Automatic path control based on integrated steering and external yaw-moment control

Nowadays improving safety is an indispensable part of research issues in the automotive industry. Due to increased travelling time, accident potentials and also traffic congestions, automated vehicles are seen as a way to increase freeway capacity and vehicle speed while reducing accidents resulted from human errors. In order to guide a vehicle automatically, vehicle lateral motion should be controlled, active steering control (ASC) and direct yaw-moment control (DYC) are two common methods to control the vehicle lateral dynamic, automatically. For higher vehicle lateral acceleration, where the tyres will not be capable of producing enough lateral forces (yaw-moment), ASC could not be useful. In such situation, the advantages of DYC can be clearly observed. In this paper, a novel optimal control law is proposed to control the vehicle path, automatically. The control law uses the vehicle dynamic variables such as the yaw and lateral velocities, lateral offset, and the heading error as well as the road-related variables. These are the road curvature and the lateral offset between the desired path and the vehicle as the feedback/feed-forward signals to produce both the front steering angle and the external yaw-moment signals as the control efforts. Simulation results illustrate the dominant power of the front steering/DYC in the control of the vehicle lateral motion.