Efficiency of UAV-based last-mile delivery under congestion in low-altitude air

Abstract

Emerging unmanned aerial vehicle (UAV) technologies have motivated logistics carriers to seek last-mile parcel delivery through the air so as to benefit from its convenience and flexibility. However, UAV-based delivery services are limited by several binding factors, such as low battery capacities and short delivery range, which in turn require simultaneous use of a large fleet for commercial scale operations. In such cases, congestion in low-altitude air will inevitably arise. This paper investigates self-organized UAV traffic flow in low altitude 3D airspace, and formulates the user equilibrium condition as a set of partial differential equations. We propose a finite element scheme to numerically solve the traffic equilibrium and compute system performance. Two specific test scenarios for last-mile freight delivery systems are studied, including one with a conventional ground-based distribution facility, and the other with a novel concept of airborne fulfillment center. We evaluate the operational cost and energy consumption of these systems under a variety of system configurations. The results provide insights that could be useful for logistic carriers and policy makers to achieve efficiency and sustainability for last-mile delivery.