  In commercial unmanned aerial vehicle (UAV) applications, one of the main
restrictions is UAVs' limited battery endurance when executing persistent
tasks. With the mature of wireless power transfer (WPT) technologies, by
leveraging ground vehicles mounted with WPT facilities on their proofs, we
propose a mobile and collaborative recharging scheme for UAVs in an on-demand
manner. Specifically, we first present a novel air-ground cooperative UAV
recharging framework, where ground vehicles cooperatively share their idle
wireless chargers to UAVs and a swarm of UAVs in the task area compete to get
recharging services. Considering the mobility dynamics and energy competitions,
we formulate an energy scheduling problem for UAVs and vehicles under practical
constraints. A fair online auction-based solution with low complexity is also
devised to allocate and price idle wireless chargers on vehicular proofs in
real time. We rigorously prove that the proposed scheme is strategy-proof,
envy-free, and produces stable allocation outcomes. The first property enforces
that truthful bidding is the dominant strategy for participants, the second
ensures that no user is better off by exchanging his allocation with another
user when the auction ends, while the third guarantees the matching stability
between UAVs and UGVs. Extensive simulations validate that the proposed scheme
outperforms benchmarks in terms of energy allocation efficiency and UAV's
utility.
