An algorithm for self-organized aggregation of swarm robotics using timer

Aggregation is a basic collective behavior in biology, and is a prerequisite for many applications of swarm robotics. This paper proposes a new distributed algorithm for aggregation of swarm robotics under the constraints of no central control, no information about positions, and only local interaction among robots. Our control strategy contains two states, Search and Wait, for individual robot, as in the model of probabilistic finite state automata (PFSA). The main difference from PFSA is the way of how individual robot decides to leave from an aggregate. In our approach, each robot in an aggregate has a timer as its lifetime in the aggregate instead of having a leaving probability in PFSA. Further, to make all robots aggregate together, the key idea of our algorithm is that robots in small aggregate have shorter lifetime than those in large aggregate. The lifetime of individual robot in an aggregate is approximated as the lifetime of the aggregate, by making all the timers of the robots in the same aggregate have the same time settings, where the time is proportional to aggregate size and is updated only with the increase of aggregate size. By choosing linear function as the time setting of the timer, experiments based on simulator have been done. The results show that our algorithm is successful and scalable for large scale of robots, and indicate that the performance of the aggregation of all robots is improved by decreasing the lifetime of uncompleted aggregate in high robot density or increasing it in low robot density.