Near-Optimal Speed Control in UAV-Enabled Wireless Rechargeable Sensor Networks

In this paper, we study an unmanned aerial vehicle (UAV)-enabled wireless rechargeable sensor network (WRSN), where a rotary-wing UAV travels along a fixed trajectory while providing wireless charging services for a set of sensor nodes deployed on the ground. Given the practical speed-related flight energy model, we focus on minimizing the UAV's flight energy during a time-bounded charging tour by appropriately controlling the UAV's travelling speed, such that the charging demand of each node is satisfied. We first investigate the optimal speed control with the minimized flight energy on arbitrarily-shaped trajectories in a 2D space. We adopt the spatial discretization to tackle the non-convexity of the formulated problem, which is then solved by interior-point method with the provable upper bound of the UAV's flight energy. Next, we develop the optimal speed control for the UAV to travel along a 1D trajectory, i.e., a straight line, which is commonly seen in many UAV applications. Extensive evaluations validate the effectiveness of our speed control design in terms of the UAV's flight energy minimization.