The role of communication in coordination protocols for cooperative robot teams

We investigate the role of communication in the coordination of cooperative robot teams and its impact on performance in search and retrieval tasks. We first discuss a baseline without communication and analyse various kinds of coordination strategies for exploration and exploitation. We then discuss how the robots construct a shared mental model by communicating beliefs and/or goals with one another, as well as the coordination protocols with regard to subtask allocation and destination selection. Moreover, we also study the influence of various factors on performance including the size of robot teams, the size of the environment that needs to be explored and ordering constraints on the team goal. We use the Blocks World for Teams as an abstract testbed for simulating such tasks, where the team goal of the robots is to search and retrieve a number of target blocks in an initially unknown environment. In our experiments we have studied two main variations: a variant where all blocks to be retrieved have the same color (no ordering constraints on the team goal) and a variant where blocks of various colors need to be retrieved in a particular order (with ordering constraints). Our findings show that communication increases performance but significantly more so for the second variant and that exchanging more messages does not always yield a better team performance.