Roberto Horowitz
Department of Mechanical Engineering
University of California at Berkeley
Berkeley CA 94720-1740
Automated Highway Systems (AHS) is a concept intended to increase
capacity
and safety in current highways. This talk discusses some aspects of
the
hierarchical control of a fully automated AHS design, currently under
development at the California PATH program. In the first part of the
talk,
we present an overview of an AHS architecture that is composed of five
hierarchical layers: physical, regulation, coordination, link and
network
layers. Subsequently, we briefly discuss the function and modeling
abstraction used to describe each layer, as well as the structure of the
control system at each layer of the AHS controller hierarchy.
In the second part of the talk we discuss in some detail two aspects of
the
control system design for this architecture. The first concerns the
design
of safe regulation layer controllers, the second the design of traffic
flow
link layer controllers. In the case of the regulation layer, we assume
that
AHS traffic is organized into platoons of closely spaced vehicles and
present conditions to achieve collision free joining and splitting of
platoons, under normal operating conditions. Velocity profiles for all
single lane maneuvers are presented, as well as a nonlinear tracking
controllers that execute these maneuvers in minimum time, without
compromising safety. Link layer feedforward and feedback traffic flow
controllers are presented for different highways topologies, including
multiple lane highways with multiple vehicle destinations. Lyapunov
stability techniques are used to show that decentralized feedback flow
control laws can stabilize vehicular density and flow around
predetermined
profiles. Finally we present, as an illustrative example, the design of
regulation, coordination and link layer maneuvers for the transit of
automated emergency vehicles, such as ambulances, fire trucks or police
cars. The goal of these maneuvers is to permit an emergency vehicle to
transit on the AHS at a faster velocity than the rest of the traffic,
with
minimal repercussions on the overall traffic capacity of the system.