Attitude control for fly wing unmanned aerial vehicle with input constraints

Considering the coupling between the rigid motion and the elastic motion in the dynamic model of an unmanned aerial vehicle with high-aspect-ratio fly wing configuration, we investigate its attitude control under input constraints, and propose a backstepping sliding-mode control method by employing the extended state observer. The extended state observer estimates effects of the aeroelastic mode and unknown disturbance in realtime. A tracking differentiator is introduced to alleviate the term explosion in the control law. According to the allocation of multiple control surfaces in the aerial vehicle with high-aspect-ratio fly wing configuration and the input constraints, we put forward an online allocation algorithm for the allocation of control surfaces, based on the linear-matrix-inequality (LMI). An auxiliary compensator is applied to provide compensation for the control command with time-delay due to the filter and input constraints. Applying Lyapunov stability theorem, we prove that the attitude tracking error will converge to a bounded value. Simulation results show that good performances in attitude tracking control are achieved when disturbances and constraints exist.