This paper presents a sequential collision-free auto-landing strategy for cooperative control of multiple fixed-wing UAVs. It is assumed that the UAVs are initially in an equally spaced circular formation over a predefined landing point. The proposed approach involves a pair-wise leader-follower configuration and generates a higher order polynomial based 3D spline paths for the UAVs to follow. The acceleration constraints used in path generation are explicitly taken into consideration while calculating guidance commands for path following, using a nested saturation based 3D guidance law. The k-nearest neighbors algorithm is employed to generate virtual way-points which are then used to calculate guidance commands by projecting the points onto orthogonal planes. Minimum separation between agents is achieved by formulating a coordination law using linearization techniques that generate thrust commands from velocity profiles. Simulation results showcase the validity of the proposed algorithm.
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