A Decentralized Architecture for Multi-Robot Systems Based on the Null-Space-Behavioral Control with Application to Multi-Robot Border Patrolling

This paper presents a control architecture for multi-robot systems. The proposed architecture has been developed in the framework of the Null-Space-based-Behavioral (NSB) control, a competitive-collaborative behavior-based control approach. The standard NSB statically determines a set of suitably defined elementary tasks (behaviors) and their priorities, i.e., they cannot be dynamically changed according to mission requirements and environmental constraints. In this paper, a three layer architecture has been designed in order to avoid such a drawback. The single robotic unit (agent) performing the mission is placed on the lower layer. In the middle layer, suitably defined elementary behaviors are defined; these elementary behaviors are then combined, via the NSB approach, in more complex actions. The upper layer is a Supervisor in charge of dynamically selecting the proper action to be executed. As further contribution, the architecture has been applied to the multi-robot border patrolling mission to generate a decentralized, deterministic and non-communicative solution that is robust to faults, and prevents collisions, even in the case of high robot density. Finally, the simulations on a team composed by a large number of robots, and experiments on a real setup, composed by three Pioneer-3DX robots, are provided.