Optimal Load Balancing of Cooperative UAV-UGV Parcel Pickup to Minimize Completion Time

In this study, we investigate an optimal load balancing of cooperative parcel pickup between an unmanned aerial vehicle (UAV) and an unmanned ground vehicle (UGV). By considering practical aspects, such as the movement characteristics of each vehicle and the avoidance of no-fly zones for the UAV, we aim to optimize the three-dimensional trajectories and pickup strategies of the two vehicles to identify the shortest route to minimize pickup completion time. To deal with the nonconvex optimization problem, we employ a successive convex approximation to convert the original problem into a convex form for optimization variables, and we also use a penalty convex-concave procedure to retain the binary natures of the control parameters that are required to design the pickup strategy. We also propose a two-stage iterative algorithm based on interior-point methods to solve the relaxed convex problem to find suboptimal solutions. The simulation results confirm that the proposed scheme can successfully allow the UAV and UGV to follow the shortest effective path and thus improve pickup completion time through load balancing, while outperforming the baseline schemes under various scenarios.