Design of Adaptive Nonlinear Guidance Law for Unpowered UAV Tracking a Gliding Line

For tracking a given trajectory when UAV lost power, this paper presents a method of nonlinear adaptive guidance for following a line. Firstly, according to the geometric relationship, longitudinal and lateral guidance laws are designed and their stabilities are proved. Secondly, considering the significant influence between longitudinal and lateral laws as well as promoting the tracking accuracy and the anti-wind ability, the guidance laws are transformed into the two-order viscous systems with damping and oscillation and then the adaptive schemes are designed in order to improve the convergence of the oscillating system. Finally simulation results show that the proposed method increases tracking accuracy, despite being constantly subjected to wind disturbance.