Enhancing cooperative transport using negotiation of goal direction

Swarm robotics is a relatively new approach to the coordination of a system composed of a large number of autonomous robots. The coordination among the robots is achieved in a self-organised manner: the collective behaviour of the robots is the result of local interactions among robots, and between the robots and the environment. Each single robot typically has limited sensing, acting and computing abilities. The strength of swarm robotics lies in the properties of robustness, adaptivity and scalability of the group [5]. Foraging is a typical task considered in swarm robotics [4]. It can be decomposed in an exploration subtask followed by a transport subtask. The robotic metaphor consists in the search and retrieval of an object. Therefore, the nest is the metaphorical term for the goal and the prey is synonymous of the object to transport. Examples of applications of foraging are toxic waste cleanup, search and rescue, demining and collection of terrain samples. In our work, we address the case in which all robots completely lose sight of the nest during the exploration subtask of foraging. We assume that the robots have partial knowledge of the goal direction. For instance, they may have perceived the nest earlier and kept track of its approximate direction by means of odometry [2]. Using this approximate knowledge, if several robots attempt to transport a heavy prey in different directions they may fail to move the prey at all. Therefore, we introduce a mechanism to let the robots negotiate the goal direction. In order to meet the general principles of swarm robotics [5], this system is fully distributed and makes use of local communication only.