Lateral and longitudinal guidance and control design of a UAV in auto landing phase

In this paper, lateral and longitudinal guidance and control laws are proposed and implemented for autolanding phase of a UAV upto the touch down point. For lateral guidance, non-linear guidance logic has been used. Controllers design has been carried out based on the linearized dynamics of the aircraft. Glide slope control consists of speed control and off-glide slope distance control in the pitch axis. A new nonlinear control law in the pitch axis has been devised and its performance compared with the linear PID controller. In this way a glide slope is maintained up to the flare maneuver. In flare, the aircraft controls its height while height command exponentially decays to zero AGL. Controllers are designed for stability margins such that they show robustness against modeling deficiencies or any disturbance due to turbulence or gust wind. It is verified through simulations in a nonlinear environment that proposed guidance and control laws can be successfully applied to the practical autolanding of a UAV.