Robust trajectory-tracking method for UAV guidance using proportional navigation

A guidance and control system for a trajectory-tracking unmanned aerial vehicle (UAV) is introduced. A proportional navigation guidance law is applied to a trajectory-tracking flight instead of using a traditional tracking-error correction based method. The system employs a dynamic inversion technique for the guidance force generation, which allows the UAV to maintain high maneuverability, and a simple velocity control to obtain a desired velocity. A trajectory is provided with a cubic-spline interpolation of given waypoints in order to simplify the trajectory making process. Using the cubic-spline function along to the trajectory arc, virtual target-points for the proportional navigation are easily obtained by using a flight distance instead of the trajectory arc. With the proportional navigation guidance, UAV may avoid its control saturation or divergence even in large tracking-error situations. Simulation results show that the system with the proportional navigation guidance has more robustness for trajectory-tracking than in the case of using the tracking-error correction based method.