Assessing the Robustness of a UAS Detect & Avoid Algorithm

International audienceIn this article, we evaluate the robustness of a detect and avoid algorithm designed for the integration of UASs in terminal control areas. This assessment relies on a realistic modeling of navigation accuracy on positions and velocities and was carried out on thousands of scenarios built from recorded commercial traffic trajectories. The tested scenarios involved two different types of UASs – flying at 80 kts and 160 kts – with various missions, and three strategies for separation: one focussing on the separation distance, one focussing on the UAS mission and and combination of both. Fast-time simulation was used to evaluate each scenario against a wide range of accuracy levels corresponding to required navigation precision standards and linked to on-board navigation and communication systems. Experiments reveal a strong robustness of the separation algorithm up to relatively high uncertainty levels, indicating that UASs equipped with low accuracy navigation systems can still manage proper separation. However, the maneuvering cost for separation increases when the accuracy deteriorates. Nevertheless, a UAS with GPS-based navigation in a collaborative environment (e.g. aircraft providing their navigation parameters through ADS-B) can expect robustness at a reasonable cost

Receding horizon control for free-flight path optimisation

This paper presents a Receding Horizon Control (RHC) algorithm to the problem of on-line flight path optimization for aircraft in a Free Flight (FF) environment. The motivation to introduce the concept of RHC is to improve the robust performance of solutions in a dynamic and uncertain environment, and also to satisfy the restrictive time limit to the real-time optimization of this complicated air traffic control problem. Firstly, the mathematical model for the on-line FF path optimization problem is set up and discussed. Then, the proposed RHC algorithm is described in details. Simulation results illustrate that the new algorithm is very efficient and promising for practical applications. While achieving almost the same optimal solution as an existing algorithm in the absence of environmental uncertainties, it works better in a dynamic and uncertain environment. In either case, the online computational time of the proposed RHC algorithm is only a fraction of that of the existing algorithm

Optimisation de graphes sous contrainte géométrique : création d'un réseau de routes aériennes pour un contrôle Sector-Less

Alors que le système de gestion du trafic aérien arrive à saturation, de nouveauxconcepts sont étudiés afin de trouver une alternative. Cette thèse s'applique à vérifier la validité d'un de ces nouveaux concepts, le concept Sector-Less qui envisage un contrôle des aéronefs par flux, c'est-à-dire depuis leur aéroport de départ jusqu'à leur aéroport d'arrivée, par opposition au contrôle actuel effectué par zone géographique. La validation est faite à travers la construction et la validation d'un réseau de routes aériennes adapté à ce concept. La définition de ce nouveau réseau est donnée uniquement en fonction des contraintes imposées par le concept Sector-Less, sans utiliser de base préexistante. Ce réseau initial de routes est optimisé par deux méta-heuristiques différentes, recuit simulé et algorithme génétique. Le processus d'optimisation vise à minimiser la longueur de la trajectoire pour chaque flux d'aéronefs. Il intègre en particulier des algorithmes dynamiques de calcul des plus courts chemins dans un graphe. Pour prendre en compte les capacités de navigation des aéronefs, deux techniques ont été utilisées pour intégrer au processus d'optimisation des contraintes géométriques. La première technique consiste à exprimer les contraintes géométriques directement à travers la structure du graphe et à utiliser les algorithmes classiques pour calculer les plus courts chemins. La seconde est basée sur un nouvel algorithme permettant, sans altérer le graphe, de calculer une approximation des plus courts chemins. Le réseau de routes ainsi construit est testé du point de vue gestion du trafic aérien en simulant, à l'aide d'un simulateur de trafic en temps discret, le trafic dans l'espace aérien européen sur une journée complète. L'évaluation estime en particulier la charge de travail des contrôleurs aériens. L'analyse des résultats montre que le concept Sector-Less, tel qu'il est actuellement proposé, ne peut pas ˆetre mis en oeuvre. ABSTRACT : Taking into consideration the fact that the current air traffic management system is becoming saturated, new concepts are being developed in order to find an alternative. The aim of this thesis is to verify the validity of one of these new concepts, the Sector-Less concept, which envisages the control of aircraft from their departure to their destination as opposed to the current control which is done geographically. The process of validation is performed by constructing and validating an air route network adapted to this concept. The definition of this new network is designed from scratch, according to constraints imposed by the Sector-Less concept, without using any preexisting network. This initial route network is optimised using two different meta-heuristic, a simulated annealing algorithm and a genetic algorithm. The optimisation process tends to minimise the length of the trajectory of each flow. It integrates a graph dynamic shortest paths algorithm. Taking into account the aircraft navigation capacities, two techniques have been used in order to integrate geometric constraints with the optimisation process. The first technique consists of expressing geometric constraints directly through the graph structure and to use classic dynamic shortest paths algorithms. The second one is based on a new algorithm allowing, without altering the graph, to calculate an approximation of the shortest path. The route network constructed in this way is tested from an air traffic management point of view in simulating, using a discreet time air traffic simulator, European air trafic in the course of one day. The evaluation estimates in particular the workload of the air traffic controllers. The analysis of the results show that the Sector-Less concept, as it is currently proposed, cannot be put into effect