California Partners for Advanced Transportation Technology

One of the main goals of an Automated Highway System environment is to increase the throughput of vehicles traveling on the highway. By moving vehicles in a platoon (a group of tightly spaced vehicles), the traffic flow capacity can be greatly increased. The control law developed for vehicles to safely travel in a platoon is dependent on the lead and preceding vehicle's velocity and acceleration profiles. This information guarantees string stability (i.e. spacing errors between vehicles do not increase down the chain of vehicles). These profiles are transmitted to the vehicle via wireless communication. Unfortunately, a perfect wireless communication does not exist. In this paper, the effects of various communication delays on string stability will be analyzed. The concept of platooning in an Automated Highway System (AHS) allows a group of vehicles to share information across a wireless local area network (LAN). This sharing of information allows vehicles belonging to the same platoon to maintain a smaller inter-vehicular spacing that would otherwise be possible. Of course, once these platoon/LANs exist on the AHS, a method must exist to add vehicles to a platoon and also to remove vehicles from a platoon. This report also develops handshaking protocols that allow the LANs associated with each platoon to reconfigure themselves in response to any physical changes to the composition of the platoon. Since the LANs operate over a wireless communication system, these protocols are designed to be robust towards packet losses, as well as satisfying certain safety and liveness conditions.