  UAV collective motion has become a hot research topic in recent years. The
realization of UAV collective motion, however, relied heavily on centralized
control method and suffered from instability. Inspired by bird flocking theory,
a control strategy for UAV collective motion with distributed measure and
control methods was proposed in this study. In order to appropriately adjust
the inter-agent distance suitable for realization, the control law based on
bird flocking theory was optimized, and the convergence of velocities and
collision avoidance properties were presented through simulation results.
Furthermore, the stable collective motion of two UAVs using visual relative
information only with proposed strategy in both indoor and outdoor GPS-denied
environments were realized.
