  In this paper, an adaptive super-twisting controller is designed for an agile
maneuvering quadrotor unmanned aerial vehicle to achieve accurate trajectory
tracking in the presence of external disturbances. A cascaded control
architecture is designed to determine the desired accelerations using the
proposed controller and subsequently used to compute the desired orientation
and angular rates. The finite-time convergence of sliding functions and
closed-loop system stability are analytically proven. Furthermore, the
restrictive assumption on the maximum variation of the disturbance is relaxed
by designing a gain adaptation law and low-pass filtering of the estimated
equivalent control. The proper selection of design parameters is discussed in
detail. Finally, the effectiveness of the proposed method is evaluated by
high-fidelity software-in-the-loop simulations and validated by experimental
studies.
