Meeting-Merging-Mission: A Multi-robot Coordinate Framework for Large-Scale Communication-Limited Exploration

Abstract

This letter presents a complete framework Meeting-Merging-Mission for multi-robot exploration under communication restriction. Considering communication is limited in both bandwidth and range in the real world, we propose a lightweight environment presentation method and an efficient cooperative exploration strategy. For lower bandwidth, each robot utilizes specific polytopes to maintains free space and super frontier information (SFI) as the source for exploration decision-making. To reduce repeated exploration, we develop a mission-based protocol that drives robots to share collected information in stable rendezvous. We also design a complete path planning scheme for both centralized and decentralized cases. To validate that our framework is practical and generic, we present an extensive benchmark and deploy our system into multi-UGV and multi-UAV platforms. I. INTRODUCTIONRecently, thanks to the maturity of multi-robot cooperative technology, swarm exploration has received increasing attention in many application area. Multiple robots can explore wider regions in the time unachievable by a single one, with better fault tolerance and uncertainty compensation. However, in actual exploration missions, communication limitation introduces great challenges to multi-robot exploration tasks and makes the advantages brought by multi robots difficult to leverage. In the real-world, especially large-scale environment, it is unrealistic for robots to have global communication capabilities. Besides, transmitting high volumes of sensor data could overwhelm the network capacity. Due to the above realistic factors, the system developed under communication restriction is necessary.The communication limitations are considered from the following two aspects:(1) Limited communication bandwidth (LB). LB makes transmitting the commonly used voxel map or point cloud that are convenient for planning and decision-making exceeds the bearing network capacity.(2) Limited communication range (LR). Robots are constrained to maintain continuous connectivity or execute tasks lonely, introducing great challenges to exploration.To resolve the above issues, we propose a complete framework Meeting-Merging-Mission for multi-robot exploration,

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