Data collection with a team of capacity-constrained unmanned aerial vehicles assisted by a mobile recharger

Wireless Sensor Networks (WSNs) have been utilized in various applications such as environmental monitoring, precision agriculture, disaster response, and military surveillance. A critical challenge that affects the system lifetime is the limited battery capacity of the sensors. In this paper, we study the sensor data collection problem with a team of unmanned aerial vehicles (UAVs) and a single unmanned ground vehicle (UGV). The UAVs work as data collectors while the UGV provides recharging and data-relaying services to the UAVs. We envision partitioned WSN scenarios, where the communication graph on the initial locations of all sensors is not connected. The objective is to minimize the total time required for the UAVs to collect the data of all sensors. We present a multi-stage online data collection algorithm that plans the paths for the UAVs that do not know the locations of the sensors in advance and are subject to both energy and storage capacity constraints. Our algorithm also plans the path of the UGV and determines the recharging sites for UGV-UAV rendezvous considering not only the limited energy capacity of the UAVs but also the total units of sensor data to be collected by each UAV. We analyze its performance theoretically, in extensive simulations, and on well-known benchmark instances.