Trajectory Tracking for a Group of Mini Rotorcraft Flying in Formation

In this paper, we study the problem of flight formation control and trajectory tracking control for a group of mini rotorcraft. The goal is to achieve and maintain a stable formation for multiple mini rotorcraft while guaranteeing the tracking of a desired time-varying reference. A two-level controller is developed where a individual control strategy guarantees the stabilization of each mini rotorcraft and a collective control strategy ensures a geometric formation and trajectory tracking. A nonlinear controller based on separated saturations is used as a individual controller to stabilize every mini rotorcraft. In order to achieve a collective behavior, i.e. formation and trajectory tracking, we adopt a leader/follower structure of multiple robot systems. The resulting system allow us to use the centroid of the coordinated control subsystem for trajectory tracking purposes. After a initial transient in which every mini rotorcraft will lock himself to the desired geometric formation, then the center of mass which will converge to the desired trajectory while keeping a stable formation. The analytic results are supported by simulation tests.