Constrained Moving Path Following Control for UAV With Robust Control Barrier Function

This paper studies the moving path following (MPF) problem for fixed-wing unmanned aerial vehicle (UAV) under output constraints and wind disturbances. The vehicle is required to converge to a reference path moving with respect to the inertial frame, while the path following error is not expected to violate the predefined boundaries. Differently from existing moving path following guidance laws, the proposed method removes complex geometric transformation by formulating the moving path following problem into a second-order time-varying control problem. A nominal moving path following guidance law is designed with disturbances and their derivatives estimated by high-order disturbance observers. To guarantee that the path following error will not exceed the prescribed bounds, a robust control barrier function is developed and incorporated into controller design with quadratic program based framework. The proposed method does not require the initial position of the UAV to be within predefined boundaries. And the safety margin concept makes error-constraint be respected even if in a noisy environment. The proposed guidance law is validated through numerical simulations of shipboard landing and hardware-in-the-loop (HIL) experiments.