Decentralized control of cooperative multi-robot systems

Several autonomous robots performing a common task not achievable by a sing le robot must coordinate their actions in order to succeed. A centralized c ontrol strategy may ensure this coordination, but it is often impractical d ue to strong restrictions on required feedback structure, inter-robot commu nications and tolerable time-delays. Decentralized control is shown to be a n advantageous alternative, as it makes no use of explicit communication an d is based only on local information about the robot position and task evol ution. A two stage control structure is proposed. At a higher level, the ta sk's specification is given along with information about the desired change s in the task space. At a lower level, the assigned task evolution is ensur ed by an appropriate control strategy. As an application of the proposed te chnique, we analyze a system of two car-like robots moving a beam to a desi red location. Nonholonomy of the robots, friction phenomena, and sensory fe edback are all taken into account. The robustness of the proposed control s tructure is demonstrated by its ability to handle the obstacle avoidance pr oblem: in order to avoid an obstacle, it is sufficient to have it detected by only one of the robots. Simulation results and our experimental setup ar e presented.