Nonsingular Fast Terminal Sliding Mode Attitude Control for a Quadrotor Based on Fuzzy Extended State Observer

During the flight, the quadrotor system is always subjected to unknown external disturbances. This paper investigates the design of a robust control scheme based on the nonsingular fast terminal sliding mode control (NFTSMC) technique and fuzzy extended state observer (FESO). First, a novel fuzzy extended state observer is designed to cope with unknown lumped disturbances, and the gain of the observer is adjusted by the fuzzy system to improve the estimation performance in an intelligent way. By using the estimation information of FESO, a new controller is proposed with NFTSMC algorithm to ensure that the quadrotor system can quickly track the desired attitudes, and tracking error converges to zero in a finite time. Finally, a comparative simulation experiment shows that the proposed control strategy can improve control performance and increase the robustness against disturbances effectively.