Design of σ-mod CMRAC algorithm for fixed-wing UAV

In this paper, we present a new model reference adaptive control (MRAC) for flight control system of unmanned aerial vehicle (UAV) with uncertainties. The beginning of new algorithm design is combining direct MRAC with indirect adaptive control, which is called composite model reference adaptive control (CMRAC). In the indirect part, we use a reverse filter to filter the system input. Then, we employ σ-modification to improve robustness of the flight control system. CMRAC with this kind of modification results in better tracking performance in the presence of parameter uncertainties and rapidly changing command input. Stability of the closed-loop system is formally proven by using Lyapunov theory. The effectiveness of the proposed algorithm is also illustrated through some simulations about the longitudinal dynamics of UAV.