Dynamic Route Planning for a USV-UAV Multi-Robot System in the Rendezvous Task with Obstacles

The marine multi-robot system, which consists of unmanned surface vehicles (USVs) and unmanned aerial vehicles (UAVs), would provide a promising alternative for conducting complex and hazardous marine missions with reduced costs and human involvement. However, the energy issue of the UAVs substantially limits the practical application of this cooperative multi-robot system in maritime tasks. In order to efficiently guarantee the energy replenishment for the UAVs, this paper presents a dynamic route planning strategy to solve the route planning problem for a USV-UAV multi-robot system, with the USVs traveling as mobile charging stations on the sea with obstacles. Based on the graph theory and receding horizon control (RHC) strategy, we formalize the dynamic route planning problem into a dynamic multiple generalized traveling salesman problem (DMGTSP). A heuristic approach is utilized to solve the optimization problem at each control step in a receding manner. The proposed strategy is compared with the global horizon strategy in different case studies with static and moving obstacles. A lake experiment is conducted to validate the developed dynamic planning strategy. The results indicate that the dynamic route planning approach enables the USV-UAV cooperative system to fulfill the recharging task successfully and efficiently by periodically rendezvousing at varying locations during the long-term mission.