Recently, the development of smart chassis-by-wire systems has established innovative potential and new challenges for path tracking of autonomous vehicles. State-of-the-art brake-by-wire systems already enhanced the vehicle handling and stability for a wide range of operation limits. However, the contradictory operations among the multiple x-by-wire systems and the nonlinearities existed in the path tracking kinematics and tire force dynamics could deteriorate the performance of autonomous vehicles. To address this issue, a path tracking controller is designed involving of four sub-controllers: kinematic controller, dynamic controller, coordination controller, and actuator controller. A desired yaw rate is calculated by kinematic controller to make the lateral deviation global asymptotic stable. A constraint mechanism of desired yaw rate is presented according to the prior knowledge of tyre-road friction and path curvature, in order to prevent losing stability caused by the excessive desired yaw rate. The additional yaw moment is generated by a dynamic controller to make the vehicle yaw rate converge to the desired value and make the vehicle dynamic stable. The path curvature is introduced to supplement the feedforward yaw rate, to improve the response performance under the variant-curvature situation. A constraint mechanism of additional yaw moment is also given based on the control characteristics of x-by-wire actuators, in order to prevent losing stability as a result of the excessive additional yaw moment. The control demands for actuators are derived by the control allocation technique based on the optimization method. By adopting the steer- and brake-by-wire technologies, the fast response and precise control can enhance the lateral control performance for path tracking of autonomous vehicles. The effectiveness of the lateral control system is demonstrated via the high-fidelity Carsim-AMESim-Simulink co-simulation under the typical situations.

CICTP