Integrated control for vehicle lateral dynamics improvements using second order sliding mode

Vehicle dynamics control improves passenger´s safety and comfort. Various active control systems were developed to achieve a given objective; however, these control systems are not designed to work in a cooperative way. This paper deals with the coordination of the braking and steering systems to control the vehicle´s lateral dynamics. When the vehicle reaches its handling limits due to the nonlinear tire forces characteristics, the braking actuator is activated to assist the steering actuator. It remains active until the vehicle recovers its linear behavior, then only the steering controller is activated. Both of the braking and steering controllers are synthesized using a second order sliding mode law by applying the super twisting algorithm known for its robustness and its reduction of the chattering phenomena. The objective is to track the vehicle´s side-slip angle and the yaw rate respectively to their desired values given by a linear reference model. The validation of this coordination strategy is done on a double lane change maneuver at a high longitudinal speed that risks destabilizing the vehicle. The numeric simulation is carried out on a nonlinear seven degree of freedom four wheels vehicle model.