EP2178065A1 - Device for calculating an aircraft flight plan - Google Patents

Abstract

The device has a zone calculating unit (104) calculating zones reachable by an aircraft and their evolution over time based on position of the aircraft, data describing regulated zones prohibited to navigation, a digital terrain model, a list of movable and fixed obstacles and calculated prohibited zones. A selecting unit (105) selects a joining point of an initial flight plan situated in the reachable zone. A flight plan calculating unit (106) calculates the flight plan joined with the selected joining point.

Description

The invention relates to the navigation of an aircraft whose flight plan is subject to flight constraints and, more particularly, the calculation of a flight plan respecting these constraints.

An aircraft in flight is subject to various constraints affecting its navigation and more particularly impacting its flight plan. These constraints are, for example, obstacles, reliefs, restricted areas, other aircraft. Various systems have been developed to help a crew develop a flight plan that meets some of these flight constraints.

• ■ Navigation LOCNAV pour effectuer la localisation optimale de l'aéronef en fonction de moyens de géolocalisation (GPS, GALILEO, balises radios VHF, centrales inertielles) ;
• ■ Plan de vol FPLN pour saisir des éléments géographiques constituant le squelette de la route à suivre (procédures de départ et d'arrivée, points de passages (waypoints), airways) ;
• ■ Base de donnée de navigation NAVDB pour construire des routes géographiques et des procédures à partir de données incluses dans des bases (points, balises, legs d'interception ou d'altitude...) ;
• ■ Base de données de performance, PRF DB contenant les paramètres aérodynamiques et moteurs de l'appareil.
• ■ Trajectoire latérale TRAJ : pour construire une trajectoire continue à partir des points du plan de vol, respectant les performances avion et les contraintes de confinement (RNP) ;
• ■ Prédictions PRED : pour construire un profil vertical optimisé sur la trajectoire latérale ;
• ■ Guidage, GUID, pour guider dans les plans latéraux et verticaux l'aéronef sur sa trajectoire 3D, tout en optimisant la vitesse ;
• ■ Liaison de donnée numérique DATALINK, pour communiquer avec les centres de contrôle et les autres aéronefs.

Among these devices, flight management systems, known as FMS (acronym for the English expression Flight Management System), are known, comprising the following functions:

• ■ LOCNAV navigation to perform the optimal location of the aircraft according to geolocation means (GPS, GALILEO, VHF radio beacons, inertial units);
• ■ FPLN flight plan to capture geographic features that make up the skeleton of the route to be followed (departure and arrival procedures, waypoints, airways);
• ■ NAVDB navigation database to build geographic routes and procedures from data included in bases (points, tags, interception or altitude legacy ...);
• ■ Performance database, DB PRF containing the aerodynamic and engine parameters of the aircraft.
• ■ TRAJ lateral trajectory: to build a continuous trajectory from the points of the flight plan, respecting airplane performance and confinement constraints (RNP);
• ■ PRED predictions: to build an optimized vertical profile on the lateral trajectory;
• ■ Guidance, GUID, to guide the aircraft in its 3D trajectory in the lateral and vertical planes, while optimizing speed;
• ■ DATALINK digital data link, to communicate with control centers and other aircraft.

The functions accessible via an FMS, in particular for the creation of a flight plan, are insufficient to ensure the respect of all the flight constraints. Indeed, the function of creation of a flight plan does not verify the intersection of the proposed trajectory with the elements surrounding the aircraft (relief, zones, other aircraft, ...). In addition, the FMS does not have a digital terrain model to perform interference calculations of the predicted trajectory with terrain. An FMS also does not have the ability to detect surrounding aircraft or nearby weather events.

Also known systems ISS (acronym for the English expression Integrated Surveillance System) where its independent modules TAWS / TCAS / WXR perform a primary function of monitoring collision avoidance (called "Safety Net") with the ground and have for aiming for sound alerts during an exceptional terrain approach that allows the crew to react by engaging a vertical resource before it is too late.

To do this, the TAWS systems, decoupled from navigation systems, periodically compare the theoretical trajectory that the aircraft would describe during a resource and compare it to a section of the terrain overflown obtained from an onboard global digital terrain model. on board the calculator.

The availability of a terrain model allows secondary functions to improve the perception of the situation of the crew ("Situation Awareness"). Among them, the THD ("Terrain Hazard Display") aims to represent the vertical margins relating to the altitude of the aircraft by slices of false colors presented on the navigation screen. Class A TAWS, which are mandatory for commercial transport aircraft, generally have a simplified cartographic mode at a few hypsometric sections, making it possible to have a representation of the terrain during cruising flight phases.

Representations in false colors are currently limited by the ARINC-453 display standards (WXR type) and by the certification constraints which lead to deliberately degrading the resolution of the graphic representations proposed so as not to allow their use for navigation, incompatible with the certification level defined for a TAWS.

The functions performed by an ISS are insufficient to ensure compliance with all flight constraints. In fact, the resolution of digital terrain models of the order of 15 arc seconds (or less) is too high compared to the operating margins required for the situations envisaged and in fact not certifiable for navigation functions. In addition, the interfaces do not provide access to navigation data or the performance model to make predictions of vertical profile, flight time, and required fuel consumption. Finally, the interfaces do not allow to develop a flight plan nor to follow up via the guidance system.

Finally, we know the systems WUS (acronym for the English expression Weather Uplink System) which are devices allowing a communication of data between an aircraft and a ground device to load on board the aircraft dynamically and in real time all meteorological information that corresponds to the current and future evolution zone of the aircraft.

On the ground, this system is responsible for retrieving meteorological data from multiple sources (radar, surveys, predictions, satellites, ...) and providing the means of communication to establish a data link with an aircraft.

On board the aircraft, this system is in charge of establishing the link with the ground device, retrieving the data and making them available to the crew (graphically) or other equipment in order to exploit them at flight management or avoidance of potentially dangerous areas.

The functions performed by a WUS are insufficient to achieve the objectives of innovation. Indeed, the WUS does not have a numerical model of ground allowing to carry out the calculations of interference of the predicted trajectory with the relief nor of the capacity of detection of the surrounding aircraft or the close weather phenomena. In addition, the interfaces do not provide access to navigation data or the performance model to make predictions of vertical profile, flight time and required fuel consumption. Finally, the interfaces do not allow to develop a flight plan nor to follow up via the guidance system.

None of these equipment makes it possible to develop a flight plan providing sufficient safety margins for a period of a few minutes vis-à-vis all the constraints of flight that may occur in a given area: obstacles, reliefs, areas regulated, collaborative aircraft or not.

The invention aims in particular to overcome the problems mentioned above by proposing an onboard device on board an aircraft capable of automatically proposing a revision of the flight plan followed in order to avoid, with sufficient safety margins and over a time horizon of a few minutes, all the fixed obstructions (relief, obstacles, restricted areas) and mobile obstructions (aircraft, weather phenomena) close to the aircraft.

• ■ la détermination de paramètres caractérisant les mobiles détectés à partir de données provenant des capteurs pour la détection d'aéronefs environnants,
• ■ la détermination de paramètres caractérisant les phénomènes météorologiques détectés, à partir de données météorologiques provenant des capteurs météo,
• ■ le calcul de zones interdites et de leur évolution dans le temps à partir des paramètres caractérisant les aéronefs et les phénomènes météorologiques détectés, lesdites zones définissant un espace où l'aéronef ne peut pas voler,
• ■ le calcul de zones atteignables par l'aéronef et de leur évolution dans le temps à partir de la position de l'aéronef, de données décrivant des zones réglementées interdites à la navigation, d'un modèle numérique de terrain, d'une liste d'obstacles et des zones interdites calculées,
• ■ la sélection d'un point de rejointe du plan de vol initial situé dans une zone atteignable,
• ■ le calcul d'un plan de vol de rejointe vers le point de rejointe sélectionné.

For this purpose, the subject of the invention is a device for calculating a flight plan of an aircraft, said flight plan enabling rejoining to an initial flight plan, said aircraft comprising sensors for the detection of mobiles. and weather sensors for detecting meteorological phenomena, said device being characterized in that it comprises means for:

• The determination of parameters characterizing the mobiles detected from data coming from the sensors for the detection of surrounding aircraft,
• ■ the determination of parameters characterizing the meteorological phenomena detected, from meteorological data coming from the weather sensors,
• ■ the calculation of forbidden zones and their evolution over time based on the parameters characterizing the aircraft and the meteorological phenomena detected, said zones defining a space where the aircraft can not fly,
• ■ the calculation of areas achievable by the aircraft and their evolution over time from the position of the aircraft, data describing prohibited restricted areas to navigation, a digital terrain model, a list obstacles and calculated prohibited areas,
• ■ the selection of a joining point of the initial flight plan located in a reachable area,
• ■ calculating a joining flight plan to the selected joining point.

According to one characteristic of the invention, the calculation of the rejoin flight plan is iterated at regular intervals, a flight plan being evaluated according to a quality criterion; a joined flight plan calculated at a given iteration, known as a new flight plan, becomes the flight plan followed by the aircraft if a joined flight plan, calculated at a previous iteration and followed by the aircraft, current flight, presents an evaluation, within the meaning of the quality criterion, whose difference with the evaluation of the new calculated flight plan is greater than a given threshold.

According to a characteristic of the invention, the calculation of reachable areas comprises an estimation of the distances of the points in a map obtained by projection on a horizontal plane of a 3D representation of an evolution space by a mesh of elementary cubes associated with levels of danger and identified by an altitude, a latitude, a longitude and a date, said estimate consisting in applying a distance transform, the cubes associated with danger levels higher than a permissible value N _l identifying the prohibited areas for l 'aircraft; said distance transform estimating the distances of the different points of the image with respect to a source point representing the position of the aircraft by applying, by scanning, a mask at the different points of the image; a determined initial distance value being assigned, at the start of scanning, to all the points of the image except at the source point, the origin of the distance measurements, which is assigned a value of zero distance.

• ■ lire la distance estimée D_V du point voisin P_V,
• ■ lire un coefficient C_XY du masque correspondant à la case occupée par le point voisin P_V,
• ■ calculer une distance propagée D_P correspondant à la somme de la distance estimée D_V du point voisin P_V et du coefficient C_XY affecté à la case du masque occupée par le point voisin P_V: $$D_P=D_V+C_{\mathit{XY}},$$
  
• ■ calculer une altitude prévisible Ap de l'aéronef après franchissement de la distance D_P,
• ■ calculer une date propagée Tp à la position après franchissement de la distance D_P,
• ■ lire un niveau de danger N_i,j,Ap,Tp prévisible du point but P_i,j dans la représentation en cubes élémentaires de l'espace aérien à l'altitude prévisible A_P et à date propagée Tp,
• ■ comparer le niveau de danger prévisible N_¡,j,Ap,Tp à une valeur limite autorisée N_l pour le vol, augmentée d'une marge de sécurité Δ,
• ■ éliminer la distance propagée D_P si le niveau de danger prévisible N_i,j,Ap,Tp est supérieur à celui admissible pour le vol majoré par la marge de sécurité Δ,
• ■ si le niveau de danger prévisible N_i,j,Ap,Tp majoré par la marge de sécurité Δ, est inférieur à la limite N_l fixée pour le vol, lire la distance D_i,j déjà affectée au point but considéré P_i,j et la comparer à la distance propagée D_P (étape 99),
• ■ éliminer la distance propagée D_P si elle est supérieure ou égale à la distance D_i,_j déjà affectée au point but considéré P_i,j, et
• ■ remplacer la distance D_i,j déjà affectée au point but considéré P_i,j, par la distance propagée D_P si cette dernière est inférieure.
• ■ les cubes élémentaires présentant une distance inférieure à la plus grande distance mesurable sur l'image à la fin du balayage, étant désignés zone atteignables.

According to one characteristic of the invention, the estimate of the distance of the source point to a considered point P _{i, j} , said goal point, being placed in a determined cell of the mask, consists for each neighboring point P _V entering the cells of the mask and whose distance has already been estimated during the same scan to:

• ■ read the estimated distance D _V from the neighboring point P _V ,
• ■ read a coefficient C _XY of the mask corresponding to the square occupied by the neighboring point P _V ,
• ■ calculate a propagated distance D _P corresponding to the sum of the estimated distance D _V of the neighbor point P _V and the coefficient C _XY assigned to the mask space occupied by the neighboring point P _V : $$D_P=D_V+{\mathrm{VS}}_{\mathit{XY}},$$
  
• ■ calculate a predictable altitude Ap of the aircraft after crossing the distance D _P ,
• ■ calculate a propagated date Tp at the position after crossing the distance D _P ,
• ■ read a predictable level of danger N _{i, j, Ap, Tp} of the goal point P _{i, j} in the representation in elementary cubes of the airspace at the predictable altitude A _P and propagated date Tp,
• Compare the expected level of danger N _{¡, j, Ap, Tp} to an authorized limit value N _l for the flight, increased by a safety margin Δ,
• ■ eliminate the propagated distance D _P if the foreseeable danger level N _{i, j, Ap, Tp} is greater than that allowed for the flight plus the safety margin Δ,
• ■ if the foreseeable level of danger N _{i, j, Ap, Tp} plus the safety margin Δ, is lower than the limit N _l fixed for the flight, read the distance D _{i, j} already affected at the point of interest considered P _{i , j} and compare it to the propagated distance D _P (step 99),
• ■ eliminate the propagated distance D _P if it is greater than or equal to the distance D _i , _j already assigned to the considered goal point P _{i, j} , and
• ■ replace the distance D _{i, j} already assigned to the point of interest considered P _{i, j} , by the propagated distance D _P if the latter is lower.
• ■ the elementary cubes having a distance smaller than the greatest distance measurable on the image at the end of the scan, being designated zone reachable.

où Ci est une note attribuée selon un critère d'évaluation i,... et α_i est une valeur associée au critère d'évaluation i et reflétant son importance, i étant une valeur comprise entre 1 et 5.According to a characteristic of the invention, the selection of the rejoining point comprises the calculation of a note C for points of the initial flight plan located in an attainable zone, the rejoining point of the initial flight plan selected being that obtaining the best score C, said score being calculated according to the following relationship: $$\mathrm{VS}=\left[{\left({\displaystyle \underset{i=1}{\overset{\mathrm{not}}{\Pi }}}{\left(1+{\mathrm{VS}}_i\right)}^{{\alpha }_i}\right)}^{\frac{1}{{\displaystyle \underset{i)1}{\overset{\mathrm{not}}{\Sigma }}}{\alpha }_i}}-1\right]$$

where Ci is a score given according to an evaluation criterion i, ... and α _i is a value associated with the evaluation criterion i and reflecting its importance, i being a value between 1 and 5.

According to one characteristic of the invention, the parameters characterizing the detected mobiles comprise a speed, a position and a future flight plan.

According to one characteristic of the invention, the forbidden zone associated with a mobile characterized solely by its position is defined by a succession of concentric circles with rays obeying an increasing law as a function of time and whose center is the position of said mobile.

où p est l'intervalle de temps séparant les centres de deux cylindres successifs, r_i et r_i+1 représentent les rayons de deux cylindres successifs.According to one characteristic of the invention, the prohibited zone associated with a mobile characterized by its position and by its velocity vector is defined by a succession of cylinders whose centers correspond to the predicted position of said mobile from said velocity vector, said centers being spaced apart by a regular interval of time p, the radii of the successive cylinders obeying an increasing law as a function of time and respecting the following relation: $${\mathrm{r}}_{\mathrm{i}}\mathrm{+}{\mathrm{r}}_{\mathrm{i}\mathrm{+}\mathrm{1}}\mathrm{>}\mathrm{p}$$

where p is the time interval separating the centers of two successive cylinders, r _i and r _{i + 1} represent the radii of two successive cylinders.

According to one characteristic of the invention, the prohibited zone associated with a mobile characterized by its position and by its future flight plan is defined by a tube enveloping the flight plan.

According to one characteristic of the invention, the prohibited zone associated with a mobile characterized by its position and by its future flight plan is defined by a rectangular parallelepiped enveloping the flight plan.

• La figure 1 représente un exemple de réalisation du dispositif selon l'invention.
• La figure 2 représente les interfaces du dispositif selon l'invention.
• La figure 3 représente un exemple de phénomène météorologique caractérisé par des paramètres.
• La figure 4 illustre une zone interdite associée à un aéronef de type planeur.
• La figure 5 illustre une zone interdite associée à un mobile de type avion de transport caractérisé par un vecteur vitesse.
• La figure 6 illustre une zone interdite associée à un aéronef caractérisé par une trajectoire.
• La figure 7 représente un exemple de masque de chanfrein.
• Les figures 8a et 8b montrent les cellules du masque de chanfrein illustré à la figure 7, qui sont utilisées dans une passe de balayage selon l'ordre lexicographique et dans une passe de balayage selon l'ordre lexicographique inverse.
• La figure 9 illustre les principales étapes d'un traitement effectué pour déterminer les zones atteignables par l'aéronef en tenant compte de contraintes.
• La figure 10 illustre une trajectoire initiale et une trajectoire de rejointe.
• La figure 11a montre un exemple de notes attribuées à un plan de vol de rejointe en fonction du nombre de points de passage conservés par rapport à un plan de vol initial.
• La figure 11 b montre un exemple de notes attribuées à un plan de vol de rejointe en fonction d'une quantité de virage totale par rapport au plan de vol initial.
• La figure 11 c montre un exemple de notes attribuées à un plan de vol de rejointe en fonction du ratio entre la longueur de la trajectoire initiale et sa longueur.
• La figure 11d montre un exemple de notes attribuées à un plan de vol de rejointe en fonction de l'angle de rejointe de plan de vol.
• La figure 11 e montre un exemple de notes attribuées à un plan de vol de rejointe en fonction de la surface d'écart par rapport au plan de vol initial.
• Le dispositif selon l'invention peut être utilisé notamment pour:
  • ■ des aéronefs de transport civil afin de décharger le pilote d'une partie des actions ou de repenser ― sous certaines conditions - la répartition des rôles avec le contrôle aérien,
  • ■ des aéronefs de transport d'affaire ou d'aviation générale opérés dans des espaces aériens non contrôlés,
  • ■ des aéronefs militaires opérés dans des espaces aériens civils non contrôlées ou des espaces aériens tactiques ségrégés, dans lesquels opère un ensemble d'aéronefs potentiellement discrets et/ou hostiles.
• Le dispositif selon l'invention peut être utilisé pour calculer une trajectoire de rejointe d'un aéronef vers sa trajectoire initiale. Un tel dispositif peut aussi être utilisé pour modifier la trajectoire initiale de l'aéronef lorsqu'une nouvelle menace (un phénomène météorologique ou un mobile) est apparue. L'horizon temporel de détection et de reconfiguration de la route est de l'ordre de quelques minutes (2 par exemple), répondant aux besoins classiques de séparation pour des aéronefs évoluant dans des espaces aériens civils.
• L'élaboration d'un plan de vol assurant des marges de sécurité suffisantes pour une durée de quelques minutes vis à vis de l'ensemble des contraintes de vol pouvant se présenter pose notamment les problèmes suivants :
  • ■ la détection les mobiles environnants (aéronefs ou phénomènes météo),
  • ■ l'évaluation de leur type et le danger qu'ils représentent
  • ■ l'élaboration d'un plan de vol de reconfiguration assurant une séparation avec ces phénomènes et :
  • o tenant au mieux compte des contraintes du plan de vol initialement suivi,
  • o évitant les espaces aériens interdits ou réglementés,
  • o évitant le relief environnant avec des marges opérationnelles adhoc,

The invention will be better understood and other advantages will appear on reading the detailed description given by way of non-limiting example and with the aid of the figures among which:

• The figure 1 represents an embodiment of the device according to the invention.
• The figure 2 represents the interfaces of the device according to the invention.
• The figure 3 represents an example of a meteorological phenomenon characterized by parameters.
• The figure 4 illustrates a prohibited zone associated with a glider-type aircraft.
• The figure 5 illustrates a prohibited zone associated with a transport-type mobile characterized by a speed vector.
• The figure 6 illustrates a forbidden zone associated with an aircraft characterized by a trajectory.
• The figure 7 represents an example of a chamfer mask.
• The Figures 8a and 8b show the cells of the chamfer mask shown in the figure 7 , which are used in a scanning pass according to the lexicographic order and in a scanning pass in the inverse lexicographic order.
• The figure 9 illustrates the main steps of a processing performed to determine the areas achievable by the aircraft taking into account constraints.
• The figure 10 illustrates an initial trajectory and a joining trajectory.
• The figure 11a shows an example of notes assigned to a joined flight plan based on the number of waypoints retained in relation to an initial flight plan.
• The figure 11 b shows an example of notes assigned to a joined flight plan based on a total turnaround amount from the initial flight plan.
• The figure 11 c shows an example of notes assigned to a joined flight plan based on the ratio between the length of the initial trajectory and its length.
• The figure 11d shows an example of notes assigned to a joined flight plan based on the flight plan rejection angle.
• The figure 11 e shows an example of notes assigned to a joined flight plan based on the deviation area from the initial flight plan.
• The device according to the invention can be used in particular for:
  • ■ civil transport aircraft to unload the pilot from part of the actions or to rethink - under certain conditions - the division of roles with air traffic control,
  • ■ commercial or general aviation aircraft operating in uncontrolled airspace,
  • ■ military aircraft operated in uncontrolled civilian airspace or segregated tactical airspace, in which a range of potentially unobtrusive and / or hostile aircraft operate.
• The device according to the invention can be used to calculate a path of rejoining an aircraft towards its initial trajectory. Such a device can also be used to modify the initial trajectory of the aircraft when a new threat (a weather phenomenon or a mobile) has appeared. The time horizon of detection and reconfiguration of the road is of the order of a few minutes (2 for example), meeting the classic separation requirements for aircraft operating in civil airspace.
• The development of a flight plan providing sufficient safety margins for a period of a few minutes with respect to all the flight constraints that may arise poses the following problems:
  • ■ detection of surrounding mobiles (aircraft or weather phenomena),
  • ■ the assessment of their type and the danger they represent
  • ■ the development of a reconfiguration flight plan ensuring separation from these phenomena and:
  • o taking into account the constraints of the initial flight plan,
  • o avoiding prohibited or restricted airspace,
  • o avoiding the surrounding terrain with ad hoc operating margins,

When the separation can no longer be respected, the problem is then to develop an avoidance maneuver. We know, for example, by the French patent no. 2,893,146 , an embedded system on board an aircraft, for the prevention of ground collisions, of the TAWS type, providing assistance to the crew for determining an effective lateral avoidance course of the terrain in the event of a confirmed risk of collision with the ground.

• des dispositifs de localisation 201 fournissant la position de l'aéronef,
• une base de données 202 de zones aériennes réglementées ou restreintes. Cette base peut être mise à jour dynamiquement (activation de certaines zones réglementées ou restreintes, déplacement des phénomènes météorologiques, déplacement de zones interdites de survol pour les zones militaires tactiques, etc.),
• une base de données 203 d'élévations du terrain environnant et d'obstacles,
• un système de gestion de vol (ou flight management) 204 pour récupérer les données de plan de vol et lui communiquer le plan de vol de rejointe calculé,
• de capteurs de détection de mobiles environnants 205, et
• une liaison météorologique 206 ou weather uplink selon l'expression anglo-saxonne.

The figure 1 represents an embodiment of the device according to the invention. The figure 2 represents the interfaces of the device according to the invention. This device 100 comprises a calculation and processing module (CPU, memory, etc.). He communicates with:

• locating devices 201 providing the position of the aircraft,
• a database 202 of restricted or restricted airspace. This base can be dynamically updated (activation of certain restricted or restricted zones, movement of meteorological phenomena, displacement of no-fly zones for tactical military zones, etc.),
• a database of 203 elevations of the surrounding terrain and obstacles,
• a flight management system 204 for retrieving the flight plan data and communicating to it the calculated joined flight plan,
• sensors for sensing surrounding mobiles 205, and
• a weather link 206 or weather uplink according to the Anglo-Saxon expression.

The device according to the invention comprises means for determining parameters characterizing the detected aircraft 101 from data coming from the sensors for the detection of surrounding aircraft. The sensors that can be used for the detection of surrounding aircraft are, for example: a TCAS, a radar, an Optronics sensor, an infrared sensor or a data link (for example ADS-B or link 16). These data make it possible to consider aircraft detected near the aircraft, in the given time horizon (for example two minutes)

This module characterizes the dimensioning parameters of the aircraft detected by consolidating the data received from the various sensors.

The parameters characterizing a detected aircraft comprise: (i) a detected type of aircraft, (ii) a 3D reference position of the aircraft, (iii) a prediction of displacement of the aircraft in the form of a predicted 4D trajectory starting from the reference point and (iv) the consolidated detection means for developing the reference position and the prediction of the displacement of the aircraft, for example, a radar, a TCAS, an ADS-B collaboration, a data link received from the ground or from a control aircraft (of the 16-link type, for example), optronic, infra-red.

The characterization makes it possible to estimate the type of aircraft nearby and its future trajectory in order to be able to define the rules of the air, the margins and the applicable priorities.

• les priorités relatives des aéronefs, afin de déterminer quel aéronef doit effectuer une manoeuvre de séparation, du plus prioritaires (n'a pas à « bouger ») au moins prioritaire : ballon, planeur, avion,
• les manoeuvres à privilégier : par exemple, en situation d'approche :
  • une remise de gaz ; en croisière : un virage à droite pour doubler par
  • la droite.

Among the applicable rules, one can take into account, for example:

• the relative priorities of the aircraft, in order to determine which aircraft must perform a separation maneuver, of the highest priority (does not have to "move") at least priority: balloon, glider, airplane,
• maneuvers to favor: for example, in an approach situation:
  • a go-around cruising: a right turn to double by
  • the right.

• ■ Les ballons à air chaud, par exemple caractérisés par leur signature thermique (IR) et leur volume (optro) ;
• ■ Les planeurs, par exemple caractérisés par leur envergure et leur vitesse ;
• ■ Les avions d'aviation générale et hélicoptères, par exemple caractérisés par leur signature métallique (radar) et leur vitesse (radar doppler). Un hélicoptère évoluant à plus 70 noeuds n'est pas différent d'un avion d'aviation générale. Les avions de transport, par exemple caractérisés par leur signature métallique (radar), leur vitesse (radar doppler) et leur altitude d'évolution, en général plus élevée sauf à proximité des aéroports ;
• ■ Les aéronefs militaires véloces, par exemple essentiellement caractérisés par un couple vitesse d'évolution/altitude incompatible avec des opérations civiles (dans les zones tactiques/ségrégées) ou leur proximité avec une zone réglementée/réservée aux opérations militaires dans des missions de transport aérien civil ;

The types of aircraft envisaged are among:

• ■ Hot air balloons, for example characterized by their thermal signature (IR) and their volume (optro);
• ■ Gliders, for example, characterized by their size and speed;
• ■ General aviation and helicopter aircraft, for example characterized by their metallic signature (radar) and speed (Doppler radar). A helicopter operating at more than 70 knots is no different from a general aviation aircraft. Transport aircraft, for example characterized by their metallic signature (radar), their speed (Doppler radar) and their altitude of evolution, generally higher except near the airports;
• ■ Swift military aircraft, for example, mainly characterized by a speed / altitude pair that is incompatible with civilian operations (in tactical / segregated areas) or their proximity to a restricted / reserved area for military operations in air transport missions. civil;

• ■ Vecteur : la trajectoire de l'aéronef n'est connue que par le vecteur vitesse donnant un cap et une tendance verticale. Cette description issue de capteurs de type radar (ou optronique) aptes à élaborer une détection et une estimation de la vitesse de la « cible » mesurée est corrélée à la connaissance de l'évolution de l'aéronef embarquant le dispositif selon l'invention et permet d'estimer un vecteur vitesse 3D de chaque « cible ».
• ■ Plan de vol : la trajectoire de l'aéronef est connue par la description du chemin latéral prévu. Cette description est issue d'informations collaboratives, comme la transmission de quelques branches du plan de vol des aéronefs civils par ADS-B par exemple.
• ■ 3D : la trajectoire de l'aéronef est connue à la fois en latéral et en vertical. Cette description est issue d'informations collaboratives, par exemple via les transmissions de données de vol sur les aéronefs « amis » transmis par un centre de contrôle militaire.

The knowledge of the aircraft type is used to determine the necessary room for maneuver and priority rules to be applied. The types of trajectories envisaged are among:

• ■ Vector: the trajectory of the aircraft is only known by the speed vector giving a heading and a vertical trend. This description, derived from radar (or optronic) type sensors capable of developing a detection and an estimation of the speed of the measured "target", is correlated with the knowledge of the evolution of the aircraft carrying the device according to the invention and allows to estimate a 3D velocity vector of each "target".
• ■ Flight plan: the trajectory of the aircraft is known by the description of the planned lateral path. This description comes from collaborative information, such as the transmission of some branches of the flight plan of civil aircraft by ADS-B for example.
• ■ 3D: the trajectory of the aircraft is known both laterally and vertically. This description is derived from collaborative information, for example via the transmission of flight data on "friendly" aircraft transmitted by a military control center.

• ■ Dans le cadre d'une mission civile, les informations issues de systèmes collaboratifs (comme l'ADS-B) sont utilisées en priorité ;
• ■ Dans le cadre d'une mission militaire (discrète par exemple), les données transmises par un système de commandement sont privilégiées ;
• ■ Dans le cadre d'un vol civil hors des espaces aériens contrôlés, les données collectées par des systèmes actifs à bord de l'aéronef, par exemple de type radar ou TCAS sont privilégiés.

When multiple sources of information are available, selection rules can be used that define which sources of information are used in priority. For example :

• ■ As part of a civil mission, information from collaborative systems (such as ADS-B) is used as a priority;
• ■ In the context of a military mission (discrete for example), the data transmitted by a command system are privileged;
• ■ In the context of a civil flight outside controlled airspace, the data collected by active systems on board the aircraft, for example radar or TCAS type are preferred.

The device according to the invention comprises means for determining parameters characterizing the detected weather phenomena, 102 from meteorological data coming from the weather sensors. By consolidating various sources of meteorological information, for example, a WXR radar and a weather data link, it is estimated the type of phenomenon in the vicinity of the aircraft. The types of phenomena detected are among: the predicted windshear zones, the areas of turbulence, thunderstorms, storms and areas of volcanic eruptions (or eruptive dusts).

• ■ Un volume 301 et un point de référence 302, par exemple, sous la forme d'un cylindre,
• ■ Une trajectoire 4D ― 3D et temps - prédite du point de référence, par exemple, la trajectoire 303 centre du disque de base du cylindre C(t), en trois dimensions, altitude, latitude et longitude et en fonction du temps,
• ■ Des lois d'évolution temporelle du volume de référence, par exemple, l'évolution des dimensions du cylindre de base dans le temps avec R(t) pour le rayon 304 et H(t) pour la hauteur 305, où t est le temps.

The type of phenomenon makes it possible to define the rules of the air and the applicable margins. Meteorological phenomena are also defined by the following parameters illustrated in figure 3 :

• ■ A volume 301 and a reference point 302, for example, in the form of a cylinder,
• ■ A 4D - 3D trajectory and time - predicted reference point, for example, the center 303 trajectory of the C (t) cylinder base disk, in three dimensions, altitude, latitude and longitude and as a function of time,
• ■ Laws of temporal evolution of the reference volume, for example, the evolution of the dimensions of the base cylinder in time with R (t) for radius 304 and H (t) for height 305, where t is the time.

The volume parameter can be any three-dimensional volume (polyhedron, sphere, ...). The temporal evolution laws of the volume are then based, for example, on the vertices of the polyhedron.

The device according to the invention comprises means for calculating forbidden zones and their evolution over time 103 from the parameters characterizing the aircraft and the meteorological phenomena detected. Depending on the type of aircraft or weather phenomenon detected, it is possible to calculate lateral margins, vertical margins, an estimate of the deviation, an increase in the margins as a function of time and the confidence in the measurement and the estimated speed / direction.

The figure 4 illustrates a prohibited zone associated with a glider-type aircraft. The forbidden zone of a mobile whose speed vector is known only and whose velocity vector is not known is defined by a succession of concentric circles whose radii 402, 403 obey an increasing law as a function of time and whose center is the position 401 of said mobile. The trajectory associated with a glider not being predictable, the calculated forbidden zone forms a circle whose radius is increasing in time. This secure volume is defined by sampling. Samples i are made with a time step of p given, for example p = 10 seconds. The prohibited volume is represented by a restriction zone of r _i seconds around the initial position of the glider 401. The r _i are croissants, for example r ₁ = 5 seconds and r ₂ = 10 seconds and form concentric circles.

The figure 5 illustrates a prohibited zone associated with a transport aircraft type aircraft whose speed vector is known. This forbidden volume is defined by sampling. Samples i are made with a time step of p given, for example p = 10 seconds. The secure volume is represented by a restriction area of r _i seconds. The restriction zones rays meet the following formula: r _¡+ r _{i + 1>} p. In this way, the restriction zones partially overlap, while simplifying sampling and limiting the need for computing resources.

The table below represents the list of samples and the dates when the corresponding area is prohibited for use by the aircraft carrying a device according to the invention. Sample Sample date Restriction start date Restriction end date 1 10s 6 s 14s 2 20s 15s 25s 3 30s 24s 36 s

The figure 5 , corresponding to the previous table, illustrates the restriction zone at three different dates. All three samples are taken at 10-second intervals. The center of this zone is the predicted position of a detected aircraft calculated with the speed vector of said aircraft. A first point 501 represents the position of the aircraft at a date of 10 seconds. A second 502 and a third point 503 respectively represent the position of the aircraft at a date of 20 seconds and a date of 30 seconds.

The figure 6 illustrates a prohibited zone associated with an aircraft whose trajectory is known. For an aircraft whose trajectory in 3D is known, the forbidden zone is defined, for example, by: a tube enveloping a plane of flight provided on the horizontal plane 601 having a radius corresponding to a measurement 602 of the variation of the parameters on a given period, for example 15 seconds. The principle is to estimate the maximum deviation measured with respect to the flight plan in the near past, for example one minute. The deviation is measured laterally and vertically. We keep a certain percentage, for example 95%, of the maximum measured.

The forbidden zone can also be defined by a rectangular parallelepiped corresponding to a corridor around the horizontal trajectory and a fixed height margin around the vertical description of the 3D part. A rectangular parallelepiped makes it possible to estimate the lateral and vertical deviations independently, according to the same principle.

The device according to the invention comprises means for the calculation of zones, in four dimensions, reachable by the aircraft 104 from the position of the aircraft, data describing restricted zones prohibited to navigation, a model digital terrain, a list of obstacles and calculated prohibited areas. We already know in the patent application FR 2 910 640 an estimation method, for a mobile subject to constraints of vertical trajectory profile and risk minimization, of the distances of the points of a map obtained by projection on a horizontal plane of a 3D representation of a space of evolution by a mesh of elementary cubes associated with danger levels and identified by an altitude, a latitude and a longitude. However, this method does not take into account dynamic weather phenomena and mobiles whose position changes over time.

The means for the four-dimensional attainable zone calculation according to the invention satisfies, at each propagation step, in addition to the criteria described in the aforementioned application, if, for a given 3D position and a considered date, the aircraft is more than a certain distance (horizontal separation and vertical separation) of a mobile or weather phenomenon predicted on date t. The time step on mobile sampling and weather phenomena is expanded according to separation margins. For example, mobiles and weather phenomena are predicted in steps of 15 seconds.

The process described in the patent application FR 2 910 640 implements a distance transform operating by propagation on a 2D image of the map whose pixels arranged in rows and columns by orders of values of longitude and latitude correspond to the columns of cubes elementary of the mesh of the representation of the space of d and identify, for each column, forbidden altitude ranges corresponding to the cubes associated with danger levels higher than a permissible value for their crossing. This transform of distance estimates the distances of different points of the image from a source point placed near the mobile by applying, by scanning, a chamfer mask at different points of the image. The distance estimation of a point, by application of the chamfer mask at this point said goal point is carried out by listing the various paths from the point of the point of source to the point and passing through points of the neighborhood of the point of purpose that are covered by the chamfer mask and whose distances to the source point were previously estimated during the same scan, by determining the lengths of the different paths listed by summing the distance assigned to the neighborhood's crossing point and its distance to the extracted point of aim of the chamfer mask, looking for the shortest path among the listed paths and adopting its length as an estimate of the distance from the goal point. Initially, at the beginning of the scan, a distance value greater than the largest distance measurable on the image is attributed to all the points of the image except at the source point, the origin of the distance measurements, which is assigned a distance value. nothing. The lengths of the paths listed, when the chamfer mask is applied to a goal point, with a view to finding the shortest path, are translated into travel time for the mobile and the routes listed, including the travel times. for the mobile are such that it would reach the goal point in an elementary cube of the representation of the evolution space whose danger level is higher than a permissible value, are excluded from the search of the shortest path.

Remember that the distance between two points of a surface is the minimum length of all possible paths on the surface, starting from one of the points and ending in the other. In an image formed of pixels distributed according to a regular mesh of lines, columns and diagonals, a propagation distance transform estimates the distance of a pixel called "goal" pixel with respect to a so-called "source" pixel pixel by progressively building, starting from the source pixel, the shortest possible path following the mesh of the pixels and ending in the goal pixel, with the aid of the distances found for the pixels of the image already analyzed and a table called chamfer mask listing the values distances between a pixel and its close neighbors.

As shown in figure 7 , a chamfer mask is in the form of a table with a layout of boxes reproducing the pattern of a pixel surrounded by his close neighbors. In the center of the pattern, a box with a value of 0 marks the pixel taken as the origin of the distances listed in the table. Around this central box, agglomerate peripheral boxes filled with non-zero distance values and taking again the disposition of the pixels of the neighborhood of a pixel supposed to occupy the central box. The distance value in a peripheral box is that of the distance separating a pixel occupying the position of the relevant peripheral box from a pixel occupying the position of the central box. Note that the distance values are distributed in concentric circles. A first circle of four boxes corresponding to the four pixels closest to the pixel of the central box, placed either on the line or on the column of the pixel of the central box, are assigned a distance value D1. A second circle of four boxes corresponding to the four pixels closest to the pixel of the central box, placed outside the row and column of the pixel of the central box, are assigned a distance value D2. A third circle of eight boxes corresponding to the eight pixels closest to the pixel of the central box, placed outside the row, the column and the diagonals of the pixel of the central box, are assigned a value D3.

la valeur 7 qui est une approximation de $5\sqrt{2},$

et à la distance D3 la valeur 11 qui est une approximation de $5\sqrt{5}\mathrm{.}$

The chamfer mask can cover a more or less extended neighborhood of the pixel of the central square by listing the values of the distances of a greater or lesser number of concentric circles of pixels of the neighborhood. It can be reduced to the first two circles formed by the pixels of the neighborhood of a pixel occupying the central cell or be extended beyond the first three circles formed by the pixels of the neighborhood of the pixel of the central cell, but it is usual to stop at first three circles as is the case of the chamfer mask shown in figure 7 . The values of the distances D1, D2, D3 which correspond to Euclidean distances are expressed in a scale allowing the use of integers at the price of a certain approximation. Thus G. Borgefors gives the distance D1 corresponding to a step on the abscissa x or on the ordinate y the value 5, at the distance D2 corresponding to the root of the sum of the squares of the rungs on the abscissa and ordinate $\sqrt{x^2+{\mathrm{there}}^2}$

the value 7 which is a approximation of $5\sqrt{2},$

and at the distance D3 the value 11 which is an approximation of $5\sqrt{5}\mathrm{.}$

The gradual construction of the shortest possible path to a goal pixel, starting from a source pixel and following the pixel mesh is done by regular scanning of the pixels of the image by means of the chamfer mask. Initially, the pixels of the image are assigned an infinite distance value, in fact a sufficiently high number to exceed all the values of the measurable distances in the image, with the exception of the source pixel which is assigned a value of zero distance. Then the initial distance values assigned to the goal points are updated during the scanning of the image by the chamfer mask, an update consisting in replacing a distance value assigned to a goal point with a new lower value. resulting from a distance estimation made on the occasion of a new application of the chamfer mask at the point of interest considered.

A distance estimation by applying the chamfer mask to a goal pixel consists in listing all the paths going from this goal pixel to the source pixel and passing through a pixel of the neighborhood of the goal pixel whose distance has already been estimated during the same scan , to search among the listed routes, the shortest path (s) and to adopt the length of the shortest path (s) as the distance estimate. This is done by placing the goal pixel whose distance is to be estimated in the center box of the chamfer mask, by selecting the peripheral boxes of the chamfer mask corresponding to pixels of the neighborhood whose distance has just been updated, in calculating the lengths of the shortest paths connecting the pixel to be updated to the source pixel passing through one of the selected pixels of the neighborhood, by adding the distance value assigned to the pixel of the neighborhood concerned and the distance value given by the chamfer mask, and to adopt, as distance estimation, the minimum of the path length values obtained and the old distance value assigned to the pixel being analyzed.

The scanning order of the pixels in the image affects the reliability of the distance estimates and their updates because the paths taken into account depend on them. In fact, it is subject to a regularity constraint that if the pixels of the image are spotted according to the lexicographic order (pixels ranked in increasing order line by line starting from the top of the image and progressing down the image, and from left to right within a line), and if a pixel was analyzed before a pixel q then a pixel p + x must be analyzed before the pixel q + x. Lexicographic orders, inverse lexicography (scanning of the pixels of the image line by line from bottom to top and, within a line, from right to left), transposed lexicography (scanning of the pixels of the image column by column of left to right and, in a column, from top to bottom), inverse transposed lexicographic (scanning of pixels by columns from right to left and within a column from bottom to top) satisfy this regularity requirement and more typically all scans in which rows and columns are scanned from right to left or from left to right. G. Borgefors advocates a double scan of pixels in the image, once in the lexicographic order and another in the inverse lexicographic order.

The figure 8a shows, in the case of a scan pass in the lexicographic order from the upper left corner to the lower right corner of the image, the boxes of the chamfer mask of the figure 1 used to list the paths from a goal pixel placed under the central box (box indexed by 0) to the source pixel through a neighborhood pixel whose distance has already been estimated during the same scan . These boxes are eight in number, arranged in the upper left part of the chamfer mask. There are thus eight paths listed for the shortest search whose length is taken for estimation of the distance.

The figure 8b shows, in the case of a scanning pass in the inverse lexicographic order from the lower right corner to the upper left corner of the image, the boxes of the chamfer mask of the figure 1 used to list the paths from a goal pixel placed under the central box (box indexed by 0) to the source pixel through a neighborhood pixel whose distance has already been estimated during the same scan . These boxes are complementary to those of the figure 8a . They are also eight in number but arranged in the lower right part of the chamfer mask. There are thus still eight paths listed for the search of the shortest whose length is taken for estimation of the distance.

The propagation distance transform of which the principle has just been summarily recalled was originally conceived for the analysis of the positioning of objects in an image but it was not slow to be applied to the estimation of the distances on a relief map extracted from a database of elevation of the land with regular mesh of the terrestrial surface. Indeed, such a map does not explicitly have a metric since it is drawn from the altitudes of the points of the mesh of the elevation database of the terrain of the zone represented. In this context, the propagation distance transform is applied to an image whose pixels are the elements of the terrain elevation database belonging to the map, that is to say, associated altitude values. to the geographical coordinates latitude, longitude of the nodes of the mesh where they were measured, classified, as on the map, by latitude and by longitude increasing or decreasing according to a two-dimensional array of latitude and longitude coordinates.

In the case of an aircraft, the evolution of the impassable zones according to the vertical profile imposed on the trajectory of the aircraft is taken into account by means of the foreseeable altitude of the aircraft at each goal point whose distance is currently being estimated. This predictable altitude, which obviously depends on the path taken, is that of the aircraft after tracking the path adopted for the distance measurement. The estimate of this foreseeable altitude of the aircraft at a goal point is done by propagation during the scanning of the image by the chamfer mask in a manner similar to the distance estimation. For each path listed from a point of focus to a point of source passing through a point in the vicinity of the point of view whose distance to the source point and the expected altitude of the aircraft have already been estimated during the same sweep, the Predictable altitude of the aircraft is deduced from the length of the path and the vertical profile imposed on the trajectory of the aircraft. This predicted altitude, estimated for each listed route from an aiming point whose distance is being estimated to a source point placed near the position of the aircraft, is used as a selection criterion for the trips taken in account in the distance estimation. If it corresponds, taking into account a safety margin, to a basic airspace representation cube whose level of danger is greater than the threshold required for the flight, that is to say, a portion of altitude prohibited because in the relief or in a weather disturbance, the listed route with which it is associated is discarded and does not participate in the selection of the shortest route. Once the selection of the shortest route has been made, its length is taken for distance from the aiming point and the expected altitude for the aircraft associated with it is also selected for the altitude of the aircraft at the point of aim.

We have: on the one hand, a profile presenting the altitude as a function of the distance from the origin. It is used to estimate the altitude that the aircraft can have based on the distance propagated that is evaluated on the grid. On the other hand, we have a profile showing the date according to the distance from the origin. This profile is obtained, for example, by integrating the speed provided by the flight management system along the flight plan or by making assumptions of speed (constant, for example). So, from the estimated distance, we can deduce the date at which we should be at this distance.

• ■ lire la distance estimée D_V du point voisin P_V (étape 90),
• ■ lire le coefficient C_XY du masque de chanfrein correspondant à la case occupée par le point voisin P_V(étape 91),
• ■ calculer la distance propagée D_P correspondant à la somme de la distance estimée D_V du point voisin P_V et du coefficient C_XY affecté à la case du masque de chanfrein occupée par le point voisin P_V: $$\begin{array}{cc}{D}_P=D_V+{\mathrm{<figure-callout\; id="92"\; label="C\; XY\; étape"\; filenames="imgf0007.png"\; state="\{\{state\}\}">C</figure-callout>}}_{\mathit{XY}}& \left(\mathrm{étape}\right)\left(92\right)\end{array},$$
  
• ■ calculer l'altitude prévisible A_P de l'aéronef après franchissement de la distance D_P directement à partir de la distance D_P si le profil vertical imposé à la trajectoire de l'aéronef est défini en fonction de la distance parcourue PV(D_P) et prend implicitement en compte le temps de parcours ou indirectement par l'intermédiaire du temps de parcours si le profil vertical imposé à la trajectoire de l'aéronef est défini par une vitesse de changement d'altitude (étape 93),
• ■ calculer la date prévisible Tp à la position après franchissement de la distance D_P (étape 94)
• ■ lire le niveau de danger N_i,j,Ap,Tp prévisible du point but P_i,j dans la représentation en cubes élémentaires de l'espace aérien à l'altitude prévisible A_P et à date Tp (étape 95),
• ■ comparer le niveau de danger prévisible N_i,j,Ap,Tp à une valeur limite autorisée N_l pour le vol, augmentée d'une marge de sécurité Δ (étape 96),
• ■ éliminer la distance propagée D_P si le niveau de danger prévisible N_i,j,Ap,Tp est supérieur à celui admissible pour le vol majoré par la marge de sécurité Δ (étape 97),
• ■ si le niveau de danger prévisible N_i,j,Ap,Tp majoré par la marge de sécurité Δ, est inférieur à la limite N_l fixée pour le vol, lire la distance D_i,j déjà affectée au point but considéré P_i,j ( étape 98) et la comparer à la distance propagée D_P (étape 99),
• ■ éliminer la distance propagée D_P si elle est supérieure ou égale à la distance D_i,j déjà affectée au point but considéré P_¡,j, et
• ■ remplacer la distance D_i,j déjà affectée au point but considéré P_i,j, par la distance propagée D_P si cette dernière est inférieure (étape 900).
• ■ les cubes élémentaires présentant une distance inférieure à la plus grande distance mesurable sur l'image à la fin du balayage, étant désignés zone atteignables.

The figure 9 illustrates the main steps of the processing carried out during the application of the chamfer mask to a goal point P _{i, j} to estimate its distance for an aircraft having a prescribed vertical profile of trajectory. The goal point considered P _{i, j} is placed in the central box of the chamfer mask. For each neighbor point P _V that enters the chamfer mask boxes and whose distance has already been estimated during the same scan, the treatment consists of:

• ■ read the estimated distance D _V from the neighbor point P _V (step 90),
• ■ read the coefficient C _XY of the chamfer mask corresponding to the square occupied by the neighboring point P _V (step 91),
• ■ calculate the propagated distance D _P corresponding to the sum of the estimated distance D _V of the neighbor point P _V and of the coefficient C _XY assigned to the chamfer mask box occupied by the neighbor point P _V : $$\begin{array}{cc}{D}_P=D_V+{\mathrm{<figure-callout\; id="92"\; label="VS\; XY\; step"\; filenames="imgf0007.png"\; state="\{\{state\}\}">VS\; </figure-callout>}}_{\mathit{XY}}& \left(\mathrm{step}\right)\left(92\right)\end{array},$$
  
• Calculating the predicted altitude A _P of the aircraft after crossing the distance D _P directly from the distance D _P if the vertical profile imposed on the trajectory of the aircraft is defined according to the distance traveled PV (D _P ) and implicitly takes into account the travel time or indirectly via the travel time if the vertical profile imposed on the trajectory of the aircraft is defined by a speed of change of altitude (step 93),
• Calculating the expected date Tp at the position after crossing the distance D _P (step 94)
• ■ read the level of danger N _{i, j, Ap, Tp} predictable goal point P _{i, j} in the representation in cubic airspace at the expected altitude A _P and date Tp (step 95),
• Comparing the foreseeable level of danger N _{i, j, Ap, Tp} to an authorized limit value N _l for the flight, increased by a safety margin Δ (step 96),
• ■ eliminating the propagated distance D _P if the foreseeable danger level N _{i, j, Ap, Tp} is greater than that allowed for the flight plus the safety margin Δ (step 97),
• ■ if the foreseeable level of danger N _{i, j, Ap, Tp} plus the safety margin Δ, is lower than the limit N _l fixed for the flight, read the distance D _{i, j} already affected at the point of interest considered P _{i , j} (step 98) and compare it to the propagated distance D _P (step 99),
• ■ eliminate the propagated distance D _P if it is greater than or equal to the distance D _{i, j} already assigned to the considered goal point P _{¡, j} , and
• ■ replace the distance D _{i, j} already assigned to the goal point P _{i, j} , by the propagated distance D _P if the latter is lower (step 900).
• ■ the elementary cubes having a distance smaller than the greatest distance measurable on the image at the end of the scan, being designated zone reachable.

The complete scanning of the image is similar to that described in the aforementioned patent application.

A rejoining point selected is a point in the initial flight plan remaining attainable despite the multiple constraints of the aircraft and surrounding weather events. In addition, there must be a flight plan to reach this point, compatible with the available fuel resources.

Among the points of rejoin retained, one chooses a point optimizing a criterion of quality. To illustrate these quality criteria, we take the example of an initial trajectory represented figure 10 and a joining path. The initial trajectory is formed by the points A, B, C, D, E and F. The rejoining trajectory is formed by the points B ', C', D 'and E.

A first quality criterion is the maximization of the number of crossing points of the initial flight plan retained. The rejoining path of the example retains three points of the initial trajectory: A, E and F.

A second quality criterion is the minimization of the amount of total turn equal to the sum in absolute value of all course changes.

A third quality criterion concerns a measure of the ratio between the initial trajectory and the new trajectory evaluated. A rejoin flight plan is even better than its length is close to that of the initial flight plan.

A fourth quality criterion is the minimization of the joining angle of the initial flight plan. This is the angle formed by the rejoining trajectory and the initial trajectory at the rejoining point. In the example, this is the angle α between the flight segment D'E and the segment EF.

A fifth quality criterion is the minimization of the deviation surface from the initial flight plan. The deviation surface is defined by its perimeter composed of the initial trajectory and the rejoining trajectory. In the example, it is the polygon surface B, C, D, E, D ', C', B '.

où Ci est le score du critère i (i=1 à 5) et α_i est la « puissance » attribuée - par configuration - au critère i. En affectant une puissance plus élevée, on augmente l'influence du critère.One can also choose a point optimizing a weighted combination of several of the preceding criteria. The combination of criteria can be performed according to the following formula: $$\mathrm{VS}=\left[{\left({\displaystyle \underset{i=1}{\overset{\mathrm{not}}{\Pi }}}{\left(1+{\mathrm{VS}}_i\right)}^{{\alpha }_i}\right)}^{\frac{1}{{\displaystyle \underset{i)1}{\overset{\mathrm{not}}{\Sigma }}}{\alpha }_i}}-1\right]$$

where Ci is the score of criterion i (i = 1 to 5) and α _i is the "power" attributed - by configuration - to criterion i. By assigning a higher power, the influence of the criterion is increased.

Depending on the application for which the invention is intended, the powers can be adjusted differently. For example, a military application will try to limit the number of points removed and the area between the two paths. For example, an application for a medical helicopter will try to limit the difference in distance between the trajectories, even if the crossing points are different.

Each of the criteria presented above must be standardized to be able to be in the previous formula. The Figures 11a to 11e show examples of curves to standardize the different quality criteria presented. These curves make it possible to associate with each value of a criterion a score, between 0 and 1, reflecting its quality, 0 being the worst and 1 the best.

The figure 11 a shows an example of the ratings assigned to a joined flight plan based on the number of waypoints retained in relation to an initial flight plan. Between 0 and 3 points preserved the note is null, for 4 points preserved the note is 0,5. Beyond 5 points, the score is 1.

The figure 11 b shows an example of the ratings assigned to a joined flight plan based on its total turn quantity. The rating is 1 to 0 degrees. Between 0 and 360 degrees the note decreases linearly. The rating is 0 beyond 720 degrees. Between 360 and 720 degrees, the note decreases linearly.

The figure 11 c shows an example of the ratings assigned to a joined flight plan based on the ratio of the length of the initial trajectory to its length. Between 0 and 0.8 the rating is zero. Between 0.8 and 1 the note grows linearly. For 1 the rating is 1. Above 1.5 the rating is zero. Between 1 and 1.5 the score decreases linearly.

The figure 11d shows an example of the ratings assigned to a joined flight plan based on the flight plan rejection angle. Between 0 and 30 degrees the rating is 1. Above 120 degrees the score is 0. Between 30 and 120 degrees the score decreases linearly.

The figure 11 e shows an example of the ratings assigned to a joined flight plan based on the deviation area from the initial flight plan. Among all the candidates, we take the smallest as a reference. The others are expressed as a percentage of this reference area. At 100% the rating is 1. Above 200% the rating is 0. Between 100% and 200% the rating decreases linearly.

Among the five criteria mentioned above, there are two criteria dependent solely on the point of rejoin, and therefore independent of a reference trajectory, and three criteria dependent on a comparison between the initial trajectory and the rejoining trajectory.

To calculate a weighted combination of several of the preceding criteria, it is possible to first evaluate the criteria that do not require a reference trajectory. Then, we keep a number of points (for example three) the highest ranked according to the formula already described applied to the evaluated criteria. Then for each of the points retained, one can calculate the corresponding rejoining trajectory. For each of the calculated rejection paths, the criteria using the initial trajectory and the evaluated trajectory are evaluated. In the end, we keep the best-matched joining point according to the combination of the five criteria.

The device according to the invention comprises means for the calculation of a rejection flight plan towards the selected rejoin point 106. This calculation step is based on a method described in the French patent. 2,894,367 developing the "return" distance map from the selected destination position.

• l'élaboration de deux cartes de distances couvrant une zone d'évolution contenant les points de départ et de destination et renfermant le même ensemble d'obstacles à contourner prenant en compte le relief, les zones à survol réglementé et les profils verticaux de vol et de vitesse imposés au départ et/ou à l'arrivée, la première ayant le point de départ pour origine des mesures de distance et la deuxième, le point de destination pour origine des mesures de distance,
• l'élaboration d'une troisième carte de distances par sommation, pour chacun de ses points, des distances qui leur sont affectées dans les première et deuxième cartes de distances,
• le repérage dans la troisième carte de distances, d'un ensemble connexe de points iso-distances formant un enchaînement de parallélogrammes et/ou de points reliant les points de départ et de destination,
• la sélection, dans l'ensemble connexe repéré de points iso-distances, d'une suite de points consécutifs allant du point de départ au point de destination en passant par des diagonales de ses parallélogrammes, suite dite trajet direct,
• l'approximation de la suite de points du trajet direct par une chaîne de segments droits respectant un seuil arbitraire d'écartement maximum par rapport aux points de la suite et un seuil arbitraire d'écartement latéral minimum par rapport à l'ensemble d'obstacles à contourner, et
• le choix des points des jonctions intermédiaires des segments droits en tant que points de passage ou tournants du plan de vol.

The determination of a flight plan leading from the current position of the aircraft to the selected rejoining point while respecting flight constraints comprises the following steps:

• the development of two distance maps covering an area of evolution containing the points of departure and destination and containing the same set of obstacles to be circumvented taking into account terrain, areas with prescribed overflight and vertical flight profiles and imposed on departure and / or arrival, the first having the starting point for the origin of the distance measurements and the second, the destination point for the origin of the distance measurements,
• developing a third distance map by summing, for each of its points, the distances assigned to them in the first and second distance maps,
• locating in the third distance map a connected set of iso-distance points forming a sequence of parallelograms and / or points connecting the departure and destination points,
• selecting, in the related connected set of iso-distance points, a sequence of consecutive points from the point of departure to the point of destination via the diagonals of its parallelograms, following said direct path,
• the approximation of the sequence of points of the direct path by a chain of straight segments respecting an arbitrary maximum separation threshold with respect to the points of the sequence and an arbitrary threshold of minimum lateral spacing with respect to the set of obstacles to bypass, and
• the choice of the points of the intermediate junctions of the straight segments as points of passage or turning points of the flight plan.

The calculation of a joined flight plan described above can be repeated at regular intervals. The current flight plan of the aircraft is not updated for every iteration of the calculation. The current flight plan is kept as long as, on the one hand, it remains valid and, on the other hand, as long as the gain on the quality criterion of the new flight plan calculated in relation to the current flight plan is less than one given threshold.

Claims (10)

Device for calculating a flight plan of an aircraft, said flight plan allowing rejection to an initial flight plan, said aircraft comprising sensors for the detection of surrounding mobiles and weather sensors for the detection of meteorological phenomena , said device being characterized in that it comprises means for: The determination of parameters characterizing the detected mobiles (101) from data coming from the sensors for the detection of surrounding aircraft, Determining parameters characterizing the detected weather phenomena, (102) from meteorological data from the weather sensors, ■ the calculation of forbidden zones and their evolution over time (103) from the parameters characterizing the aircraft and the detected meteorological phenomena, said zones defining a space where the aircraft can not fly, The calculation of areas attainable by the aircraft and their evolution over time (104) from the position of the aircraft, data describing prohibited restricted areas to navigation, a digital terrain model, a list of obstacles and calculated prohibited areas, ■ selecting a joining point of the initial flight plan (105) located in an attainable area, ■ calculating a joining flight plan to the selected joining point (106). Device according to claim 1, characterized in that the calculation of the rejoin flight plan is iterated at regular intervals, a flight plan being evaluated according to a quality criterion and in that a calculated flight plan at a given iteration, referred to as a new flight plan, becomes the flight plan followed by the aircraft if a joined flight plan, calculated at a previous iteration and followed by the aircraft, called the current flight plan, presents an evaluation , in the sense of the quality criterion, the difference of which with the evaluation of the new calculated flight plan is greater than a given threshold. Device according to one of the preceding claims, characterized in that the calculation of reachable areas comprises an estimation of the distances of the points in a map obtained by projection on a horizontal plane of a 3D representation of a space of evolution by a mesh of elementary cubes associated with danger levels and marked by an altitude, a latitude, a longitude and a date, said estimation consisting in applying a distance transform, the cubes associated with danger levels higher than a permissible value N _l spotting prohibited areas for the aircraft; said distance transform estimating the distances of the different points of the image with respect to a source point representing the position of the aircraft by applying, by scanning, a mask at the different points of the image; a determined initial distance value being assigned, at the start of scanning, to all the points of the image except at the source point, the origin of the distance measurements, which is assigned a value of zero distance. Device according to claim 3, characterized in that the distance estimation of the source point to a point considered P _{i, j} , said goal point, being placed in a particular cell of the mask, consists for each neighboring point P _V entering the boxes of the mask and whose distance has already been estimated during the same scan to: ■ read the estimated distance D _V from the neighbor point P _V (step 90), ■ read a coefficient C _XY of the mask corresponding to the square occupied by the neighboring point P _V (step 91), ■ calculate a propagated distance D _P corresponding to the sum of the estimated distance D _V of the neighbor point P _V and the coefficient C _XY assigned to the mask space occupied by the neighboring point P _V : $$\begin{array}{cc}{D}_P=D_V+{\mathrm{VS}}_{\mathit{XY}}& \left(\mathrm{step}92\right)\end{array},$$

■ calculate a predictable altitude A _P of the aircraft after crossing the distance D _P (step 93), Compute a propagated date Tp at the position after crossing the distance D _P (step 94) ■ read a predictable level of danger N _{i, j, Ap, Tp} of the goal point P _{i, j} in the representation in elementary cubes of the airspace at the predictable altitude A _P and propagated date Tp (step 95), Comparing the foreseeable level of danger N _{i, j, Ap, Tp} to an authorized limit value N _l for the flight, increased by a safety margin Δ (step 96), ■ eliminating the propagated distance D _P if the foreseeable danger level N _{i, j, Ap, Tp} is greater than that allowed for the flight plus the safety margin Δ (step 97), ■ if the foreseeable level of danger N _{i, j, Ap, Tp} plus the safety margin Δ, is lower than the limit N _l fixed for the flight, read the distance D _{i, j} already affected at the point of interest considered P _{i , j} (step 98) and compare it to the propagated distance D _P (step 99), ■ eliminate the propagated distance D _P if it is greater than or equal to the distance D _{i, j} already assigned to the considered goal point P _{i, j} , and ■ replace the distance D _{i, j} already assigned to the goal point P _{i, j} , by the propagated distance D _P if the latter is lower (step 900). ■ the elementary cubes having a distance smaller than the greatest distance measurable on the image at the end of the scan, being designated zone reachable. Device according to one of the preceding claims, characterized in that the selection of the joining point comprises the calculation of a note C for points of the initial flight plan situated in an attainable zone, the point of rejoining the initial flight plan. selected being the one obtaining the best score C, said score being calculated according to the following relation: $$\mathrm{VS}=\left[{\left({\displaystyle \underset{i=1}{\overset{\mathrm{not}}{\Pi }}}{\left(1+{\mathrm{VS}}_i\right)}^{{\alpha }_i}\right)}^{\frac{1}{{\displaystyle \underset{i)1}{\overset{\mathrm{not}}{\Sigma }}}{\alpha }_i}}-1\right]$$

where Ci is a score given according to an evaluation criterion i, and α _i is a value associated with the evaluation criterion i and reflecting its importance, being a value between 1 and 5. Device according to one of the preceding claims, characterized in that the parameters characterizing the detected mobiles comprise a speed, a position and a future flight plan. Device according to claim 6, characterized in that the prohibited zone associated with a mobile characterized solely by its position is defined by a succession of concentric circles with radii (402), (403) obeying an increasing law as a function of time and whose center is the position (401) of said mobile. Device according to one of claims 6 or 7, characterized in that the prohibited zone associated with a mobile characterized by its position and by its speed vector is defined by a succession of cylinders, whose centers correspond to the predicted position of said mobile to from said velocity vector, said centers being spaced apart by a regular interval of time p, the radii of the successive cylinders obeying an increasing law as a function of time and respecting the following relation: $${\mathrm{r}}_{\mathrm{i}}\mathrm{+}{\mathrm{r}}_{\mathrm{i}\mathrm{+}\mathrm{1}}\mathrm{>}\mathrm{p}$$

where p is the time interval separating the centers of two successive cylinders, r _i and r _{i + 1} represent the radii of two successive cylinders. Device according to one of claims 6 to 8, characterized in that the prohibited area associated with a mobile characterized by its position and by its future flight plan is defined by a tube enveloping the flight plan. Device according to one of claims 6 to 8, characterized in that the prohibited area associated with a mobile characterized by its position and by its future flight plan is defined by a rectangular parallelepiped enveloping the flight plan.

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