4D Trajectory Generation and Tracking for Waypoint-Based Aerial Navigation

One of the operational requirements for unmanned aerial vehicles is the autonomous navigation and control along a given sequence of waypoints, or along a predefined trajectory. Existing autonomous navigation procedures are mostly done in 3D because of the stringent certification requirements for 4D flight and due to the complexity in coping with time of arrival at waypoints, whilst actual flight plan fulfillment requires 4D navigation. The present paper deals with the 4D navigation trajectory generation and tracking of unmanned aerial vehicles along given sequences of waypoints with arrival time constraints at each of these waypoints. The approach that is used is twofold, first an optimal continuous trajectory is generated passing through the sequence of waypoints using the pseudospectral based trajectory optimization method, and then a predictive control law is used to drive the aircraft along the generated trajectory with minimum deviation. The proposed method for trajectory generation does not require slack variables to deal with the waypoints nor does it resort to the flight dynamics equations; thus the complexity of the underlying computation procedure is qualitatively lower than currently used methods. The method is successfully validated on two realistic cases giving better results than other conventional methods used in waypoint-based trajectory generation. Key-Words: Trajectory optimization, waypoint navigation, 4D trajectory, pseudospectral approximation, predictive control.