Advanced four-dimensional trajectory generation for tactical guidance of unmanned aerial vehicles

Abstract

A strategy is presented for the real-time generation of tactical, dynamically feasible 4D trajectories. The current framework for automatic flight control is analysed, along with current research into autonomous unmanned systems, to develop a technique for trajectory generation that not only works efficiently in the current architecture but also enhances the capabilities. The algorithm is based on a segmented trajectory constructed using quartic, i.e. 4ᵗʰ order, Pythagorean Hodograph (PH) curves based on Bézier splines. This yields nonic spatial curves, joined so as to ensure second order geometric (G²) continuity. The spatial trajectory is speci fied using way-points, tangents, and a geometric acceleration vector that controls the curvature. A velocity pro le is constructed to add the time component, which can be speci fied as a time of arrival or velocity at each way-point. Additionally the tangent, consisting of a heading and climb angle, can be specifi ed or calculated automatically. The primary contribution of this study is extending the algorithm to include all the orientational information, thus including the roll angle of the craft in the Pythagorean Hodograph (PH) curve construction. The demonstration of a basic aircraft performance model (APM) serves to illustrate the used of dynamic non-linear constraints, allowing for improved utilisation of the flight envelope. The computational advantages of using splines is shown by presenting an extensive collection of performance metrics to analyse the trajectory's efficiency and mission performance. The inclusion of the orientational dynamics allows for a more detailed analysis of the aircraft's aerodynamic performance. Using the results of the trajectory evaluation it is possible to apply kinodynamic constraints to ensure that the trajectory is within the aircraft's flight envelope.