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. Conflict resolution results in a hierarchical list of solution trajectories. This list 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 safe 4D trajectory for an aircraft technical field

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

[0002] Flight management systems or flight managers, known by the generic term "Flight Management System" (FMS), offer pilots 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 era in particular).

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

[0005] The navigation database or "Navigation DataBase" (NDB) contains all the information necessary for the preparation and monitoring of the flight plan, including in particular: air routes ("Airways" according to the known anglicism); waypoints or waypoints ("Waypoints" according to the known anglicism); airports and their various runways; approach procedures ("Standard Arrival" or (STAR) according to the known anglicism), and departure procedures ("Standard Instrument Departure" or (SID) according to the known anglicism); other information concerning ground facilities.

[0006] A flight plan consists of a series of waypoints whose structure is defined by standard norms. These points are linked by segments (a segment or "leg" being defined as a unit portion of the flight plan joining a final condition according to a maneuver specified by the leg type, the leg types 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 visualization 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 of the flight plan, the estimate of the amount of fuel on board, etc.

[0008] The results of calculations performed by an FMS computer as well as 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 because it considers all the aircraft's positions in three spatial dimensions, with each position having a time reference. A 4D trajectory is a sequence of points describing the vertical, lateral, and longitudinal profiles of an aircraft's flight. Each point is described by three position coordinates (e.g., latitude, longitude, and altitude) and one time coordinate.

[0010] Some FMS systems 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 commands sent by the FMS). In both cases, the guidance system provides the information necessary to follow this trajectory (speeds, angles, altitude, target speed, etc.), and may even take over some of the actions to be performed.

[0011] In flight, one of the main tasks of a flight management system is the precise determination of the aircraft's location. 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 key component of the avionics of a modern aircraft, its task being to reduce the crew's workload in flight planning, performance management, aircraft piloting, flight parameter measurement, and navigation. Thus, the FMS is able to control the entirety of a flight, from takeoff to landing, by performing all the necessary calculations through a flight management computer (FMC).

[0013] As long as the aircraft follows a published procedure, it is assured of being protected. However, for various reasons (air traffic control, weather), the aircraft may find itself off the theoretical trajectory, requiring a return to it in the short or long term. These non-nominal situations are very frequent, and avionics products are rather poorly suited to them. In particular, no indication exists to help a crew assess its situation with regard to a potential terrain / weather conflict on a return trajectory to the initial flight plan. In cases where these trajectory deviations are managed manually by the pilot by setting a heading, no return trajectory is calculated and the portion joined is even less verified with respect to a possible terrain conflict.

[0014] Thus, when a trajectory calculated by an FMS passes through areas considered unsafe, for example outside of a published procedure, the FMS does not have the native ability to propose a trajectory that 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 arise when air traffic control requests the pilot to deviate from their reference trajectory, for example, during the terminal phase. In this operational scenario, most known FMS systems do not implement a function for calculating the return trajectory to the initial flight plan, thus leaving the pilots and air traffic control with the responsibility for navigation, with very limited information available in the cockpit.

[0016] Each stakeholder creates their own mental representation of rejoining 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 workload of the pilots.

[0017] Proposals exist for calculating a flight plan return trajectory. Applicant's patent applications FR3031175 Bl, FR3051057 Bl, and FR3064351 B1 are examples of flight plan return trajectory calculations, respectively for a lateral return, a vertical return, and a delayed return. In these solutions, the flight plan return trajectory is always calculated under a simplified assumption from the aircraft's current position, which may make it potentially unsuitable for an immediate return to the flight plan (because it is unsafe or generates a conflict due to an obstacle or a possible energy management problem), or which may sometimes lead to a return to an active segment that is no longer operationally relevant.

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

[0019] However, currently nothing guarantees in the construction of a permanent joining trajectory that it will not come into conflict with terrain or weather obstacles.

[0020] Therefore, assistance from a computer in an aircraft's flight management system would be desirable. However, such assistance must be able to ensure that the automatically constructed return trajectory does not cross any fixed or moving obstacles (terrain, weather, air traffic, or prohibited airspace), i.e., that it is safe.

[0021] However, there is currently no solution enabling the construction by a computer of a flight management system 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 safety increases the workload of pilots, who must cross-reference the various information available to them: the view from outside the cockpit; air traffic control instructions (e.g., heading, altitude, speed, etc.); weather radar information (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 may be occupied by aircraft; and information from warning systems.

[0023] Furthermore, in a context of reducing the number of pilots on board, with the emergence of Single Pilot Operations (SPO) concepts or Remotely Piloted Aircraft Systems (RPAS), it is necessary to minimize the workload of the flight operator (pilot, remote pilot), as well as that of the air traffic controller, particularly during complex flight phases such as the approach. It is also important to cover cases of incapacitation of the sole pilot on board, an event whose occurrence does not preclude its exclusion from safety analyses.

[0024] Various systems have been developed to warn a crew of the risk of a collision with the ground and thus help them manage navigational safety. Some, such as TAWS (Terrain Awareness and Warning System), make a short-term trajectory prediction for the aircraft based on current flight information (position, heading, orientation, and velocity vector magnitude) provided by onboard equipment, and compare it to a map of the area being overflown (extracted from an onboard terrain elevation database). They can issue warnings to the aircraft crew whenever the short-term predicted trajectory collides with the terrain. These are aid and warning solutions that operate on a short timescale, on the order of 3 minutes ahead of the aircraft.They are designed to provide a tactical "reactive" solution, and generally 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 system of Navigation does not allow anticipation of a terrain conflict that would take place further down 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 gathered, air traffic control personnel and the pilot work together to manually select a new route after analysis.

[0027] These systems provide guidance and assistance. However, there is no system that constructs a strategic trajectory, i.e., with a longer lead time (of at least 10 minutes ahead of the aircraft), that is secure.

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

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

[0030] One object of the invention is thus to overcome the shortcomings of the prior art by proposing a process leading to the automatic construction of an alternative 4D trajectory, safe from any type of conflict.

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

[0032] In one embodiment, the crew can choose to automatically control the aircraft on the alternative trajectory, and engage 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 area, ...).

[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).

[0035] In a context (SPO) (“Single Pilot Operations” according to the established anglicism), the present invention significantly reduces the workload of the pilot and allows the system, in the event of pilot incapacity, to land the aircraft autonomously and safely.

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

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

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

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

[0040] The invention can preferably be used in conjunction with an FMS-type flight management system. 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 environment, to secure the reference trajectory of an aircraft, in order to allow, for example: - loading a conflict-free trajectory into an on-board trajectory computer such as an FMS; - display in an EFB (“Electronic Flight Bag”) via trajectory securing applications; - implementation in ground-based tools usable by air traffic control; - implementation in ground tools usable by an airline control center with the possibility of exporting to an onboard flight management system.

[0043] To obtain the desired results, a method for calculating a safe 4D trajectory for an aircraft is proposed. The method comprises the following steps: - determining, by a computer external to the aircraft's flight management system, whether, on a current 4D trajectory calculated by the flight management system, there is a risk of the aircraft encountering 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: - calculate, 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 hierarchized by the implementation of a conflict resolution procedure; - calculate, using the aircraft's flight management system, a modified 4D trajectory based on 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, if 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 offers 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, includes 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 checking whether the obstacle or obstacles 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 includes 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 includes 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 from 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 safe 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 safe 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 safe 4D trajectory for an aircraft according to the invention.

[0055] The invention also relates to a computer program comprising code instructions for carrying out the steps of the method for calculating a safe 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 from the following description in relation to the following drawings.

[0057] Fig. 1 represents a synoptic diagram of the device of the invention interacting with an aircraft flight management system;

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

[0059] Fig. 3 represents a synoptic diagram of the steps for the staged resolution of conflicts, in one embodiment of the invention;

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

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

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

[0063] Figure 7 represents a synoptic diagram of lateral conflict resolution steps in an embodiment of the invention;

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

[0065] Figure 1 shows a schematic diagram of the device 100 of the invention interacting with an aircraft flight management system. The flight management system 102, whose main function is to manage a specific 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. Based on information from the flight plan and certain information from the aircraft's sensors (localization systems, autopilot), flight plan management consists of continuously calculating the aircraft's trajectory and developing a number of predictions. A prediction is understood to be 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 might be the remaining flight time until the aircraft lands or the maximum flight distance given the fuel reserves. Trajectory calculations and predictions are used to develop aircraft guidance, with guidance information being incorporated into flight plan management.

[0066] The guidance function provides, in particular, the autopilot or one of the human-machine interfaces with appropriate commands to guide the aircraft in lateral and vertical geographical planes (altitude and speed) so that the aircraft follows the reference trajectory planned in the initial flight plan.

[0067] These various pieces of information from the flight plan management are transmitted to the user, mainly by means of visualization devices or screens ("displays" according to the established anglicism) which display the various piloting and navigation information.

[0068] The user can interact with and modify the flight plan using various human-machine interfaces (HMIs). These interfaces can be keyboard cursor control units (KCCUs) or multi-purpose control and display units (MCDUs). These control units generally include an alphanumeric keyboard, a graphical cursor control system, and / or a display screen. Touchscreen interfaces, whether or not integrated into the instrument panel displays, can also be used.

[0069] The system user is generally the aircraft pilot. However, the method can be implemented within the framework of a ground station of an unmanned aircraft. In this case, the interactions and display are provided at the ground station. The corresponding choices are then sent to the aircraft. Guidance is then performed on board. Depending on the architecture choices, the trajectory can be calculated on the ground and sent to the aircraft, or calculated on board and downloaded to the ground for display to the operator. Similarly, certain automatic adjustments can be made either on the ground or on board the aircraft.

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

[0071] In the rest of the text, the terms "pilot" or "user" are used interchangeably to refer to the human operator who manages the flight of the aircraft.

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

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

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

[0075] If it is determined that there are one or more risks of conflict with one or more objects, the trajectory checker 106 provides information on these conflicts, such as the nature of the conflict (aerial, ground, ...), the type of object, the location, the time, etc., to the conflict resolution module 108 (also referred to as the conflict solver).

[0076] The conflict solver 108 has the general function of implementing one or more conflict resolution algorithms, including 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 course changes), mixed resolution algorithms (lateral and vertical), in order to propose a modified 4D trajectory that avoids identified conflicts.

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

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

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

[0080] A first axis of prioritization is that of a prioritization of conflicts by level of criticality, criticality being able to be defined in different ways by the operator according to its operational context.

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

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

[0084] A person skilled in the art may adapt other conflict classifications according to the context of application of the invention.

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

[0086] In one embodiment, the way in which conflict resolution layers are prioritized and combined is configurable by the user via GUIs according to the operational context. The user can define priorities and establish a sequence order for the algorithms, and can define conditions for switching 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 hierarchically combining a sequence of lateral and vertical resolutions (either lateral then vertical, or vice versa). The way in which the resolution blocks are combined or hierarchized is configurable and parameterizable, and it will be up to the user to determine the configuration best suited to its operational context and performance constraints.

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

[0091] Indeed, following the identification of an initial risk of conflict with a first object, a current trajectory that is modified could find itself in conflict with a second object that would have a greater impact and for which there was no conflict with the initial, unmodified 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 several intermediate paths that could prove relevant, particularly with regard to conflict prioritization. Advantageously, the conflict resolution function is configured to allow for the consideration and prioritization of one or more intermediate paths to determine a modified path.

[0093] Figure [Fig.2] represents a general overview of the different stages of the process 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 carried out in the event of an occurrence. It should be noted that the initial trajectory or reference trajectory with which the aircraft departs is a safe trajectory from beginning to end with regard to the contextual knowledge at departure.

[0096] Thus, the occurrence of a triggering event that risks conflicts and requires the search for a safe 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 difference in altitude with a reference vertical profile for example), or 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 trajectory (diversion, failure, ATC request, pilot action, etc.) that potential conflicts can appear, requiring a search for a safe 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 weather for example).

[0099] Thus, the process 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 accordance with that done by an FMS (102 in [Fig.1]), integrating a lateral trajectory 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,...) and the flight plan (sequence of legs).

[0102] When the aircraft is removed from the procedure and the calculation context becomes a "rejoining trajectory", the starting point of the trajectory is then the aircraft position, and the ending point is the last leg of the flight plan (generally, the destination airport). The trajectory then begins with a "rejoining portion 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 allowing the points of the flight plan to be connected 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 aircraft performance and respecting all the constraints contained in the ARINC 424 procedures included 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 lateral error EPU “Estimated Position Uncertainty” and the vertical error “Vertical Deviation” for the current position) and the tolerated position inaccuracy 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 associated information are provided to the trajectory securing module (104 in [Fig.1]), 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 secure 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 the potential conflicts iteratively by implementing a conflict resolution procedure, until a trajectory is selected (214). 4D secure, i.e. determine a solution or a list of hierarchical solutions with conflict avoidance parameters allowing the flight management system to construct a 4D secure trajectory.

[0108] The conflict avoidance parameters can be of different kinds depending on what the trajectory computer is capable of processing. For example, it can provide 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 even a list of safety altitudes (i.e., pseudo-constraints).

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

[0110] The data used is not limited, and the method may take into account, for example, additional data concerning a tactical situation (go / no-go zones, threat zones, etc. in military cases), data on prohibited airspace, restricted access, or airspace unsuitable for the aircraft's authorized navigation class. The limit on the data used is determined solely by the existence of such data and the device's ability to consume a data source.

[0111] Step 206 of verifying the existence of conflict allows the type of conflict (air, ground, etc.) to be indicated, the location of the object, and also to provide additional information related to the conflict such as indicating a safety altitude that should be respected in the event of a ground conflict.

[0112] In one embodiment, margins for performing these calculations can 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 (a value for weather conflicts, a 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, low fuel), where a slightly higher risk is permitted but which potentially allows for alternative, and potentially shorter, trajectories (thus allowing the aircraft to land with the remaining fuel). If no conflict is identified, the method informs the flight management system that the calculated 4D trajectory is safe, and that the aircraft can fly it.

[0115] If conflicts are identified, the process continues with an iterative sequence of conflict resolution steps (208), generation by the flight management system of modified intermediate trajectories (210), and trajectory verification 4D modified (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 allows the computer (104), external to the flight management system, to calculate a hierarchical set of solutions with their conflict avoidance parameters, enabling the aircraft to avoid a conflict with at least one identified object. The conflict avoidance parameters are obtained and ranked by implementing conflict resolution algorithm(s).

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

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

[0120] A person skilled in the art understands that [Fig.3] is an example applied to a descent phase, but that the principles described are applicable to various other phases of flight, 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 leveling off during the climb phase can prove effective in avoiding cross traffic. Thus, [Fig. 3] represents a flowchart 300 of a staged conflict resolution step, which appears particularly suited to terrain conflict avoidance, where the method, after determining 302 the existence of a conflict, proceeds with a step 304 to determine if the aircraft is in a descent phase.

[0122] If so, the method makes it possible to check the current altitude of the aircraft, and to determine whether this current altitude is higher or lower than a given safety altitude 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 subsequent 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 subsequent step 308 to call upon 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 allows to request 308 a vertical resolution algorithm.

[0126] After the vertical resolution step 308, the method allows verification 310 of 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 process allows in a subsequent step 312 to request a lateral resolution algorithm.

[0129] An example of conflict resolution hierarchy is shown, which is not limiting, and a person skilled in the art can customize the conflict resolution module according to other configurations.

[0130] An alternative embodiment consists of performing all possible resolutions (lateral, vertical, mixed) and then choosing a posteriori, according to criteria that allow for the direct ranking of the solution trajectories corresponding to said resolutions. In the example of [Fig. 3], the criterion is established upstream (flight phase and aircraft altitude versus conflict altitude). In this case, the criterion is that a vertical avoidance is preferred, except during the descent phase where climbing is prohibited.

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

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

[0133] An n-Dimensional white cane algorithm is based on a principle of angular scanning and step-by-step advancement for each dimension of a trajectory. This type of algorithm resolves a conflict by allowing advancement 'step by step' towards a flight plan to be reached, 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 unbounded, generalized or not in a higher level solver, depending on the computing platform envisaged and the functional constraints that are given (response time, computing resources, complexity / volatility of the trajectory...).

[0136] Returning to [Fig.2], when step 212 of the modified 4D trajectory verification confirms that there is no longer a conflict, the trajectory securing process ends, and the set of avoidance parameters relating to a safe 4D trajectory is provided 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 step 212 of 4D trajectory verification, a message may be raised to inform the aircraft crew.

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

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

[0140] Conflict resolution can be triggered 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 one variant, for performance reasons, the triggering of the process can be limited only to times when the aircraft is at a certain distance from the trajectory, the distance being configurable.

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

[0143] The process 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 including 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 included in the flight plan. These procedures can be defined according to the ARINC 424 standard and may contain altitude constraints associated with navigation points.

[0145] Altitude constraints can be of several types (applicable aeronautical standards determine the tolerances required by aircraft type, navigation airspace class, and possibly other criteria): - constraint “AT”: 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; - constraint “AT or BEL0W”: 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 securing 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 process allows in the next step 404 to check, by the computer external to the FMS, the trajectory with respect to a set of obstacles (terrain, weather, ...) 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 case of conflict(s), the process allows 406 to integrate all the safety altitudes as "pseudo-constraints" in the list of altitude constraints for FMS calculations.

[0150] For example, on a 4D descent trajectory initially calculated by an FMS, A and B are two points with altitude constraints AT. After analyzing and resolving potential conflicts, the safety device calculates a safe position and altitude to avoid a terrain conflict. The method allows the calculated safe position and altitude parameters to be sent back to the FMS to restart the calculation of a 4D trajectory by integrating these avoidance parameters as a "pseudo-altitude constraint AT or ABOVE," or a "virtual altitude constraint" (the altitude not being derived from the published A424 procedure).

[0151] The process 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 risks of conflict or not.

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

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

[0155] In a subsequent step 410, the process allows, via the trajectory securing device, to check the modified 4D trajectory, and to determine 412 whether it is free of any conflict or not.

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

[0157] In one embodiment, in order to warn the crew that the vertical descent profile 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 (ND) 500 screen.

[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... However, there is no "pseudo-waypoint" which is calculated and displayed on a navigation chart, 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 aircraft's position is controlled along a horizontal trajectory and a reference vertical profile. In managed mode, the FMS determines the descent assumptions, the aircraft is controlled along 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 the "selected" mode. The descent assumptions 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 assumptions. However, and advantageously, the method of the invention, which allows the creation of pseudo-constraints, can be applied in selected mode because it informs the pilot about the area and altitude of a conflict. The area where the trajectory is in conflict is then displayed, as well as the pseudo-waypoint indicating the safe altitude that should be adopted.

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

[0163] With this information, the crew can then 'manually' resolve the conflict by adapting their descent instructions. They can also engage 'managed' mode to authorize the FMS to automatically follow the safe descent profile as described above.

[0164] In one embodiment, an alert can be raised when the aircraft is about to descend below a conflict altitude, even well below its current position, given that the system is not designed to allow for climbing during a descent or approach phase to an airport. Thus, once below this altitude, no further vertical correction is possible, and the conflict will occur later (without additional manual corrective action or by switching to a lateral plane resolution, which will inevitably lead to increased flight time and fuel consumption).

[0165] In another embodiment, conflict avoidance can be automated in cases of pilot incapacitation. For example, if no pilot action is taken following an alert message within a certain timeframe, an automatic engagement of 'managed' mode can be activated to empower the FMS to follow the safe descent profile as described above.

[0166] Figure 7 represents a synoptic diagram 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 sequence of calculations that iteratively allow one to rejoin the flight plan initially flown.

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

[0169] In a subsequent step 704, the method makes it possible to calculate a set of rejoin trajectories between the aircraft and the flight plane, based on the headings established in the previous step by the angular scan.

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

[0171] The process ends at 710 by proposing the selected heading instruction to the pilot for engagement of the trajectory.

[0172] The white cane algorithm can be adapted to explore space in a series of lateral maneuvers (i.e., changes of course). The maximum number The maneuvers, and the angular space to be swept for each maneuver, can be configurable (fixed before takeoff; configured by the operator (pilot)). The advantage of this approach is that it limits any proposed solution to a series of actions reasonably computable by a certified onboard system and achievable by an automated system, or executable by a pilot.

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

[0174] In one embodiment, lateral conflict resolution can be based on an "n-Dimensional white cane" type algorithm. This algorithm is based on the same principle of scanning and step-by-step advancement 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 the 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 velocity vector and the local horizon. The execution of a maneuver covers: a lateral angular sweep [heading instruction + / - X°] around a current heading instruction, in steps of "alpha" degrees, and a vertical angular sweep [current FPA + / - X°] around a current FPA angle, in steps of "alpha" degrees. The alpha parameter is calculated from the aircraft's performance, its current situation (altitude, speed, roll), bounded by the flight envelope.

[0176] A subsequent step allows a segment of the trajectory corresponding to each maneuver to be calculated.

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

[0178] Then the algorithm allows the valid maneuver to be selected which has 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 unbounded, generalized or not in a higher-level solver, depending on the computing platform envisaged, and the functional constraints that exist (response time, computing resources, complexity / volatility of the trajectory...).

[0180] In one embodiment, conflict resolution can 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 well-known "A*" algorithm, which is a pathfinding algorithm in a graph between an initial node and a final node, which uses a heuristic evaluation on each node to estimate the best path passing through it, and then visits the nodes in the order of this heuristic evaluation.

[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 stealable, in order to avoid a truly 3D search which is very costly in response time.

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

[0185] The graph traversal conflict resolution algorithm maps the conflict area onto a terrain elevation grid, as illustrated at the bottom of [Fig. 8a]. The terrain elevation grid provides the minimum elevations required to enter each "cell," such as an elevation of 6200 for the cell corresponding to point B, or an elevation of 5800 for the cell corresponding to point A.

[0186] The algorithm then searches for a path constructed backwards from the end of the conflict (i.e., point A) and leading back to the aircraft via the beginning of the conflict (i.e., point B), in order to maintain the aircraft's current flight instructions as closely as possible. This is illustrated in [Fig. 8b], which represents the proposed safe trajectory to avoid the conflict.

[0187] The vertical conflict avoidance profile is shown at the top, starting from the Exit Point at altitude 5800, then going back up, a first point 1 at altitude 6000, a second point 2 at altitude 6300, an Entry Point at altitude 6600, and the aircraft's current position (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 for the fastest possible climb to aircraft altitude, in order to allow the most "cells" possible. Indeed, the faster the ascent, the more cells there will be to choose from when moving from one cell to a neighboring cell.

[0191] According to another embodiment, conflict resolution can be achieved by selecting a speed-based strategy, using parameters such as "time of conflict" provided by the trajectory checker (104). This is particularly applicable if the conflict is mobile or temporary. Advantageously, the calculation and display in the cockpit of a continuous, safe, conflict-free 4D trajectory allows a crew to reduce its workload by offering it a trajectory to follow at any time for landing. The safe trajectory can be sent to the ground to facilitate communication with the aircraft and to anticipate its automatic tracking in case of pilot incapacitation, for example, in a SPO (Single Pilot Operation) environment.

[0192] The method of the invention can be implemented using hardware and / or software components. 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-transient 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 various modules of the system according to the invention can be implemented on the same processor or on the same circuit, or distributed across several processors or 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

Demands

1. Method for calculating a safe 4D trajectory for an aircraft flying on a current 4D trajectory calculated by an aircraft flight management system, comprising the following steps: - calculate (206), by a trajectory checker (106) external to an aircraft flight management system, whether on the current 4D trajectory flown, 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, implement iterative steps until a conflict resolution is reached, allowing a safe trajectory for the aircraft to be defined, the conflict resolution steps consisting of: - generating (208), by a conflict solver (108) external to the flight management system, a list of conflicts identifying conflict avoidance parameters for each type of conflict, and calculating a hierarchical set of solutions with conflict avoidance parameters, said conflict avoidance parameters being obtained by implementing conflict resolution algorithms; - providing the conflict avoidance parameters of a solution to the flight management system to integrate them into a calculation (210) of an intermediate 4D trajectory; - determining (212) by the conflict checker (104), whether on the intermediate 4D trajectory, there is a new risk of conflict for the aircraft;- if there is no risk of conflict, integrate the said conflict avoidance parameters into the flight management system as avoidance maneuvers to be performed to engage the intermediate 4D trajectory as the current safe 4D trajectory for the aircraft; or - if there is a risk of conflict, repeat the previous steps (208) to (212) until a conflict resolution is achieved.

2. A method according to claim 1 wherein the step of determining the risk of conflict by the trajectory checker (106), external to the flight management system, comprises steps of identifying, from different data sources, at least the presence fixed or moving obstacles on the current or modified 4D trajectory, and to check if the obstacle(s) can generate a conflict with the aircraft.

3. A method according to claim 1 or 2 wherein the conflict avoidance parameters are safety altitudes and / or heading values ​​and / or speed values.

4. A method according to any one of the preceding claims wherein the step of calculating a hierarchical set of solutions with conflict avoidance parameters further comprises steps of determining the current flight phase of the aircraft and determining a corresponding conflict resolution procedure.

5. A method according to any one of the preceding claims wherein the step of implementing a conflict resolution procedure consists of implementing one or more conflict resolution algorithms from among vertical resolution, lateral resolution or mixed resolution algorithms.

6. A method according to any one of the preceding claims wherein the step of implementing a conflict resolution algorithm consists of implementing a chain of several conflict resolution algorithms, the chain being predefined or configurable.

7. A method according to any one of the preceding claims wherein the implementation step of a conflict resolution algorithm consists of taking into account one or more intermediate trajectories calculated during the iteration phase.

8. Product computer program comprising code instructions for performing the steps of the method for calculating a safe 4D aircraft trajectory according to any one of method claims 1 to 7, when said program is executed on a computer.

9. Device for calculating a safe 4D aircraft trajectory, the device comprising means configured to implement the steps of any one of claims 1 to 7 of the method for calculating a safe 4D aircraft trajectory.

10. Aircraft flight management system comprising means for operating with a safe 4D aircraft trajectory calculation device according to the preceding claim.

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

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