Unmanned aerial vehicles conflict detection and resolution in city airspace

Unmanned air vehicles (UAVs) have recently attracted attention of many researchers because of their potential civilian applications. Many of these applications are in the city airspace. Before UAVs are used for civilian applications, a systematic integration of UAVs in non-segregated airspace is needed that allow safe operation of UAVs along with manned aircrafts. One of the critical capabilities for safe operation is conflict detection and resolution (CD&R). The UAVs CD&R problem is studied in this paper. Firstly, the airspace conflict problem is analyzed by geometrical method. Secondly, a hierarchical asynchronous conflict detection method is proposed. The cooperative UAVs conflict resolution method is then studied The conflict resolution problem is casted to a nonlinear optimization problem. When the speeds of conflict involved UAVs are equal, the nonlinear safe separation constraint between two UAVs is transformed into linear constraints and the problem is solved by mixed integer linear programming (MILP). When the speeds of UAVs are unequal, the nonlinear optimization problem is solved by stochastic parallel gradient descent (SPGD) based method. Finally, our approaches are demonstrated in two examples.