Modeling and simulation of the Automated Highway System

We present the hierarchical structure for the control design of the Automated Highway System (AHS). This control hierarchy has four layers: network, link, coordination, and regulation. The network layer routes vehicles from their origin to their destination. The link layer provides the immediate path a vehicle should follow. The network and link layer controllers are on the roadside. The coordination layer supervises a vehicle's activities and engages the vehicle in different maneuvers as needed. The regulation layer executes the maneuvers by providing the control inputs to the vehicle actuators. We show that this control hierarchy can be used to model different AHS proposals.; The next step is to provide the controller for the control layers. We follow the PATH-AHS proposal of platooning as the means to reduce congestion and increase highway capacity. A platoon is a group of vehicles traveling in close proximity to each other with large inter-platoon distance. In the PATH-AHS proposal vehicles are under automatic control. We describe the internal structure of each control layer and the interfaces between them. There are three basic maneuvers: join, split, and change lane. In the join maneuver two platoons join together to form one platoon. In the split maneuver one platoon is divided into two platoons. In the change lane maneuver a single vehicle changes lane. Since the vehicles are automated, each maneuver use a communication protocol to acquire the permission from the surrounding vehicles to perform the maneuver. The communication protocols are designed to ensure maneuver safety and efficiency.; In order to observe the behavior of any specific proposal and to test, evaluate, and compare different proposals, we simulate the design. We have developed the SmartPath simulation tools for AHS scenarios. SmartPath demonstrates that our modeling approach is sound. SmartPath is a visual simulation package. It provides a graphical interface to view the simulated data (vehicles and highway) in a natural way. SmartPath is a micro-simulation: the behavior of each functional element of the vehicle and highway is individually modeled and simulated. SmartPath is also a distributed simulation, so that different sections of the highway network can be simulated in different processors.