Indirect altitude control of an unmanned aerial vehicle during the landing phase

Based on the Lyapunov stability criterion, a novel backstepping controller is developed to control the altitude and flight path angle of an unmanned aerial vehicle (UAV) throughout the landing stage. Landing path is divided in two stages: firstly UAV follows a straight line (glide-slope) and then it tracks an exponential curve (flare) to touch the ground. This flight path is employed as a reference trajectory to be tracked. To simulate the UAV dynamics, linearized equations of the longitudinal motion of an aircraft are employed. Moreover, disturbance is introduced to the model according to the Dryden wind turbulence model. To ensure the robustness and efficiency of the proposed controller a set of simulations are performed using the commercial software Matlab/Simulink. Simulation results reveal that the proposed controller successfully tracks the reference trajectory and finally tracking errors converge to zero.

Keywords:

automatic landing , backstepping control , wind turbulence