Robust path following controller for unmanned aerial vehicle based on carrot chasing guidance law using dynamic inversion

This paper focuses on autonomous path-following flight under uncertainty and external disturbances. Integrated UAV waypoints guidance scheme based on carrot chasing guidance law is presented. In order to follow a desired path a Virtual Track Point (VTP) is introduced on the path and make the UAV chase it. The UAV updates its heading direction toward the VTP. As time progresses, the UAV will move toward the path and asymptotically follow the path. Nonlinear Dynamic Inversion (NDI) awards the flight control system researchers a straight forward method of deriving control laws for nonlinear systems. The control inputs are used to cancel unwanted terms in the equations of motion using negative feedback of these terms. The two-timescale assumption that separates the fast dynamics which are the three angular rates of the aircraft from the slow dynamics which include the angle of attack, side-slip angle, and bank angle is adopted. NDI control law is designed for the fast variables using the deflection of aerodynamic control surfaces as inputs. Next, NDI is applied to the control of the slow states using the outputs of the fast loop as inputs. Simulation results for the nonlinear flight control system are given to illustrate the effectiveness of the technique. The validation of the designed flight system controller is demonstrated through real flight test.