Relative localization for distributed multi-robot systems via sound relaying

Owing to the propagation attenuation, the range of sound-based localization is limited. A sound-relaying method is proposed to realize relative localization for a distributed multi-robot system in a larger area. Each robot is equipped with one buzzer and four microphones for sending and receiving sound signals, respectively. The robots are regarded as nodes of a multi-hop and connected network, i.e., there is at least one other node within the effective sound-sensing range of each node. All the robots send sound signals successively and the number of hops between any two nodes is identified. The relative location of any two robots is then calculated using rotating coordinate transformation. Outdoor experiments with five self-made small mobile robots validate the feasibility of the proposed relative localization method.