Enhanced Fixed-Time Collision-Free Elliptical Circumnavigation Coordination for UAVs

In this article, a collision-free elliptical target encircling coordination with an improved convergence is constructed for a colony of unmanned aerial vehicles (UAVs). First, 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 is employed to precisely accommodate the undesired wind uncertainty in a computationally efficient manner. Second, to empower 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 the enclosing system is analyzed to be uniformly ultimately bounded. Simulations are conducted to evaluate the utility and superiority.