Different levels of automation technology strategies have been proposed to improve highway safety and congestion. This paper addresses the problem of the hybrid control of autonomous vehicles driving on automated highways. Autonomous vehicles do not communicate with each other or the infrastructure. Two problems must be considered: a vehicle driving in a single-lane highway must never collide with its leading vehicle; and a vehicle entering the highway at a designated entry junction must be able to merge from the merging lane to the main lane without any collision. To solve these problems, each vehicle is equipped with a hybrid controller, consisting of several continuous control laws embedded inside a finite state automaton. The automaton specifies when a given vehicle must enter the highway, merge into the main lane, yield to other vehicles, exit from the highway, etc. The continuous control laws specify what acceleration the vehicle must have in order to avoid collisions with nearby vehicles. By carefully designing these control laws and the conditions guarding the automaton transitions, three important results are demonstrated. First, the initial conditions guaranteeing that a following vehicle never collides with its leading vehicle are stated. Second, this first result is extended to a lane of autonomous vehicles. Third, it is proved that if all the vehicles are equipped with the hybrid controller, then no collision can ever occur, and all vehicles either merge successfully or are forced to drop out when they reach the end of their merging lane. The outcome of a highway microsimulation programmed in a hybrid systems simulation language called SHIFT and modeled after the Katy Corridor near Houston, Texas is shown: one single-lane highway can accommodate 4000 vehicles per hour with neither drop-outs nor traffic congestion. The microsimulation demonstrates that SHIFT is appropriate for designing safe control laws for autonomous highway systems.


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  • Accession Number: 00986606
  • Record Type: Publication
  • Files: TRIS, ATRI
  • Created Date: Feb 5 2005 12:00AM