On vehicle formations with ring structured communication graphs

Vehicle formations with ring structured communication graphs are considered in this paper. A ring communication graph is a type of directed graph. The ring communication graph in its basic form for a platoon of vehicles consists of information flow from each vehicle to its following vehicle and the lead vehicle receives information from the last vehicle. This causes some implementation issues as the communication distance between the first and last vehicle increases with the increase in size of the platoon. Alternative ring structured graphs may be employed to overcome the communication limitations. We provide a quantitative comparison of the basic and alternative ring graph using the communication time as a metric and employing a token ring protocol. A ring structured communication graph has been applied to two dimensional formations of differential drive robots. A platform consisting of four differential drive mobile robots is considered for experimental evaluation of formation control using ring graphs; square and triangle formations are implemented with non-zero initial spacing errors. We will present and discuss results from these experiments. We also discuss the robustness and stability margin of formations employing ring structured information flow graphs with vehicles subject to disturbing inputs.