Attitude control under wide-envelope for flying-wing UAVs combining tracking differentiator and incremental nonlinear dynamic inversion

To meet the requirements of a complete flight mission profile for the flying-wing Unmanned Aerial Vehicles (UAVs), autonomous and reliable attitude control under wide flying envelope plays a crucial role. How to overcome the influence of flying-wing UAVs’ insufficient longitudinal maneuverability, weak directional stability, as well as the combined effects of strong nonlinearity under wide operating conditions and external disturbances, to achieve precise and stable control, is a significant challenge. This paper focuses on the study of autonomous and reliable attitude control of flying-wing UAVs under wide flying envelope. Firstly, to overcome the effects of strong nonlinearity and model deviations of the aircraft, an Incremental Nonlinear Dynamic Inversion (INDI)-based attitude control method is designed. Combined with the dynamical characteristics of coordinated turns for vehicles, reasonable calculation of pseudo commands is achieved. Based on the proposed method, extensive simulation tests for longitudinal, lateral-direction channels and crosswind disturbances environments were carried out, to verify the effectiveness and limitations of the method. Secondly, to address the differential calculation problem in INDI, a Tracking Differentiator (TD)-based pseudo-command optimization method was designed. Finally, simulation and actual flight experiments of the attitude controller based on combining INDI and TD were conducted, and the advantages of the designed method were validated through tests in noise environments.