Vehicle road runoff — active steering control for shoulder induced accidents

The safe operation of a passenger/commercial ground vehicle requires continual judgment, mission planning, and driving skills by the operator. The departure of the tires from the prescribed road surface, labeled road runoff, represents a hazardous situation that must be properly handled to prevent unintended consequences. In this instance, the recommended actions are for the driver to recognize the situation, reduce vehicle speed, and then return to the road way in a safe manner. However, drivers may command a large steering wheel angle to immediately return to the paved road surface which can result in vehicle yaw angles which precipitate accidents. In this paper, the potentially dangerous dynamics for a vehicle recovering from road runoff will be explored with an opportunity for steering system intervention. First, a basis for the importance of the problem will be established. Second, the vehicle dynamics and tire/road interface will be examined to demonstrate the "cause and effect" of large steer angles when returning to the road. Finally, the integration of a road runoff recovery strategy algorithm into a steer-by-wire control system will be discussed. Representative numerical results will be presented and discussed.