The role of handling characteristics in driver assistance systems with environmental interaction

Future automotive safety functions, such as lanekeeping or collision avoidance, link the vehicle dynamically to its environment. As a result, vehicle motion is determined by a combination of the mechanical system dynamics and the virtual link to the roadway or obstacles. The need for careful design of both the mechanical and control system elements is particularly apparent for these driver assistance systems since control is intended to complement, not cancel, the vehicle dynamics. This paper presents stability requirements for vehicles with a driver assistance system that keeps the vehicle in the lane through the application of virtual forces. When the application point is at the center of gravity, the results indicate a critical speed for understeering vehicles and instability for oversteering vehicles. Shifting the application point of the virtual force to the neutral steer point, however, stabilizes the oversteering case under a critical speed.