Driver assistance system for lane departure avoidance by steering and differential braking

Lane departure avoidance systems assist actively the driver during inattention or drowsiness and increase driving safety. Most of the lane departure avoidance systems use for the lateral control of the vehicle in closed loop a DC motor similar to the electrical powered steering (EPS) assistance. Important difficulties and limits of this approach are the shared control with the driver on the steering wheel and the vehicle handling at limits. In this paper a combined lateral control using a DC motor on the steering wheel and the differential braking control is investigated to keep the vehicle on the lane. The main objective is to develop lateral control laws which allow a repartition of the control effort in real time between the steering by the steering angle and the steering by the differential braking. This could facilitate a better interaction with the driver and avoid for instance tires saturation, steering angle saturation or excessive lateral accelerations. A joint design of the steering angle control and of the lateral control by differential braking is ensured by minimizing the vehicle reachability set. This is achieved by means of a quadratic Lyapunov function and LMI methods. Preliminary simulation results illustrate the approach and show a very good performance to avoid the lane departure even during curve negotiation.