  We present a distributed control strategy for a team of quadrotors to
autonomously achieve a desired 3D formation. Our approach is based on local
relative position measurements and does not require global position information
or inter-vehicle communication. We assume that quadrotors have a common sense
of direction, which is chosen as the direction of gravitational force measured
by their onboard IMU sensors. However, this assumption is not crucial, and our
approach is robust to inaccuracies and effects of acceleration on gravitational
measurements. In particular, converge to the desired formation is unaffected if
each quadrotor has a velocity vector that projects positively onto the desired
velocity vector provided by the formation control strategy. We demonstrate the
validity of proposed approach in an experimental setup and show that a team of
quadrotors achieve a desired 3D formation.
