Trajectory-based Agile Multi UAV Coordination through Time Synchronisation
In this work, we propose a multi-UAV coordination methodology with trajectory synchronization between the coordination, planning, and control layers. We use probabilistic trajectory mappings (PTM) to find collision-free trajectories through the obstacles. For trajectory tracking, we apply the differential flatness modeling, allowing us to directly map the desired output trajectory, which is parameterized with cubic B-Spline, into the required input sequence. The local support property of B-Splines enables to re-plan of the trajectories without deteriorating entire the shape of the path and the continuity over it. Through this fashion, the trajectory tracking controller generates a required input sequence for given velocity references over the B-Spline sequences, which can be performed by the vehicle. The coordination between the multi-UAV is provided through time synchronization between the trajectories, which are parameterized with B-Splines knot scales and their projected derivatives. We performed experiments in a realistic environment under a motion capture system with multiple nano-size aerial vehicles. The results are given to show the success of the presented methodology for challenging problems such as passing through a small virtual circle in the air for given time sequences.