Integrated trajectory and path tracking of under-actuated and over-actuated cars up to the handling limits

An increasing number of production cars are equipped with vehicle automation systems, which depend on a stable path or trajectory tracking. Nowadays, many cars come with several additional actuators like a rear-wheel-steering that can and should be considered for an efficient design of the tracking controller. In this paper, an integrated trajectory and path tracking approach for under-actuated and over-actuated vehicles is presented. The possibility of decoupling translational and rotational motion for over-actuated cars is specifically utilized to stabilize the vehicle due to the tracking goal. This allows a stable or a dynamic vehicle behavior, depending on the requested path or trajectory. The control system architecture is set up in a hierarchical way. First, the desired vehicle motion is calculated in the kinematic tracking control featuring path and trajectory tracking control of the vehicle motion, which is described in the Frenet frame. Second, an optimization-based model inversion determines suitable actuator setpoints to achieve the desired vehicle behavior. A previously published double track model is extended to enable the combined calculation of longitudinal and lateral vehicle dynamics. Simulations featuring different actuator sets illustrate the performance of the proposed tracking control system.