Asynchronous and Synchronous Cooperation

Abstract

Based upon an hierarchical world model with (virtual) roads we describe two different forms of cooperation. Asynchronous cooperation arises if preplanned trajectories of autonomous mobile robots with individual goals overlap. Synchronous cooperation takes place if several robots coordinate their actions in order to fulfill a collective task. We concentrate on all effects that result in the course of intersection passing. If a robot intends to pass an intersection and its destination road is occupied at its beginning the robot must not enter the intersection to keep it free. If there are mutual dependencies that result in a cycle no robot may proceed. We are faced with a deadlock that must be detected by all involved robots and resolved. While intersection passing in its regular form is an example for asynchronous cooperation, deadlock resolution shows cooperative synchronous behavior. We synchronize robots being involved in a deadlock in order to constitute a vehicle formation that moves as a unit at a higher organization level. We examine possible dependency graphs in traffic scenarios and explain the resulting data flow between the affected robots.