In this approach a nonlinear controller for the lateral vehicle dynamics is designed.
The basis for the design is a nonlinear model of the lateral vehicle dynamics in state space representation consisting of three states: The vehicle velocity, the yaw rate as well as the vehicle body sideslip angle (VBSSA). As control variables the yaw rate and the VBSSA are chosen. To assure the vehicle follows the driver's directional intent, the yaw rate is adapted to a desired reference value determined by means of a linear single track model. The second control variable -the VBSSA- is utilized to reduce the lateral forces. Incorporating the VBSSA, the controller's behavior can be significantly improved. Thus, a nonlinear controller is designed which is capable to stabilize the vehicle in critical driving situations.
This nonlinear controller is based on an adaptation of a quality function for the nonlinear model to the one for a linear reference system. Its manipulated variables can be chosen out of the four longitudinal wheel forces and the front wheel turn angle. Additionally, switching between different controllers with different manipulated variables during action is possible. Therein, a change of the active controller depends on characteristic values for the yaw rate and the VBSSA indicating critical situations.
The overall control concept was verified with a simulation software commonly used in industry. The results show a very good stabilization of the vehicle.