  The utilisation of unmanned aerial vehicles has witnessed significant growth
in real-world applications including surveillance tasks, military missions, and
transportation deliveries. This letter investigates practical problems of
formation control for multiple nano-quadrotor systems. To be more specific, the
first aim of this work is to develop a theoretical framework for the
time-varying formation flight of the multi-quadrotor system regarding
anti-collisions. In order to achieve this goal, the finite cut-off potential
function is devoted to avoiding collisions among vehicles in the group as well
as between vehicles and an obstacle. The control algorithm navigates the group
of nano-quadrotors to asymptotically reach an anticipated time-varying
formation. The second aim is to implement the proposed algorithm on Crazyflies
nanoquadrotors, one of the most ubiquitous indoor experimentation platforms.
Several practical scenarios are conducted to tendentiously expose
anti-collision abilities among group members as well as between vehicles and an
obstacle. The experimental outcomes validate the effectiveness of the proposed
method in the formation tracking and the collision avoidance of multiple
nano-quadrotors.
