Enhanced Fixed-time Collision-free Elliptical Circumnavigation Coordination for UAVs

In this paper, a collision-free elliptical target encircling coordination with an improved convergence is constructed for a colony of unmanned aerial vehicles (UAVs). Firstly, an enhanced fixed-time enclosing guidance rule is elaborated that propels UAV to reach the user-defined elliptical path within an explicit time limit free from initial state choices, where a skillfully devised radial error feedback featured with a power term switching between a fractional exponent and a polynomial item is incorporated to enable a faster decaying, and a simple filtering-based unknown system dynamics estimator (USDE) is employed to precisely accommodate the undesired wind uncertainty in a computationally efficient manner. Secondly, to empower

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UAVs with the capability of enclosing coordination and collision elimination with UAV members and static obstacles, a collaborative elliptical encircling protocol is derived by enforcing the consensus of proximal arc length error, releasing the unavoidable acceleration and deceleration occurring in prevailing equiphase-based circular enclosing coordination. Additionally, an orthogonal vector field is devised to strike a better balance between collision avoidance subtask and enclosing subtask. The convergence of enclosing system is analyzed to be uniformly ultimately bounded. Simulations are conducted to evaluate the utility and superiority.