Composite Adaptive Attitude Control of Quadrotors

This paper presents a composite adaptive control (CAC) design for stabilizing the quadrotor's attitude under the strctured/unstructured uncertainties. In particular, the composite update law is constructed via the invariance (I&I) update method incorporated with the sigma modification to improve the transient behaviors and enhancing the robustness simultaneously. To that end, the so-called adding an integrator technique is included for avoiding the differentiation of the torque input vector involved in the standard I&I method. Next, a set of low-pass filters are introduced for preventing the differentiation of the virtual controllers. The proposed design ensures the boundedness of all the closed-loop signals and the ultimate convergence of the attitude tracking errors to the vicinity of zero. Simulation works are presented to demonstrate the validity of the proposed designs.