  To plan the trajectories of a large and heterogeneous swarm, sequential or
synchronous distributed methods usually become intractable, due to the lack of
global connectivity and clock synchronization, Moreover, the existing
asynchronously distributed schemes usually require recheck-like mechanisms
instead of inherently considering the other' moving tendency. To this end, we
propose a novel asynchronous protocol to allocate the agents' derivable space
in a distributed way, by which each agent can replan trajectory depending on
its own timetable. Properties such as collision avoidance and recursive
feasibility are theoretically shown and a lower bound of protocol updating is
provided. Comprehensive simulations and comparisons with five state-of-the-art
methods validate the effectiveness of our method and illustrate the improvement
in both the completion time and the moving distance. Finally, hardware
experiments are carried out, where 8 heterogeneous unmanned ground vehicles
with onboard computation navigate in cluttered scenarios at a high agility.
