety concept.
With regard to collision prevention with the support of CMS, the effective pre-warning time is introduced as performance measure. This is defined as the timeframe that the driver has from onset of the first acoustic-sensory warning with utilization of the autonomous brake intervention in order to initiate at the latest a maneuver that still prevents the collision. In contrast to the warning-only systems, the autonomous brake intervention results in an additional reaction time gain that is particularly effective if the driver reacts slowly. This gives the driver additional time to take evasive action ahead of the obstacle or to come to a standstill using the situation-adaptive brake assist system.