Should the Desired Heading in Path Following of Autonomous Vehicles be the Tangent Direction of the Desired Path?

The path-following problem for autonomous vehicles is investigated in this paper. The desired vehicle heading is commonly chosen as the tangent direction on the desired path. This paper points out that the traditional definition of the desired heading may deteriorate the path-following performance, particularly when the vehicle is tracking a path with large curvature. That is because the sideslip angle control and the yaw rate control are conflicting in the presence of sliding effects, and the sideslip angle does not equal to zero when the vehicle is tracking a curve path. This paper further provides an amendment to the definition of the desired heading, which realizes a more accurate path-following maneuver. In the controller design phase, backstepping is used to generate the required yaw rate, and an LQR controller is adopted to obtain the optimal active front steering input. The CarSim-Simulink joint simulation verifies the reasonability of the amendment to the desired heading.