Abstract:
Multi-robot systems are an important research topic in wide area coverage applications such as hazardous waste clean-up, bomb detection, surveillance, and search and rescue missions. They can work in parallel and complete tasks faster than a single robot. Communications can support cooperation to speed up execution, reduce duplication, and prevent interference. Communication among team members is achieved explicitly or implicitly. In explicit communication, messages are intentionally transmitted and received from robot to robot. In implicit communication, robots observe the environment and other robot actions. Although many systems use explicit communications, in exploration of large, open areas (e.g. stadiums and parks), persistent intra-team digital communications is not guaranteed. Therefore, alternative approaches that do not rely upon message passing throughout exploration are needed. Novel contributions of overcoming communication limitations in wide area coverage include: (1) insight on how information shared between robots that are close has more influence on immediate action selection than information shared between robots that are farther apart. Spatial and temporal locality can be instrumental in determining relevance in subsequent action selection; (2) an approach in which observation leverages spatial and temporal locality to infer state rather than rely on digital messaging; and (3) an approach in which robots use spatial rendezvous to exchange information instead of continuously passing messages. Robots explore an environment in sectors, or designated areas, and periodically meet to communicate map information of what they explored. Simulations and physical experiments were conducted and results suggest both approaches can serve as alternatives to cooperation based on continuous point-to-point communications.
