Automated highway systems: Safe platooning and traffic flow control

Automated Highway Systems (AHS) is a concept intended to increase capacity and safety in current surface transportation systems. The design of control systems for AHS is a challenging problem due to their large scale and hybrid nature. This dissertation addresses two important control problems in the AHS hierarchical architecture of the the California PATH program. The first concerns the design of safe controllers for the regulation layer maneuvers. The second concerns the design of stabilizing flow controllers for the link layer.;In the case of the regulation layer, it is assumed that trafFic is organized into platoons of closely spaced vehicles. This dissertation investigates the conditions to achieve safe platooning under normal mode of operation. The notion of safety is related with the absence of collisions that exceed a given relative velocity threshold. State dependent safety regions for the platoons are designed in such a way that, whenever the state of a platoon is inside these safety regions, it is guaranteed that platoon maneuvering will be safe. It is shown that it is possible to design control laws that keep the state of the platoons inside these safety regions. Velocity profiles for all the single lane maneuvers are derived and a nonlinear velocity tracking controller is designed to execute these maneuvers. This controller attempts to complete the maneuvers in minimum time, without compromising safety. The results obtained allow to decouple the design and verification of the regulation and coordination layers. The overall complexity of the design and verification of the AHS as an hybrid system is therefore greatly reduced.;A link layer controller for the PATH AHS architecture is presented. The controller is derived from a principle of conservation of vehicles. Different topologies of highways are considered, including multiple lane highways in which vehicles have different destinations. It is assumed that the velocity and the change of lane can be commanded for vehicles in a stretch of highway. With the use of Lyapunov stability techniques, it is shown that the control laws proposed in this dissertation stabilize the vehicular density and flow around predetermined profiles. This link layer controller exhibits important properties for implementation: it is distributed, in the sense that only local information is used, and avoids highway dynamics inversion.;The regulation and link layers control schemes presented in this dissertation were implemented and tested using SmartPath-3 AHS simulation software. Simulation results were in complete agreement with theoretical predictions.