Robust Standoff Target Tracking With Finite-Time Phase Separation Under Unknown Wind

This paper investigates robustness and finite-time stability issues for the phase separation problem in standoff target tracking. First, via a new angle, existing results concerning the stability of the standoff tracking of a stationary target with no wind by a single unmanned aerial vehicle (UAV) are reconsidered and extended; furthermore, a new compact condition for global asymptotic stability is provided. On the basis of the above, the phase separation problem is reexamined within the coordinated standoff tracking context, and globally finite-time stable distributed guidance laws are obtained that can treat simultaneously the convergence toward the desired standoff radius, the desired heading, and the proper angular difference between the tracking team of UAVs. In the sequel, the case of a moving target with wind is accounted for, and robust stability properties regarding the UAV convergence to the guidance vector field are shown. In the analysis, the concepts of total stability, input to state stability, as well as uniformly ultimately bounded stability are used. Finally, distributed guidance laws establishing robust global finite-time stability even in the case of both unknown target and wind velocity are proposed. The proposed guidance laws can track successfully even a maneuvering target as well as a slightly accelerating target but not forever, of course. Simulations demonstrate the feasibility and efficiency of the guidance laws.