Robust Adaptive Backstepping Controller Design for Aircraft Autonomous Short Landing in the Presence of Uncertain Aerodynamics

To achieve tracking performance and robustness simultaneously during an aircraft’s autonomous short landing phase, a three-dimensional automatic landing system designed using robust adaptive backstepping control is investigated to direct aircraft glide-slope and flare maneuvers. To avoid the difficulty of analytically calculating the virtual command derivatives, a series of virtual command filters are introduced. By confining the input of the command filter, the flight states are subject to the landing constraints. To guarantee tracking performance in the presence of input and state constraints, antiwindup compensators are constructed by the saturation errors. To approximate the compound uncertainty brought by the ground effect and aerodynamic uncertainties, nonlinear disturbance observers are employed to estimate the uncertainties within a finite time. Synthesized with backstepping and adaptive proportional-integral-derivative control, the automatic landing control law is designed. Stability analysis shows that the closed-loop system achieves ultimately asymptotically bounded stability under weak uncertainties. Numerical simulations of autonomous landing demonstrate that the proposed control law can achieve both landing trajectory capturing performance and robustness against uncertain aerodynamics.