Maike Salfeld

Optimal control inputs to affect vehicle dynamics in various driving states

Abstract This paper explores vehicle dynamics in skid maneuvers. First, modeling of vehicle dynamics in skid maneuvers is discussed and a vehicle model suited for the situation is developed. The model is used for analyzing the theoretical maximum stabilizing yaw moment, which can be generated in skidding by vehicle control systems. The maximum yaw moment is found by optimization in an exemplary skid maneuver. From analysis of the results, different underlying physical principles that govern yaw moment generation can be revealed. The sensitivity of the optimization results is analyzed by varying the vehicle geometry and tire force characteristics.

Adaptive Cruise Control: A Behavioral Assessment of Following Traffic Participants Due to Energy Efficient Driving Strategies

Improvement of vehicle safety and driving comfort have been the main objectives of driver assistance systems. Because of the general need to reduce the fuel consumption, the scope of driver assistance systems has been enlarged. Today, Adaptive Cruise Control (ACC) systems are developed which realize a more energy efficient driving style. However, energy optimal driving may lead to a trade-off between energy efficiency, vehicle safety and driving comfort. For example long coasting phases might irritate following drivers and provoke them to approach below the safety distance or overtake the ego-vehicle. This raises the question, how far energy optimized ACC affects following traffic and how the trade-off can be optimized to reach a higher acceptance. Within this work, a system to assess the driving behavior of following vehicles is developed and validated. The system is used to study the behavior of following traffic participants due to energy efficient ACC driving strategies. The results show that the median of the time gap between the following vehicle and ego-vehicle is significant lowered when driving with energy efficient ACC in comparison to driving manually. Whereas, the time to collision shows no significant difference between ACC and manually driven. At last, different concepts are presented which try to find an optimum between efficiency, safety and driving comfort.

The impact of energy efficient driving strategies on rear-end safety

In recent years, driver assistant systems have been introduced that enable the driver to reduce the fuel consumption. Several studies have shown that energy efficient driving has often positive effects on the driving safety. Though, the safety has been mostly evaluated regarding the preceding traffic and does not consider trade-offs due to the disacceptance of following drivers. Therefore, within this paper, the influences of energy efficient driving on rear-end safety are investigated in a study with real traffic. The results show that using energy efficient deceleration strategies before a speed limit, e.g. fuel cut-off or coasting, leads to a significant reduction of the time headway between the following and ego-vehicle. For example, the median time proportion of time headways lower than 0.9 s is increased from 0 to 25 % when the coasting strategy is applied.