Safe Interaction Between Lateral and Longitudinal Adaptive Cruise Control in Autonomous Vehicles

According to the statistics, driver error is the main reason for the road accidents: this has motivated an intensive research on intelligent vehicles equipped with automated driving technology, active safety and driver-assistance systems so as to enhance the safety of drivers, facilitate vehicle controllability and stability, and improve driving comfort. One of the driver assistant systems currently under development by most automotive manufacturers is the Adaptive Cruise Control (ACC) system. The ACC system, which is an extension of the classic Cruise Control (CC) system, controls both speed and distance to preceding vehicles: the aim of ACC is not only provide the drivers with comfort and safety during driving, but also increase the capacity of roads and reduce fuel consumption. One of the major drawbacks of ACC system solutions commercially available in the automotive industry is the limited performance in cornering situations, where the road presents current/future curvatures. In particular, the interaction between longitudinal and lateral controller systems has not been deeply studied. Moreover, in order to obtain both lateral stability and safe clearance to avoid rear end collisions in critical driving situations, coordinated control of the actuators is necessary without avoiding conflicts caused by the coupling of vehicle dynamics. Summarizing, an implementation of an integrated vehicle dynamics control is far from definiteness. A part of this thesis concerns the parametric vehicle model which is based on a set of vehicle parameters (mass, maximum torque etc.) with realistic nonlinearities in longitudinal and lateral dynamics of vehicle. The longitudinal and lateral control systems are designed to fulfill the objectives and requirements. Since driver acceptance of the proposed control systems is crucial, practical constraints are determined via experimental studies on human driving. Furthermore, in order to allow the driver to personalize the control system in a desired manner, parameterization of control system is provided. An appropriate control structure is adopted to create synergies and safe interaction between longitudinal and lateral controllers, taking into account the previous mentioned aspects, compromising between comfort and safety for various driving situations, in order to obtain both lateral stability and safe clearance of advanced autonomous driving vehicle. This MSc thesis mainly focuses on the design of an Integrated Vehicle Dynamics Control (IVDC) strategy for Adaptive Cruise Control with auto steering application intended to decrease driver’s workload. In severe driving situations, the proposed control strategy is designed based on indexes for driving situations to optimally coordinate the brake and steering actuators to avoid rear-end collision danger and unstable lateral motion of the vehicle. Afterwards, the implementation of the designed controllers has been carried out. Simulations are conducted in Matlab/Simulink by using a set of traffic scenarios which are likely to occur in reality. From simulation results, the performances of designed controllers are evaluated with respect to determined performance specifications. Simulation results have shown that the proposed integrated controller satisfies the performance in terms of autonomous driving, path tracking and collision avoidance for a complete envelope of working conditions.