Emergency Steer & Brake Assist – a Systematic Approach for System Integration of Two Complementary Driver Assistance Systems

Advanced Driver Assistance Systems (ADAS) assist the driver during the driving task to improve the driving comfort and therefore indirectly traffic safety, ACC (Adaptive Cruise Control) is a typical example for a “Comfort ADAS” system. “Safety ADAS” directly target the improvement of safety, such as a forward collision warning or other systems which assist the driver during an emergency situation. A typical application for a “Safety ADAS” is EBA (Emergency Brake Assist), which additionally integrates information of surrounding sensors into the system function. While systems in the longitudinal direction, such as EBA, have achieved a high development status and are already available in the market (e.g. “City Safety” from Volvo), systems in the lateral direction are still in the predevelopment stage. The next logical development step in this case will be the system integration of the Emergency Brake and Steer function. This paper presents an approach to systematically combine longitudinal braking assistance and it’s complementary lateral dynamics into an integral advanced driver assistance system for collision avoidance or mitigation. The system assists the driver during emergency brake and/or steer maneuvers based on driver input, physical aspects and surrounding sensor information. The robust detection of the surrounding and the analysis of the driving situation play a major role regarding the discrimination of a hazard situation from normal driving. The level of assistance is based on the ability and robustness of the sensor to display the picture of the real surrounding and driving situation. The discussed system approach assists by preconditioning the chassis for the oncoming brake and/or evasion maneuver and – in the case of an emergency evasion maneuver initiated by the driver gives a recommendation utilizing steering torque overlay to help the driver to steer along a calculated optimized trajectory. In this respect and beside all technical and physical aspects, the human factor plays a major role for the development of this integral assistance concept. Basis for the development of this assistance concept were subject driver vehicle tests to study the typical driver behavior in emergency situations. Objective was on the one hand to analyze the relevant parameters influencing the driver decision for brake and/or steer maneuvers. On the other hand the evaluation should result in a proposal for a preferable test setup, which can be used for use case evasion and/or braking tests to clearly evaluate the benefit of the system and the acceptance of normal drivers. Definition of assistance levels, warnings and intervention cascade, based on physical aspects and an analysis of driver behavior using objective and subjective data from vehicle tests with untrained drivers are presented.