Three-dimensional path tracking guidance and control for unmanned aerial vehicle based on back-stepping and nonlinear dynamic inversion

In order to realize the three-dimensional path tracking guidance and control for unmanned aerial vehicle (UAV), a new path tracking guidance and control method is presented, which separates the vehicle guidance and control problems into an outer guidance loop and an inner control loop. In outer guidance loop, the problem of tracking reference path is transformed to the tracking of a virtual vehicle by using a virtual vehicle which moves along the reference path for the real aircraft to track. A nonlinear guidance law is proposed based on the back-stepping method. In inner control loop, the flight control is designed based on the nonlinear dynamic inversion (NDI) theory and the time scale separation (TSS). The flight control can follow the commands generated by the outer guidance loop fleetly and accurately, which includes maneuver command generator, angle calculator, slow loop attitude angles control and fast loop attitude angle rate control. The stability of system is proved based on Lyapunov stability theory. Six degrees of freedom (6-DOF) simulation results illustrate that UAV can track three-dimensional path accurately, and demonstrate the feasibility and reasonability of the proposed method.