Device and method for calculating a safe 4D aircraft trajectory

Abstract

The present invention provides a device and method for calculating a safe 4D aircraft trajectory for avoiding conflicts with fixed or moving objects. The device of the invention comprises a trajectory safety module interacting with a flight management system, which consists of a functional module for conflict risk assessment and a functional module for conflict resolution. The conflict resolution results in a hierarchical list of solution trajectories, which can be based on lateral and / or vertical resolution and / or a combination thereof, depending on the aircraft's current state, the nature of the conflict, and the type of object. Figure 1 (for the abstract)

Description

Title of the invention: Device and method for calculating a secure 4D trajectory for an aircraft Technical field

[0001] The present invention relates to the field of flight management and more specifically relates to a method for calculating a 4D trajectory for an aircraft and securing it against fixed or mobile elements which could come into conflict on the trajectory. State of the art

[0002] Flight management systems or flight managers, known generically as "Flight Management System" (FMS), provide pilots with assistance during flight by providing information on piloting, navigation, estimates, fuel consumption, etc.

[0003] There are different flight management systems whose capabilities and functionalities can vary greatly depending on the aircraft (helicopter, airliner, etc.), its use (civil, military, etc.) and other factors (design period in particular).

[0004] The following functionalities or services are commonly available on an FMS: a navigation database; a flight plan; a trajectory; guidance; location. The pilot has human-machine interfaces (HMI) allowing him to manage a flight plan, before departure, during navigation.

[0005] The navigation database or "Navigation Database" (NDB) according to the known Anglicism, contains all the information necessary for the development and monitoring of the flight plan, including in particular: air routes ("Airways" according to the known Anglicism); route points or waypoints ("Waypoints" according to the known Anglicism); airports and their different runways; approach procedures ("Standard Arrivai" or (STAR) according to the known Anglicism), and departure procedures ("Standard Instrument Departure" or (SID) according to the known Anglicism); other information concerning ground installations.

[0006] A flight plan is made up of a series of waypoints ('waypoints' according to the known Anglicism) whose structure is defined by standard norms. These points are connected by segments (a segment or 'leg' being defined as a unitary portion of the flight plan reaching a final condition according to a maneuver specified by the type of the leg, the types of legs according to the ARINC 424 standard defining the different means of flying between two waypoints).

[0007] From a flight plan, the FMS can calculate a reference trajectory to follow, which is displayed on display screens, with an estimate of a set of data that may be useful to the pilot during the flight, such as the times of passage at the various waypoints in the flight plan, the estimate of the quantity of fuel on board, etc.

[0008] The results of the calculations performed by an FMS computer as well as the flight information are generally rendered on display systems coupled to the FMS to transform the data into readable information.

[0009] A trajectory calculated by an FMS is called a 4D trajectory insofar as it considers all the positions of the aircraft in the three spatial dimensions with a time reference for each position. A 4D trajectory is a sequence of points describing the vertical, lateral and longitudinal profiles of the flight of an aircraft. Each point is described by three position coordinates (e.g. latitude, longitude and altitude) and a time coordinate.

[0010] Some FMS include a guidance system. Once a trajectory has been calculated, the pilot can choose to follow it manually or automatically (the FMS is then coupled to an autopilot which is responsible for piloting the aircraft according to the guidance orders sent by the FMS). In both cases, the guidance system provides the information necessary to follow this trajectory (speeds, angles, altitude, speed to be reached, etc.), and can even take charge of some of the actions to be carried out.

[0011] In flight, one of the main tasks of a flight management system is the precise determination of the location of the aircraft. To do this, the system generally has several sources of navigation data, positioning systems and sensors, such as VOR, GPS, DME, 1RS for example.

[0012] The FMS is therefore a main element of the avionics of a modern aircraft, its task being to reduce the workload of the crew in flight planning, performance management, piloting the aircraft, measuring flight parameters, navigation. Thus, the FMS is able to control the entirety of a flight, from takeoff to landing by carrying out all the necessary calculations, through a flight management computer or "Flight Management Computer" (FMC) according to the known Anglicism.

[0013] As long as the aircraft follows a published procedure, it is guaranteed to be protected. However, for various reasons (air traffic control, weather), the aircraft may find itself off the theoretical trajectory, with a need to catch up with it in the more or less long term. These non-nominal situations are very frequent, and avionics products are not very well adapted to them. In particular, no indication exists to help a crew gauge its situation with regard to a potential terrain / weather conflict on a rejoin trajectory towards the initial flight plan. In cases where these trajectory deviations are managed manually by the pilot with heading control, no rejoin trajectory is calculated. and the joining portion is even less verified in relation to a possible land conflict.

[0014] Thus, when a trajectory calculated by an FMS passes through areas considered to be unsafe, for example located outside a published procedure, the FMS does not have the native capacity to propose a trajectory which could avoid any type of conflict, for example a terrain or weather conflict, a physical obstacle, an area closed to navigation or any other fixed or mobile physical object or any modelable logic having operational relevance.

[0015] This technical problem can appear when air traffic control asks the pilot to deviate from his reference trajectory, for example in the terminal phase. In this operational case, most known FMS do not implement a function for calculating the trajectory for rejoining the initial flight plan, leaving the pilots and air traffic control responsible for navigation, with very limited information in the cockpit.

[0016] Each stakeholder creates their own mental representation of a rejoining of the initially planned route (the reference trajectory), without this being materialized on a map or in a system, or even verbalized. In fact, this situation considerably increases the mental load of the pilots.

[0017] There are proposals for calculating a flight plan rejoin trajectory. The Applicant's patent applications FR3031175 B1, FR3051057 B1, FR3064351 B1 are examples of flight plan rejoin trajectory calculation, respectively for a lateral rejoin, a vertical rejoin, a delayed rejoin. In these solutions, the flight plan rejoin trajectory is always calculated according to a simplified hypothesis from the current position of the aircraft, which may make it possibly unflyable for an immediate return to the flight plan (because it is unsafe or causes a conflict due to an obstacle or a possible energy management problem), or which may sometimes lead to a rejoin to an active segment which is no longer operationally relevant.

[0018] Thus, various flight plan joining strategies are possible, favoring or not an intersection of the flight plan with the current heading instruction of the aircraft. When no intersection exists between the current heading instruction and the flight plan, the joining trajectory captures, from the current position and the current heading of the aircraft, one of the “legs” of the flight plan at a determined angle (often 45° or 90° depending on the situation of the aircraft).

[0019] However, currently there is no guarantee in the construction of a permanent joining trajectory that it will not come into conflict with terrain or weather obstacles.

[0020] Also, assistance from a computer of a flight management system of a aircraft would be desirable. However, such assistance must be able to ensure that the joining trajectory which is automatically constructed does not cross any fixed or moving obstacle (terrain, weather, air traffic or prohibited airspace), i.e. that it is secure.

[0021] However, there is currently no solution allowing the construction by a flight management system computer of a 4D trajectory for joining a flight plan, which is secure with respect to all types of conflicts: terrain, obstacles, weather, aircraft, or airspace.

[0022] Managing trajectory security increases the workload of pilots, who must cross-reference the various information available to them: the view from outside the cockpit; instructions from air traffic control (e.g. heading, altitude, speed, etc.); information from weather radar (if the aircraft is equipped with it); information from other traffic; information from published procedures, which are by definition protected from obstacles and terrain but likely to be occupied by aircraft; information from warning systems.

[0023] Furthermore, in a context of reduction in the number of pilots in the aircraft, with the emergence of the concepts of "Single Pilot Operations" (SPO), or the solutions without a pilot on board "Remotely Piloted Aircraft System" (RPAS), it is necessary to reduce as much as possible the load of the flight operator (pilot, remote pilot), as well as that of the air traffic controller, in particular in complex flight phases such as the approach. It is also appropriate to cover cases of incapacitation of the only pilot on board, an event whose occurrence does not allow it to be excluded from safety analyses.

[0024] Various systems have been developed to warn a crew of a risk of collision with the ground and thus help them manage navigation safety. Some, such as TAWS (Terrain Awareness and Warning System) systems, make a short-term trajectory forecast for the aircraft based on current flight information (position, heading, orientation and amplitude of the speed vector), provided by the on-board equipment, and place it in situation in relation to a map of the region flown over (extracted from a terrain elevation database accessible from the on-board). They can issue alarms to the aircraft crew each time the short-term predictable trajectory collides with the terrain. These are aid and alert solutions that work on a short-term timescale, of the order of 3 minutes in front of the aircraft.They are intended to provide a so-called tactical "reaction" solution, and in general the maneuver must be carried out by the crew.

[0025] Existing terrain avoidance systems, for example, rely on the terrain near the aircraft to issue alerts. However, no navigation system can anticipate a terrain conflict that would occur further downstream on the aircraft's trajectory when it finds itself outside the procedure corridor.

[0026] Other systems such as integrated weather radar systems provide the crew with weather information around the aircraft (precipitation, wet hail, wet turbulence and wind shear). Based on the information collected, the air traffic control personnel and the pilot work together to manually select a new route after analysis.

[0027] These systems provide indications and aids. However, there is no system building a strategic trajectory, i.e. with a longer deadline (at least 10 minutes in front of the aircraft) which is secure.

[0028] Thus, there is a need to provide pilots with a solution enabling the automatic construction of a secure 4D trajectory for an aircraft, i.e. a 4D trajectory which is free of conflict.

[0029] The present invention meets the need. Summary of the invention

[0030] An object of the invention is thus to overcome the shortcomings of the prior art by proposing a process resulting in the automatic construction of an alternative 4D trajectory, secure against any type of conflict.

[0031] Advantageously, the trajectory securing method of the present invention makes it possible to reduce the workload of the pilots.

[0032] In one embodiment, the crew can choose to automatically control the aircraft on the alternative trajectory, and initiate its tracking, for example in the event of an imminent conflict.

[0033] An object of the present invention is a method (and an associated device) for calculating a continuous 4D trajectory, which in its construction has compiled the various conflict information in order to propose a trajectory free of any conflict (meteorological, terrain, traffic, unauthorized zone, etc.).

[0034] Advantageously, the present invention applied to the aeronautical field makes it possible to increase the safety of a flight, to facilitate decision-making and negotiations and discussions with air traffic control (ATC) (from the English "Air Traffic Control").

[0035] In a (SPO) context ("Single Pilot Operations" according to the accepted Anglicism), the present invention significantly reduces the pilot's workload and allows the system, in the event of the pilot's incapacity, to land the aircraft autonomously and safely.

[0036] Another object of the invention is to propose a solution to alert on a future conflict if nothing is done in the short term, or even to develop automatisms to reduce the workload of a crew or a drone operator, but also to propose a solution to deal, in a single-pilot world, with a possible incapacity of the latter.

[0037] The device of the invention can advantageously be coupled to a ground / on-board data exchange system to enable the controller to take into account the proposal of the on-board system in the instructions sent to the aircraft.

[0038] The device of the invention can also be coupled to trajectory safety systems such as TAWS (Terrain Avoidance Warning System), TCAS (Traffic Collision Avoidance System) or other devices making it possible to warn a crew of a possible conflict with an obstacle (meteorological, terrain, traffic, closed air sector, etc.).

[0039] Advantageously, the trajectory securing method according to the invention proves to be particularly effective for different operational cases such as the determination of contingency or emergency trajectories to diversion airports, in particular in single-pilot cockpit contexts.

[0040] The invention can be preferably used in connection with a flight management system of the FMS type. It can be easily customized to different versions of flight management systems (including systems for unmanned vehicles).

[0041] The invention can be generalized for use in connection with any trajectory management system for land or sea vehicles. Thus, the present invention is applicable to all piloted aircraft, in flight or on the ground, and equipped with a trajectory management system.

[0042] The invention will find advantageous applications in a “dual-pilot” or “single-pilot” or drone world, to secure the reference trajectory of an aircraft, in order to allow, for example: - loading a conflict-free trajectory into an on-board trajectory calculator such as FMS; - display in an EFB (“Electronic Flight Bag”) via trajectory security applications; - implementation in ground tools usable by air traffic control; - implementation in ground tools usable by an airline control center with the possibility of exporting to an on-board flight management system.

[0043] To obtain the desired results, a method for calculating a secure 4D trajectory for an aircraft is proposed. The method comprises the following steps: - determine, by a computer external to the aircraft flight management system, whether on a current 4D trajectory calculated by the flight management system, there is a risk of conflict for the aircraft with at least one object; - if there is no risk of conflict, define the current 4D trajectory as a safe trajectory for the aircraft; or - if there is a risk of conflict: - calculating, by the computer external to the flight management system, a hierarchical set of solution trajectories with their conflict avoidance parameters, allowing the aircraft to avoid a conflict with said at least one object, said conflict avoidance parameters being obtained and hierarchical by the implementation of a conflict resolution procedure; - calculate, by the aircraft flight management system, a modified 4D trajectory from the conflict avoidance parameters provided by the computer external to the flight management system; and - determine by the computer external to the flight management system, whether on the modified 4D trajectory, there is a new risk of conflict for the aircraft with at least one other object; - if there is no risk of conflict, define the modified 4D trajectory as a safe trajectory for the aircraft; or - if there is a risk of conflict, repeat the previous steps until a conflict resolution is reached.

[0044] The invention proposes several embodiments.

[0045] According to a particular aspect of the invention, the step of determining the risk of conflict by the computer external to the flight management system, comprises steps consisting of identifying from different data sources, at least the presence of fixed or moving obstacles on the current or modified 4D trajectory, and of verifying whether the obstacle(s) can generate a conflict with the aircraft.

[0046] According to a particular aspect of the invention, the step of determining the risk of conflict by the computer external to the flight management system further comprises a step consisting of generating a list of conflicts identifying for each type of conflict conflict avoidance parameters.

[0047] According to a particular aspect of the invention, the conflict avoidance parameters are safety altitudes and / or heading values ​​and / or speed values.

[0048] According to a particular aspect of the invention, the step of determining the risk of conflict by the computer external to the flight management system further comprises steps consisting of determining the current flight phase of the aircraft and determining the corresponding conflict resolution procedure.

[0049] According to a particular aspect of the invention, the step of implementing a conflict resolution procedure consists of implementing one or more conflict resolution algorithms among vertical resolution, lateral resolution or mixed resolution algorithms.

[0050] According to a particular aspect of the invention, the step of implementing a conflict resolution procedure consists of implementing a sequence of several conflict resolution algorithms, the sequence being predefined or configurable.

[0051] According to a particular aspect of the invention, the step of implementing a conflict resolution procedure consists of taking into account one or more intermediate trajectories calculated during the iteration phase.

[0052] The invention also relates to a device for calculating a secure 4D trajectory for an aircraft, the device comprising means configured to implement the steps of the method for securing a 4D trajectory for an aircraft of the invention.

[0053] Another object of the invention is a flight management system comprising means for operating with a device for calculating a secure 4D trajectory for an aircraft according to the invention.

[0054] An object of the invention also addresses an aircraft comprising a flight management system and a device for calculating a secure 4D trajectory for an aircraft according to the invention.

[0055] The invention also relates to a computer program comprising code instructions making it possible to carry out the steps of the method for calculating a secure 4D trajectory for an aircraft of the invention, when said program is executed on a computer. Brief description of the drawings

[0056] Other features and advantages of the present invention will become more apparent upon reading the following description in relation to the following drawings.

[0057] [Fig.l] represents a block diagram of the device of the invention in interaction with a flight management system of an aircraft;

[0058] [Fig.2] represents a general synopsis of the different stages of the 4D trajectory securing method of the invention, in one embodiment;

[0059] [Fig.3] represents a block diagram of the stages of staged conflict resolution, in one embodiment of the invention;

[0060] [Fig.4] represents a block diagram of a 4D trajectory securing method according to the invention, during a descent phase of an aircraft;

[0061] [Fig.5] represents a display of a pseudo-waypoint on a navigation screen of an aircraft, in one embodiment of the invention;

[0062] [Fig.6] illustrates for a selected descent mode, the display on a navigation screen of an aircraft, of a conflict zone and of a detected conflict point, according to an embodiment of the invention;

[0063] [Fig.7] represents a block diagram of lateral conflict resolution steps in one embodiment of the invention;

[0064] Figures 8a and 8b illustrate an implementation of a multi-dimensional conflict resolution according to the invention using a “graph traversal” type approach. Detailed description of the invention

[0065] [Fig. 1] represents a block diagram of the device 100 of the invention in interaction with a flight management system of an aircraft. The flight management system 102, the main function of which is to ensure the management of a determined flight plan, is illustrated by way of simplified example as an FMS where only the main components for flight plan management, trajectory calculation, prediction calculation and guidance are shown. From the information from the flight plan and a certain amount of information from the sensors of the aircraft (location means, automatic pilot), the management of the flight plan consists of continuously calculating the trajectory of the aircraft and developing a certain number of predictions. A prediction is understood to mean the value of a piloting or navigation parameter concerning the present or future of the flight.For example, a prediction about the future of the flight is the remaining flight time until the aircraft lands or the maximum flight distance taking into account the fuel reserves. The trajectory calculation and the predictions allow the aircraft to be guided, with the guidance information being taken into account in the management of the flight plan.

[0066] The guidance function provides in particular the automatic pilot or one of the human-machine interfaces with appropriate commands enabling the aircraft to be guided in lateral and vertical geographical planes (altitude and speed) so that the aircraft follows the reference trajectory provided for in the initial flight plan.

[0067] This various information from flight plan management is transmitted to the user, essentially by means of display devices or screens ("displays" according to the accepted Anglicism) which display the various piloting and navigation information.

[0068] The user can intervene in the management of the flight plan to modify it by means of different human-machine interfaces or "HMIs". These interfaces can be control stations of the "KCCU" type, an acronym meaning "Keyboard Cursor Control Unit" or of the "MCDU" type, an acronym meaning "Multi-Purpose Control and Display Unit". These different control stations generally comprise an alphanumeric keyboard, a system for controlling a graphic cursor and / or a display screen. It is also possible to use touch interface means arranged or not on the display screens of the dashboard.

[0069] The user of the system is generally the pilot of the aircraft. But the implementation of the method can be carried out within the framework of a ground station of an unmanned aircraft. In this case, the interactions and the display are ensured in the ground station and the corresponding choices are sent to the aircraft. The guidance is then carried out in the aircraft. Depending on the architectural choices, the trajectory can be calculated on the ground, and sent on board, or calculated on board and downloaded to the ground for display to the operator. Similarly, certain automatic adjustments can be carried out either at ground, or on board the aircraft.

[0070] Finally, this method can be implemented in air traffic control ground stations to guide the so-called "ATC" operator, an acronym meaning "Air Traffic Control" in the choice of instructions to give to the aircraft under his control, so as to optimize avoidance maneuvers or sequencing maneuvers in the aircraft arrival and approach procedures.

[0071] In the remainder of the text, the terms “pilot” or “user” are used interchangeably to designate the human operator who manages the flight of the aircraft.

[0072] The device of the invention comprises a trajectory securing module 104 interacting with a flight management system 102. The trajectory securing module is composed of a functional trajectory verification module 106 and a functional conflict resolution module 108.

[0073] The trajectory checker 106 has the general function of comparing a 4D trajectory calculated by a flight management system (trajectory with its safety corridor), with all the objects to be avoided during the flight on this trajectory. As will be detailed later, trajectory verification consists of checking whether a trajectory opens up a risk of conflict(s) with one or more objects.

[0074] To carry out the conflict risk checks, the trajectory checker is based on different reliable sources of data representative of the objects to be considered: for example the terrain, obstacles, weather information (weather radar on board or from a weather server). All the objects are represented and designated generically by a database (DB).

[0075] In the event of determining that there are one or more risks of conflicts with one or more objects, the trajectory checker 106 provides information on these conflicts, such as for example the nature of the conflict (air, terrain, etc.), the type of object, the location, the time, etc., to the conflict resolution module 108 (also referred to as a conflict resolver).

[0076] The conflict resolver 108 has the general function of implementing one or more conflict resolution algorithms, in particular vertical resolution algorithms (the vertical resolution is calculated by adapting the vertical profile by adding pseudo-constraints of altitude and / or speed), lateral resolution algorithms (the lateral resolution is calculated by a sequence of heading changes), mixed resolution algorithms (lateral and vertical), in order to propose a modified 4D trajectory which makes it possible to avoid identified conflicts.

[0077] The conflict resolver 108 operates iteratively in relation to the trajectory checker.

[0078] Any modified 4D trajectory is inspected by the trajectory checker 106 for determine whether it is indeed free of any conflict (whether there are residual conflicts or not).

[0079] Advantageously, the conflict resolution function implemented by the conflict resolver 108 applies a conflict resolution hierarchy along several axes.

[0080] A first axis of hierarchy is that of a hierarchy of conflicts by level of criticality, criticality which can be defined in different ways by the operator depending on his operational context.

[0081] In one embodiment, a classification of the conflicts is made according to a chronological order of encounter of the conflicts identified on a trajectory being verified.

[0082] In another embodiment, a classification of conflicts is made according to a level of danger and impact of the conflicts identified on a trajectory being verified.

[0083] In another embodiment, a classification of the conflicts is made with regard to the type of conflicts identified on a trajectory being verified,

[0084] Those skilled in the art may adapt other classifications of conflicts according to the context of application of the invention.

[0085] Another axis of hierarchization of conflict resolution is that of a hierarchy of algorithmic layers of resolution.

[0086] In one embodiment, the manner of prioritizing and combining the conflict resolution layers is configurable by the user via HMIs depending on the operational context. The user can define priorities and establish an order of sequence of the algorithms, he can define conditions for transition from one algorithm to another, via a configuration component and a conflict resolution manager.

[0087] In another embodiment, the configuration can be defined via a configuration file before the flight (or before commissioning if the operational context of the aircraft is well identified and is always the same).

[0088] Thus, conflict resolution can be done via one or more algorithmic layers: resolution in the lateral plane only, resolution in the vertical plane only, or resolution by combining all dimensions of the trajectory.

[0089] The resolution can also be determined by combining in a hierarchical manner a sequence of lateral resolution and vertical resolution (either lateral then vertical, or vice versa). The manner of combining or hierarchizing the resolution bricks is configurable and parameterizable, and it will be up to the user to determine the configuration best suited to his operational context as well as his performance constraints.

[0090] Another axis of hierarchization of the resolution is that of a hierarchy of modified trajectories generated by solving with the reference trajectory.

[0091] Indeed, following the determination of a first risk of conflict with a first object, a current trajectory which is modified could find itself in conflict with a second object which would be more impactful and for which there was no conflict with the initial unmodified current trajectory. In such a situation, the initial trajectory is then more relevant than the modified trajectory.

[0092] Depending on the number of algorithmic layers involved, there may be a certain number of intermediate trajectories which may prove relevant, in particular with regard to the prioritization of conflicts. Also advantageously, the conflict resolution function is configured to allow consideration and prioritization of one or more intermediate trajectories to determine a modified trajectory.

[0093] [Fig.2] represents a general synopsis of the different stages of the method of the invention in one embodiment.

[0094] The method 200 according to the invention is a method for securing a 4D trajectory.

[0095] In a set of embodiments of the invention, the method is executed to the occurrence of an event. It should be noted that the initial trajectory or reference trajectory with which the aircraft departs is a safe trajectory from start to finish in light of the contextual knowledge at the start.

[0096] Thus the occurrence of an event triggering a risk of conflicts and requiring the search for a secure trajectory according to the principles of the invention, can for example be a detection that the aircraft is outside a theoretical trajectory (which can be detected by a deviation in altitude from a reference vertical profile for example), or even a situation where air traffic control asks the pilot to deviate from his reference trajectory (for example in the terminal phase).

[0097] Thus, it is from changes in context (traffic, environment, etc.) or changes in the trajectory (diversion, breakdown, ATC request, pilot action, etc.) that potential conflicts may appear, requiring a search for a secure trajectory.

[0098] The method of the invention can also be triggered periodically in order to update a current trajectory with respect to new conditions (i.e. current aircraft position / altitude), the evolution of conflicts in the context of mobile conflicts (such as the weather for example).

[0099] Thus, the method is initiated on a so-called current 4D trajectory, which can be the reference trajectory calculated by a flight management system or a modified trajectory that the aircraft flies.

[0100] In one embodiment, the calculation of the reference 4D trajectory is carried out in a manner consistent with that done by an FMS (102 in [Fig.l]), integrating a trajectory lateral with an altitude and speed profile (as well as safety corridors).

[0101] The trajectory parameters are the current state of the aircraft (position, speed, altitude, fuel, etc.) and the flight plan (sequence of legs).

[0102] When the aircraft is removed from the procedure and the calculation context becomes a “join trajectory”, the initial point of the trajectory is then the aircraft position, and the end point is the last leg of the flight plan (generally, the destination airport). The trajectory then begins with a “joined part of the flight plan” to capture a leg of the flight plan.

[0103] From a lateral point of view, a flight management system produces a continuous trajectory which is a succession of straight and / or curved segments making it possible to connect the points of the flight plan with lateral transitions calculated according to a planned speed profile.

[0104] From a vertical point of view, the vertical profile is based on the construction of a theoretical climb, cruise and descent profile. These profiles calculated by the FMS consist, among other things, of speed and altitude profiles optimized according to the aircraft performance and respecting all the constraints contained in the ARINC 424 procedures inserted in the flight plan.

[0105] The 4D trajectory is accompanied by a lateral and vertical safety corridor which can correspond to the position inaccuracy (typically the EPU “Estimated Position Uncertainty” lateral error and the “Vertical Deviation” vertical error for the current position) and to the position inaccuracy tolerated downstream of the aircraft (typically the RNP “Required Navigation Performance” on the lateral and the VPPL “Vertical Path Performance Limit” on the vertical plane).

[0106] The 4D trajectory calculated by the flight management system and all the associated information are provided to the trajectory securing module (104 in [Fig.l]), which is external to the flight management system, and which will implement a conflict resolution procedure by a sequence of trajectory securing steps 204, before providing 214 to the flight management system the parameters associated with a secured 4D trajectory.

[0107] In more detail, the trajectory securing steps will consist of checking 206 whether a 4D trajectory conflicts with objects or elements (at least one object), then resolving iteratively and by implementing a conflict resolution procedure, the potential conflicts, until a secure 4D trajectory is retained (214), i.e. determining a solution or a hierarchical list of solutions with conflict avoidance parameters allowing the flight management system to construct a secure 4D trajectory.

[0108] The conflict avoidance parameters can be of different natures depending on what the trajectory calculator is capable of processing. It can be provided by example a list of points where a change of heading is planned (with its associated heading) or a list of points where a change of speed is planned, or a list of safety altitudes (i.e. pseudo-constraints).

[0109] The method makes it possible, with information calculated by the flight management system regarding the altitude, time and position on each segment of the flight plan, to check whether a calculated 4D trajectory conflicts with at least one element.

[0110] The data used are not limited, and the method can take into account, for example, additional data regarding a tactical situation (“go / nogo” zones, threat zones, etc. in military cases), data on prohibited air zones, restricted access zones or zones unsuitable for the navigation class authorized for the aircraft. The limit of the data used is only set by the existence of such data and by the capacity of the device to consume a data source.

[0111] Step 206 of verifying the existence of a conflict makes it possible to indicate the type of conflict (aerial, terrain, etc.), the location of the object, and also to give additional information linked to the conflict, such as, for example, indicating a safety altitude that should be respected in the event of a terrain conflict.

[0112] In one embodiment, margins for performing these calculations may be defined statically or dynamically.

[0113] A margin corresponds to an authorized safety corridor (laterally and vertically) around the trajectory. It can be defined and configured statically, either as a given value for any type of conflict, or as a given value for each type of conflict (one value for weather conflicts, one value for terrain, ...).

[0114] A margin can be defined dynamically, starting from a 'nominal' value and moving to reduced margins in certain degraded cases (for example, failure cases, low fuel), where a slightly higher risk is authorized but which potentially makes it possible to obtain other trajectories, and potentially shorter ones (and thus make it possible to land the aircraft with the remaining fuel). If there is no conflict identified, the method makes it possible to inform 214 the flight management system that the calculated 4D trajectory is safe, and that the aircraft can fly it.

[0115] If conflicts are identified, the method continues with an iterative sequence of steps of conflict resolution (208), generation by the flight management system of modified intermediate trajectories (210), and verification of the modified 4D trajectories (212) until a conflict resolution is achieved or a safe trajectory is selected that satisfies the conflict resolution.

[0116] The conflict resolution step 208 can be implemented according to different embodiments which can be parameterized, configured by the user (via the configurator of the resolution module 108).

[0117] The conflict resolution step makes it possible to calculate by the computer (104) external to the flight management system, a hierarchical set of solutions with their conflict avoidance parameters, allowing the aircraft to avoid a conflict with at least one identified object. The conflict avoidance parameters are obtained and hierarchized by the implementation of conflict resolution algorithm(s).

[0118] In one embodiment, the conflict resolution procedure is carried out according to a so-called staged approach of mobilizing lateral and vertical resolution algorithms, and where the user establishes the order and conditions for moving from one algorithm to another.

[0119] In an operational framework where vertical avoidance is preferred to horizontal avoidance, and where it is set as a condition not to go up during a descent phase for example, a tiering of the solicitation of the conflict resolution algorithms is illustrated as an example with [Fig.3].

[0120] Those skilled in the art will understand that [Fig. 3] is an example applied to a descent phase, but that the principles described are applicable to various other flight phases, and more generally applicable to any phase of altitude change occurring during climb, cruise, descent or approach.

[0121] For example, the principles of the invention applied during a leveling off during the climb phase may prove effective in avoiding cross traffic. Thus, [Fig. 3] represents a block diagram 300 of a staged conflict resolution step, which seems particularly suited to terrain conflict avoidance, where the method, after having determined 302 the existence of a conflict, continues with a step 304 to determine whether the aircraft is in the descent phase.

[0122] If yes, the method makes it possible to check the current altitude of the aircraft, and determine whether this current altitude is higher or lower than a safety altitude given for this conflict during the previous conflict verification step.

[0123] If the aircraft is at an altitude lower than the safety altitude (i.e. conflict altitude with margin), the method allows in a following step 312 to request a lateral resolution algorithm.

[0124] If the aircraft is at an altitude higher than the safety altitude, the method allows in a following step 308 to request a vertical resolution algorithm.

[0125] Returning to step 304 of determining the current phase in which the aircraft is located, if the latter is not in a descent phase, the method makes it possible to request 308 a vertical resolution algorithm.

[0126] After the vertical resolution step 308, the method makes it possible to check 310 whether or not there are conflicts with the trajectory modified according to the vertical resolution.

[0127] If there is no conflict, the resolution process ends.

[0128] If there is a conflict, the method allows in a following step 312 to request a lateral resolution algorithm.

[0129] An example of conflict resolution prioritization is shown, which is not limiting, and those skilled in the art will be able to customize the conflict resolution module according to other configurations.

[0130] An alternative embodiment consists of carrying out all possible resolutions (lateral, vertical, mixed) and choosing a posteriori according to criteria allowing the solution trajectories corresponding to said resolutions to be directly prioritized. In the example of [Fig.3], the criterion is set upstream (flight phase and aircraft altitude versus conflict altitude). In this case, the criterion is that we wish to favor vertical avoidance, except in the descent phase where we are prohibited from going up.

[0131] This type of hierarchy can be applied for field conflict avoidance. Thus the test of step 302 is a classic conflict verification, while the test of step 306 is an algorithmic hierarchy criterion adapted to the situation.

[0132] Thus, in another embodiment, the conflict resolution step is configured to implement an algorithm working directly in all dimensions of the trajectory, such as for example a so-called “n-Dimensional white cane” algorithm, where a user can configure certain elements of the algorithm, such as the weight to be given to certain dimensions or he can let the algorithm make its own choices.

[0133] An n-Dimensional white cane algorithm is based on a principle of angular scanning and stepping for each dimension of a trajectory. This type of algorithm resolves a conflict by allowing 'step-by-step' advancement towards a flight plan to be joined, through a series of maneuvers.

[0134] An example of a solution method according to a white cane algorithm is described in more detail with reference to [Fig.7].

[0135] According to various embodiments, the white cane algorithm may be bounded or not, generalized or not in a higher level solver, depending on the computational platform envisaged and depending on the functional constraints which are given (response time, computational resources, complexity / volatility of the trajectory, etc.).

[0136] Returning to [Fig.2], when the modified 4D trajectory verification step 212 confirms that there is no longer a conflict, the trajectory securing method ends, and the set of avoidance parameters relating to a safe 4D trajectory is provided 214 to the flight management system to construct a safe trajectory that can be flown as a standard calculated trajectory.

[0137] In the event of a residual conflict identified during the 4D trajectory verification step 212, a message may be raised to inform the aircraft crew.

[0138] In an alternative embodiment, the device of the invention can be coupled to a system which takes over in the event of residual conflict with a servo-controlled guidance on the trajectory, so as to never have an unflyable trajectory associated with the active flight plan.

[0139] Advantageously, the security method of the invention allows the automatic triggering of a conflict resolution algorithm regardless of the flight phase.

[0140] The triggering of the conflict resolution can occur after each trajectory calculation (i.e. in the context of a classic FMS, on each pilot action or on a periodic refresh or on an external event of the trajectory).

[0141] In a variant, for performance reasons, the triggering of the method can be limited only to times when the aircraft is at a certain distance from the trajectory, the distance being able to be parameterized.

[0142] [Fig.4] represents a block diagram of a method 400 for securing a 4D trajectory during a descent phase of an aircraft.

[0143] The method begins by taking into account (i.e. upon receipt by the trajectory securing module) 402 a 4D trajectory calculated by an FMS of the aircraft, the trajectory comprising a vertical descent profile and possibly altitude constraints if they are defined in the arrival procedure.

[0144] An FMS constructs a vertical trajectory taking into account the aircraft's performance as well as the parameters of the procedures inserted in the flight plan. These procedures can be defined with regard to the ARINC 424 standard and can contain altitude constraints associated with navigation points.

[0145] Altitude constraints can be of several types (the applicable aeronautical standards determine the tolerances required by aircraft types, navigation airspace classes, and possibly other criteria): - “AT” constraint: the aircraft must be at the altitude associated with the constraint at the point where the constraint is defined; - “AT or ABOVE” constraint: the aircraft must be at or above the altitude associated with the constraint at the point where the constraint is defined; - “AT or BEL0W” constraint: the aircraft must be below or at the altitude associated with the constraint at the point where the constraint is defined; - “WIND0W” constraint: combination of an “AT OR ABOVE” constraint and an “AT OR BELOW” constraint.

[0146] The present invention makes it possible to re-exploit the notion of altitude constraint, initially static by definition of the procedures, into a dynamic input from the trajectory securing device.

[0147] Thus, safety altitudes determined by the 4D trajectory safety device are transformed into altitude constraints and injected into the inputs of the FMS vertical trajectory calculation algorithm.

[0148] Returning to the example of [Fig.4], after calculating a vertical descent profile with possible altitude constraints, the method allows in the following step 404 to verify, by the computer external to the FMS, the trajectory with respect to a set of obstacles (terrain, weather, etc.) and to generate a list of conflicts, identifying for each type of conflict avoidance parameters, such as for example a safety altitude allowing the aircraft to avoid an obstacle.

[0149] In the event of conflict(s), the method makes it possible to integrate 406 all of the safety altitudes as “pseudo-constraints” in the list of altitude constraints for the FMS calculations.

[0150] For example, on a 4D descent trajectory initially calculated by an FMS, A and B are two points having AT altitude constraints. After analyzing and resolving potential conflicts, the safety device calculates a safety position and altitude to avoid a terrain conflict. The method makes it possible to address the calculated safety position and altitude parameters to the FMS to restart the calculation of a 4D trajectory by integrating these avoidance parameters in the form of a “pseudo-AT or ABOVE altitude constraint”, or a “virtual altitude constraint” (the altitude not being derived from the published A424 procedure).

[0151] The method then operates a loop of steps. Indeed, adding constraints modifies the altitude and speed at a point, and therefore modifies the turning radius on the trajectory at that point. The lateral trajectory can then be modified and new conflicts can be detected.

[0152] Also, the method makes it possible to verify whether a modified trajectory which is calculated by the FMS with avoidance parameters calculated by the conflict resolution module presents new conflict risks or not.

[0153] When several conflicts are detected, the method makes it possible to create as many sets of avoidance parameters with pseudo-constraints and constraints to be respected, and makes it possible to provide them to the FMS for as many intermediate trajectory calculations.

[0154] In a following step 408, the FMS vertical trajectory construction algorithms will take into account the altitude pseudo-constraint(s) in the same way as conventionally published altitude constraints, in order to perform a calculation of a modified 4D trajectory for the descent phase.

[0155] In a following step 410, the method makes it possible via the trajectory securing device to verify the modified 4D trajectory, and to determine 412 whether it is free of any conflict or not.

[0156] In a variant, a maximum number of iterations is defined to converge a modified trajectory, and the method can also check whether the maximum number of iterations is reached or not to complete the convergence process, and provide 414 a secure 4D trajectory.

[0157] In one embodiment, in order to warn the crew that the vertical profile of descent has been modified, an indication is added along the modified trajectory displayed on a navigation display (ND) in the form of a symbol called a “pseudo navigation point” or “pseudo-waypoint” in English, as illustrated in [Fig.5] where a pseudo-waypoint 502 is positioned as a characteristic waypoint, along the trajectory displayed on a display (ND) 500.

[0158] It is known that several types of “pseudo-waypoint” can be calculated by an FMS, such as: a descent start point, a speed change point, a flap extension point, etc. However, there is no “pseudo-waypoint” that is calculated and displayed on a navigation map, this only having meaning in the context of input / output data of a trajectory calculation.

[0159] In one embodiment, the method is applied when the aircraft operates in a guidance mode known as managed mode, where the position of the aircraft is controlled on a horizontal trajectory and a vertical reference profile. In the managed mode, the FMS determines the descent hypotheses, the aircraft is controlled on the route, and guidance laws are applied to the aircraft so that it follows the route step by step.

[0160] In another embodiment, the method is applied when the aircraft is operating in a guidance mode known as a selected mode. The descent hypotheses are then those chosen by the crew, until the altitude authorized by air traffic control is reached ("clearance altitude").

[0161] In this case, the pseudo-constraints are not taken into account because the FMS does not have authority over the descent hypotheses. However, and advantageously, the method of the invention which allows the creation of pseudo-constraints, can be applied in selected mode because it allows the pilot to be informed about the zone and altitude of a conflict. The zone where the trajectory is in conflict is then displayed as well as the pseudo-waypoint indicating the safety altitude which should be adopted.

[0162] [Fig.6] illustrates for a descent phase in selected mode, a display on a navigation screen 600 of an aircraft, a conflict zone 602 and a detected conflict point 604.

[0163] Using these indications, the crew can then 'manually' resolve the conflict by adapting its descent instructions. It can also engage 'managed' mode to give the FMS the authority to automatically follow the safe descent profile in the manner described above.

[0164] In an alternative embodiment, an alert can be raised when the aircraft is about to descend below a conflict altitude, even well downstream of the current position, knowing that the system does not anticipate being able to climb back up during a descent or approach phase towards an airport. Thus, once below this altitude, there is no longer of possible vertical correction, and the conflict will occur later (without additional manual corrective action or by switching to a resolution in the lateral plane which will inevitably lead to an increase in flight time and fuel consumption).

[0165] In another alternative embodiment, automation of conflict avoidance in cases of pilot incapacitation may be implemented. For example, without pilot action following an alert message within a certain time period, automatic engagement of the 'managed' mode may be activated to give the FMS authority to follow the safe descent profile in the manner described above.

[0166] [Fig.7] represents a synopsis of different stages of lateral conflict resolution in an embodiment of the invention implementing a “white cane” type algorithm.

[0167] The general principle of a white cane algorithm consists of a series of calculations allowing iteratively returning to the initially flown flight plan.

[0168] In the case where a trajectory solution proposed by an FMS, on the basis of a heading instruction, presents a conflict identified by the device of the invention, a white cane type lateral resolution algorithm 700 may consist of a sequence of steps which consists mainly in a first step 702 of establishing an angular scan from a heading instruction [heading instruction + / - X °], in steps of alpha degrees.

[0169] In a following step 704, the method makes it possible to calculate a set of joining trajectories between the aircraft and the flight plan, on the basis of the headings established in the previous step by the angular scanning.

[0170] A following step 706 consists of checking for the presence of conflicts on all the joining trajectories, then the method allows 708 to retain the valid trajectory which presents the smallest angular deviation from the current instruction.

[0171] The method ends 710 by proposing the retained heading instruction to the pilot for engaging the trajectory.

[0172] The white cane algorithm can be adapted to explore the space in a series of lateral maneuvers (i.e. heading changes). The maximum number of maneuvers, and the angular space to be scanned for each maneuver can be configurable (fixed before takeoff; configured by the operator (pilot)). The advantage of this approach is to limit any proposed solution to a series of actions that can be reasonably calculated by a certified on-board system and carried out by an automated system, or executed by a pilot.

[0173] Various higher-level resolution modes (i.e. a sort of “meta-resolution”) can be adapted, being bounded or unbounded, based on “brute force” exploration, stochastic, fuzzy logic, genetic algorithms, etc. The only constraint to an implementation variant is the ability to converge to at least one solution, and the adequacy of a response time to a functional chain.

[0174] In one embodiment, the lateral conflict resolution may be based on an "n-Dimensional white cane" type algorithm. This algorithm is based on the same principle of scanning and stepping as the simple white cane algorithm described with reference to [Fig.7], but it is extended to each dimension of the trajectory.

[0175] Thus, in one embodiment, the sequence of steps consists of a first step of determining maneuvers to be performed, a maneuver being defined by a pair (Heading, FPA), where the parameter Heading designates a heading instruction and the parameter FPA (“Flight Path Angle”) designates an angle in the vertical plane of the flight path between the speed vector and the local horizon. The performance of a maneuver covers: a lateral angular scan [heading instruction + / - X°] around a current heading instruction, in steps of “alpha” degrees, and a vertical angular scan [current FPA + / - X°] around a current FPA angle, in steps of “alpha” degrees. The alpha parameter is calculated from the performance of the aircraft, its current situation (altitude, speed, roll), bounded by the flight envelope.

[0176] A next step allows calculating a piece of trajectory corresponding to each maneuver.

[0177] Another step consists of checking for the presence of conflicts on all possible maneuvers.

[0178] Then the algorithm makes it possible to select the valid maneuver which presents the smallest angular deviation from the current setpoint or the smallest angular deviation from the current FPA (the weight of the choice being configured by the operator according to the operational context).

[0179] As with the simple algorithm, the n-dimensional algorithm can be bounded or not, generalized or not in a higher level solver, depending on the computational platform envisaged, and the functional constraints that exist (response time, computational resources, complexity / volatility of the trajectory, etc.).

[0180] In one embodiment, the conflict resolution may be a multi-dimensional resolution based on a “graph traversal” type algorithm.

[0181] Figures 8a and 8b illustrate an embodiment of an n-dimensional conflict resolution of the “graph traversal” type according to the invention.

[0182] The n-dimensional conflict resolution algorithm relies on the use of a graph traversal method, such as the known algorithm “A*”, which is a path finding algorithm in a graph between an initial node and an end node, which uses a heuristic evaluation on each node to estimate the best path passing through it, and then visits the nodes in order of this evaluation. heuristic.

[0183] In contrast, the algorithm implemented for n-dimensional conflict resolution within the meaning of the invention imposes in the vertical plane an evolution which is guaranteed to be flyable, in order to avoid a truly 3D search which is very costly in terms of response time.

[0184] Thus, for example, in the top diagram of [Fig.8a], a conflict zone is represented which has been identified by a conflict verification step, on the portion of the aircraft's trajectory, between points A and B.

[0185] The conflict resolution algorithm by graph traversal, allows to map the conflict zone on a terrain elevation grid illustrated on the bottom of [Fig.8a]. The terrain elevation grid gives the minimum altitudes to be able to enter each "cell", such as an altitude of 6200 for the cell corresponding to point B, or an altitude of 5800 for the cell corresponding to point A.

[0186] The algorithm then makes it possible to search for a path constructed backwards from the end of the conflict (i.e. point A) and leading to the aircraft via the start of the conflict (i.e. point B), in order to keep the current instruction of the aircraft as much as possible. This is illustrated in [Fig.8b], representing the safe trajectory proposed to avoid the conflict.

[0187] The vertical conflict avoidance profile is shown at the top, starting from the exit point (Exit Point) at altitude 5800, then going back, a first point 1 at altitude 6000, a second point 2 at altitude 6300, an entry point (Entry Point) at altitude 6600, and the current position point of the aircraft (A / C) at altitude 6800).

[0188] The lower part of [Fig.8b] shows a representation on the elevation grid of the safe trajectory which is calculated.

[0189] Traversing the graph by imposing this profile makes it possible to find a safe path at altitude.

[0190] According to one embodiment, the conflict resolution algorithm for the vertical plane can, during this backward resolution, apply a criterion of the fastest possible climb to the aircraft altitude, in order to authorize as many “cells” as possible. Indeed, the faster the climb, the more cells there will be to choose from when moving from one cell to a neighboring cell.

[0191] According to another embodiment, the conflict resolution can be done by choosing a strategy based on speed, using parameters of the “conflict time” type provided by the trajectory checker (104). This is particularly applicable if the conflict is mobile or temporary. Thus, advantageously, the calculation and presentation in the cockpit of a secure continuous 4D trajectory free of any conflict, allows a crew to lighten its workload, by offering it at any time a trajectory on which it can engage to land. The secure trajectory can be sent to the ground in order to facilitate exchanges with the on-board and anticipate its automatic monitoring in the event of pilot incapacity, for example in an SPO world (acronym for “Single Pilot Operation” in English).

[0192] The method of the invention can be implemented using hardware and / or software elements. The method can be available as a computer program product on a computer-readable medium. The method can be implemented on a system that can use one or more dedicated electronic circuits or a general-purpose circuit. The technique of the method according to the invention can be carried out on a reprogrammable computing machine (a processor or a microcontroller for example) executing a program comprising a sequence of non-transitory instructions, or on a dedicated computing machine (for example a set of logic gates such as an FPGA or an ASIC, or any other hardware module). The different modules of the system according to the invention can be implemented on the same processor or on the same circuit, or distributed over several processors or several circuits.The modules of the system according to the invention consist of computing means including a processor. The reference to a computer program which, when executed, performs any of the functions described above, is not limited to an application program running on a single host computer, but may be executed by one or more processors.

Claims

Claims

1. Method for calculating a safe 4D trajectory for an aircraft comprising the following steps: - determining (206), by a computer (104) external to a flight management system of the aircraft, whether on a current 4D trajectory calculated by the flight management system, there exists for the aircraft a risk of conflict with at least one object; - if there is no risk of conflict, defining the current 4D trajectory as being a safe trajectory for the aircraft; or - if there is a risk of conflict: - calculating (208), by the computer (104) external to the flight management system, a hierarchical set of solution trajectories with their conflict avoidance parameters, allowing the aircraft to avoid a conflict with said at least one object, said conflict avoidance parameters being obtained and hierarchical by implementing a conflict resolution procedure;- calculating (210), by the flight management system of the aircraft, a modified 4D trajectory from the conflict avoidance parameters provided by the computer (104) external to the flight management system; and - determining (212) by the computer (104) external to the flight management system, whether on the modified 4D trajectory, there exists for the aircraft a new risk of conflict with at least one other object; - if there is no risk of conflict, defining the modified 4D trajectory as being a safe trajectory for the aircraft; or - if there is a risk of conflict, repeating the previous steps until a conflict resolution is achieved.;

2. Method according to claim 1 in which the step of determining the risk of conflict by the computer (104) external to the flight management system, comprises steps consisting of identifying from different data sources, at least the presence of fixed or moving obstacles on the current or modified 4D trajectory, and of verifying whether the obstacle(s) can generate a conflict with the aircraft.

3. Method according to claims 1 or 2 in which the step of determining the risk of conflict by the computer (104) external to the flight management system, further comprises a step of generating a list of conflicts identifying for each type of conflict conflict avoidance parameters.

4. A method according to claim 3 wherein the conflict avoidance parameters are safety altitudes and / or heading values ​​and / or speed values.

5. Method according to any one of the preceding claims in which the step of determining the risk of conflict by the computer (104) external to the flight management system, further comprises steps consisting of determining the current flight phase of the aircraft and determining the corresponding conflict resolution procedure.

6. A method according to any preceding claim wherein the step of implementing a conflict resolution procedure comprises implementing one or more conflict resolution algorithms among vertical resolution, lateral resolution or mixed resolution algorithms.

7. Method according to any one of the preceding claims in which the step of implementing a conflict resolution procedure consists of implementing a sequence of several conflict resolution algorithms, the sequence being predefined or configurable.

8. Method according to any one of the preceding claims in which the step of implementing a conflict resolution procedure consists of taking into account one or more intermediate trajectories calculated during the iteration phase.

9. Computer program product comprising code instructions for carrying out the steps of the method for calculating a secure 4D trajectory for an aircraft according to any one of method claims 1 to 8, when said program is executed on a computer.

10. Device for calculating a secure 4D trajectory for an aircraft, the device comprising means configured to implement the steps of any one of claims 1 to 8 of the method for calculating a secure 4D trajectory for an aircraft.

11. Flight management system for aircraft comprising means for operating with a device for calculating a secure 4D trajectory for aircraft according to the preceding claim.

12. Aircraft comprising a flight management system according to the preceding claim.

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