Hierarchical control strategy towards safe driving of autonomous vehicles

This paper proposes an intelligent safe driving system (ISDS) for autonomous vehicles. The system utilizes a hierarchical control framework, where the high-level and low-level controllers are responsible for the decision making and motion control respectively. In the high-level controller, two finite-state machines (FSMs) are applied. One of the FSMs identifies the relative positions of the surrounding vehicles to the subject vehicle, and the other one chooses the proper driving behaviors intelligently to deal with the complex situations. In the low-level controller, the double-model-predictive-control structure is designed for the lateral motion control, and the PID feedback control with the inverse model is employed for the longitudinal motion control. The proposed control system is tested in the Simulink/CarSim simulation environment. The results show that the controlled subject vehicle is able to avoid the collision with the surrounding vehicles and acquire the desired speed autonomously. The motion stability is also guaranteed during the accelerating/decelerating and lane changing.