Improved method for calculating a flight trajectory for an aircraft; Navigation system, aircraft and associated computer program product.
A nested loop method in aircraft navigation systems iteratively updates flight trajectories, combining safety and optimality to provide efficient, adaptable, and safe flight paths, addressing the limitations of existing systems.
Patent Information
- Application Number
- FR2023015460
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-12-29
- Publication Date
- 2026-01-16
- Estimated Expiration
- 2043-12-29
AI Technical Summary
Existing navigation systems for aircraft fail to provide optimal and dynamically adaptable flight paths due to limited computing resources and infrequent updates, leading to suboptimal and unsafe flight trajectories.
A method involving a nested loop structure with short/medium and long-term calculations to iteratively update flight trajectories, ensuring safety and optimality by combining long-term safety constraints with short-term operational adaptability, using a navigation system with modules for constraint consolidation, calculation, and validation.
The method provides a safe and optimized flight path that adapts to operational conditions, reducing computational workload and ensuring rapid response to changes, enhancing aircraft guidance and navigation efficiency.
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Abstract
Description
Title of the invention: Improved method for calculating a flight trajectory for an aircraft; Navigation system, aircraft and associated computer program product.
[0001] The invention relates to the field of navigation systems for an aircraft and methods, implemented by such a navigation system, for calculating a flight trajectory of the aircraft.
[0002] Document FR 3 131 956 presents a method for calculating a flight trajectory implemented by the computer of an aircraft navigation system.
[0003] This method is executed periodically using, for example, a mission description flight plan, the current position of the aircraft, and current operating conditions.
[0004] Initially, a set of trajectories is calculated by uncertified algorithms. This set of trajectories includes a nominal trajectory and several diversion trajectories.
[0005] The nominal trajectory is calculated from, for example, an aircraft flight plan and enables the aircraft to carry out the mission assigned to it, such as reaching a destination airport.
[0006] Each diversion trajectory is calculated so as to respond to one or more particular hazard(s) occurring during the flight of the aircraft, while the latter is guided along the nominal trajectory.
[0007] In a second step, the set of calculated trajectories is validated for safety by a certified algorithm.
[0008] Finally, in a third step, at each instant of the flight, one trajectory from this set of trajectories is selected as the flight path and is transmitted, as an instruction, to an aircraft guidance system. When an unforeseen event occurs, the corresponding diversion trajectory is selected as the new flight path, allowing the aircraft to deviate from the nominal trajectory and land on the nearest runway.
[0009] The flight trajectory followed therefore ensures the safety of the flight from beginning to end.
[0010] The navigation system architecture presented in this prior art document is interesting because it allows the generation of trajectories, including diversion trajectories, by uncertified algorithms, and then their validation by a certified algorithm.
[0011] This goes against the architecture of classic navigation systems – FMS (“Flight Management System”), in which a calculation algorithm for the A flight path calculation based on flight plan information is performed regularly during the aircraft's flight to calculate a single nominal trajectory. To ensure the validity of this calculated flight path, the algorithm itself must be certified beforehand. Furthermore, this algorithm must be run on a certified computer (or critical computer).
[0012] It is therefore understandable that the principle set out in document FR 3 131 956 is particularly promising.
[0013] However, even if the flight path followed by the aircraft guidance system meets end-to-end safety criteria, this flight path is not always optimal. Indeed, the trajectories of all the flight paths, particularly the nominal trajectory, may be suboptimal if they are not updated in real time according to the current flight conditions.
[0014] Furthermore, the adaptability of this flight path to operational constraints remains limited. Indeed, calculating the entire set of trajectories is costly in terms of computing resources and processing time. However, the processing power of onboard aircraft computers, especially drones, is severely limited and does not allow for very frequent updates of these trajectories.
[0015] The invention therefore aims to improve the navigation system according to the state of the art.
[0016] For this purpose, the invention relates to a method for calculating a flight trajectory for an aircraft, characterized in that the method comprises a short / medium term loop, the steps of which are iterated at a high frequency, nested within a long term loop, the steps of which are iterated at a low frequency, the long term loop leading to the calculation of a long term trajectory, the long term trajectory being calculated to meet safety criteria, and the short / medium term loop leading first to the calculation of a short term trajectory, then to the calculation of a medium term trajectory, the short term trajectory being calculated to meet optimality criteria, the medium term trajectory joining the short term trajectory with the long term trajectory.
[0017] According to particular embodiments, the process comprises one or more of the following characteristics, taken individually or in all technically possible combinations:
[0018] - the long-term loop comprises the steps of: consolidation of a plurality of safety constraints; calculation, based on the plurality of safety constraints, a current aircraft position, a plurality of characteristic aircraft technical capabilities, and a mission assigned to the aircraft, of a set of long-term trajectories at the current time, said set comprising a nominal trajectory and a plurality of diversion trajectories; and, Selection, as a tra long-term trajectory at the current time, in the set of long-term trajectories at the current time, of the nominal trajectory or one of the diversion trajectories.
[0019] - the short / medium term loop comprises the steps of: consolidation of a plurality of operational constraints and a plurality of safety constraints; calculation, based on the plurality of operational constraints, the plurality of safety constraints, a current position of the aircraft and a mission, of a short-term trajectory at the current time; calculation, based on the plurality of safety constraints, the short-term trajectory and the long-term trajectory, of a medium-term trajectory.
[0020] - at each time step, the long, medium and short term trajectories are aggregated in a flight trajectory, the flight trajectory being transmitted to an aircraft guidance system.
[0021] - once the long, medium and short term trajectories are aggregated into a trajectory of In flight, the flight trajectory is validated according to safety criteria before being transmitted to the aircraft guidance system.
[0022] - with a time step equal to one second, the short / medium term loop is iterated with a period of one second, and the long-term loop is executed with a period of 60 seconds.
[0023] - the mission is a flight plan.
[0024] The invention also relates to a navigation system intended to be carried on board an aircraft, characterized in that it is adapted to implement the method of calculating a previous flight trajectory.
[0025] The invention also relates to an aircraft carrying a navigation system conforming to the previous navigation system.
[0026] The invention also relates to a computer program product comprising software instructions which, when executed by an aircraft on-board computer, implement a navigation method in accordance with the previous method.
[0027] The invention and its advantages will be better understood upon reading the following detailed description of a particular embodiment, given solely by way of illustration and not limitation, this description being made with reference to the accompanying drawings in which: - [Fig.1] The [Fig.1] is a schematic representation, in the form of functional modules, of the navigation system according to the invention; - [Fig.2] Fig.2 is a block representation of the process of trajectory calculation implemented by the navigation system of [Fig. 1]; and, - [Fig. 3] [Fig. 3] is a representation of the temporal evolution of the tra flight path calculated by the navigation system of [Fig. 1].
[0028] In general, the method according to the invention consists of combining long-term navigation, allowing the safety of the flight until landing, and short-term navigation, allowing optimal execution of the mission.
[0029] In accordance with the prior art, long-term navigation relies on a set of trajectories, from which the safe trajectory is selected. However, these trajectories are neither optimal nor particularly dynamically adaptable.
[0030] Short-term navigation meets the criteria of optimality and high adaptability, since the short-term trajectory is constructed as the flight progresses. However, this short-term trajectory alone does not guarantee flight safety, as it does not cover the entire flight up to landing.
[0031] Finally, according to the invention, a medium-term trajectory is calculated allowing the short-term and long-term trajectories calculated separately to be linked.
[0032] The flight trajectory then results from the concatenation of the short, medium and long term trajectories.
[0033] The flight trajectory is advantageously validated for its safety before being transmitted to the aircraft guidance system.
[0034] In what follows, the qualifiers short, medium and long term are to be seen more in terms of a distance scale, rather than a time scale, although these two scales are correlated through the aircraft speed parameter.
[0035] Operational constraints are those related to the mission (mission objective, performance criteria, etc.). Safety constraints are those related to flight safety (obstacles, no-fly zones for safety reasons, aircraft performance requirements to avoid a crash).
[0036] Fig. 1 represents a preferred embodiment of a navigation system according to the invention, intended to be carried on board an aircraft.
[0037] The navigation system 10 is adapted to periodically calculate a flight path and transmit it to an aircraft guidance system 20 as an instruction to steer the aircraft along that path. Usually, the guidance system is actually integrated into the navigation system.
[0038] The navigation system 10 is a computer comprising computing means, such as a processor, and storage means, such as memory. The memory stores, in particular, the instructions of computer programs, specifically a program whose execution enables the implementation of the method for calculating a flight trajectory according to the invention.
[0039] The execution of this program enables the navigation system 10 to be equipped with a plurality of functionalities, schematically represented in the form of modules functional on the [Fig.l].
[0040] The navigation system 10 thus includes a module 15 for updating the safety constraints at the current time CS(t). This module takes as input, in particular, the technical capabilities of the aircraft as planned by its designer (such as range, power, glide ratio, etc.), meteorological information provided by the local meteorological organization, and the airspace and altitudes authorized for the flight in order to guarantee its safety, provided by the aeronautical information services.
[0041] The navigation system 10 includes a long-term trajectory calculation module, 12. In accordance with the prior art, the module 12 takes as input, for example, the mission M to be carried out, which may take, for example, the form of a flight plan, the current position P(t) of the aircraft, the aircraft's characteristic heading capabilities, and the safety constraints at the current time CS(t). The module 12 outputs a set of trajectories at the current time t. This set is denoted E(t).
[0042] The set E(t) comprises a nominal trajectory Tn(t) and a plurality of diversion trajectories Td(t), whose starting points are located along the nominal trajectory Tn(t). In both cases, these are long-term trajectories.
[0043] Advantageously, the navigation system 10 also includes a validation module 8, in accordance with the prior art, allowing validation of the safety of the set of trajectories E(t).
[0044] The navigation system 10 includes a database 11 allowing the recording of the set of trajectories at the current time E(t) validated by the module 8.
[0045] The navigation system 10 includes a selection module 13 allowing selection, in the database 11, of a long-term trajectory at the current time TL(t) from among the set of trajectories E(t).
[0046] The navigation system 10 includes a module 17 for updating operational constraints at the current time COp(t). This module takes as input, in particular, the mission objectives specified by the aircraft operator and any geographical (authorized airspace, terrain, obstacles) and technical (payload performance) constraints affecting the success of the mission.
[0047] The navigation system 10 includes a short-term trajectory calculation module 14. The module 14 takes as input, for example, the operational conditions at the current time Cop(t), the mission M, the aircraft's characteristic heading capabilities, the safety constraints at the current time CS(t), and the aircraft's position P(t) at the current time. The module 14 outputs a short-term trajectory at the current time, TC(t).
[0048] The navigation system 10 includes a medium-term trajectory calculation module, 16. The module 16 takes as input the short-term trajectory at the current time, TC(t) output from module 14, the long-term trajectory at the current time, TL(t) output from module 13 (essentially the starting point of the selected nominal long-term trajectory Tn(t), the aircraft's characteristic heading capabilities, and, preferably, the safety constraints at the current time, CS(t) output from module 15. Module 16 outputs a medium-term trajectory at the current time, TM(t).
[0049] The medium-term trajectory connects the short-term and long-term trajectories. This connection must ensure continuity in the aircraft's position and velocity. Flight constraints are taken into account to establish each connection.
[0050] The navigation system 10 includes an aggregation module 18 which, from the short-term trajectories at the current time, TC(t), medium-term trajectories at the current time, TM(t), and long-term trajectories at the current time, TL(t), calculates a single object or flight trajectory at the current time T'(t).
[0051] Advantageously, the navigation system 10 also includes a validation module 19, in accordance with the prior art, allowing the safety of the flight trajectory T'(t) to be validated before it is transmitted, as a flight trajectory T(t), to the guidance module 20. The validation module 19 may take into account the validation of the entire trajectory E(t) possibly carried out previously by the validation module 8.
[0052] The trajectory calculation modules 12, 14, and 16 each execute an algorithm known to those skilled in the art to calculate the long-term, short-term, and medium-term trajectories, respectively. For example, the following may be implemented: - algorithms of the same type as those of a state-of-the-art FMS, if the aircraft has to follow aeronautical procedures (particularly for long-term trajectories); - Classic trajectory and / or path calculation algorithms for missions such as surveillance, tracking, rescue, etc.; - algorithms based on machine learning.
[0053] Fig. 2 represents a preferred embodiment of the flight trajectory calculation method according to the invention.
[0054] The method 100 is implemented by the navigation system 10 of the [Fig. 1], during the flight of aircraft 1.
[0055] The process 100 includes a short / medium term loop 120 nested within a long term loop 110. These two loops are in fact executed in parallel, the calculations of the long term loop allowing a set of trajectories to be obtained taking more time.
[0056] For example, the short / medium term loop 120 is iterated every 1 second, while the long term loop is iterated every 60 seconds.
[0057] An iteration of the long ternate loop 110 will now be presented.
[0058] In a step 111 of loop 110, safety constraints are consolidated at the current time. Step 111 consists of executing module 15. This includes, for example, constraints related to: - to the terrain (the safe altitude); - to the weather (winds and dangerous weather phenomena); - to regulations (authorized or prohibited geographical areas, procedures to be respected); - to runways (closure of an airport for example); - to the aircraft (range and performance).
[0059] At the output of step 111, a safety constraint vector at the current time, CS(t), is provided. This vector includes, within the mission area, the prohibited and authorized zones, the procedures to be followed and the available landing strips as well as the aircraft performance parameters.
[0060] Then, in step 112, a set of long-term trajectories is calculated and then validated. This step consists of executing modules 12 and then 8.
[0061] This step aims to update all long-term trajectories at the current time E(t) stored in database 11.
[0062] For step 112, for example, not only the current position P(t) of aircraft 1, the mission M to be carried out, the capabilities Cap of the aircraft, but also the safety constraint vector CS(t) are considered.
[0063] A nominal trajectory at the current time Tn(t) is calculated between the current position P(t) of the aircraft and the position of the end of mission indicated by the mission M (landing runway of the destination point for example).
[0064] Different diversion (or contingency) trajectories are calculated at the current time Td(t). Each trajectory Td(t) is associated with one or more hazards to which it responds. Each trajectory Td(t) departs from the nominal trajectory at the current time Tn(t) towards alternative landing strips located near the nominal trajectory.
[0065] A diversion trajectory is calculated so that, if a hazard occurs along the nominal trajectory, the aircraft leaves the nominal trajectory and follows the diversion trajectory in order to bring the aircraft back safely to the ground taking into account the hazard.
[0066] The different trajectories of the set E(t) are potential long-term trajectories which may be suboptimal. They take into account conservative performance parameters of the aircraft (low rate of climb and large turning radius for example) allowing the aircraft to fly the calculated trajectory even in unfavorable conditions: engine failure, failure of certain control surfaces, strong wind, etc.
[0067] At the output of step 112, the set of trajectories at the current time E(t) calculated is validated from a security point of view by the validation module 8, then stored in database 11 for use during the iterations of the short / medium term loop 120. The content of database 11 will be updated during the next iteration of the long term loop 110.
[0068] The short / medium term loop 120 comprises the following steps:
[0069] Step 121 allows testing a condition on the state of the aircraft. Step 121 corresponds to the execution of module 13.
[0070] Depending on the current state S(t) of the aircraft, either the nominal trajectory or one of the diversion trajectories is selected from database 11. The selected trajectory becomes the long-term trajectory at the current time, TL(t).
[0071] The other steps of the short / medium term loop 120 are implemented only in nominal aircraft operation, i.e. when the nominal trajectory has been selected as the long term trajectory at the current time TL(t).
[0072] The short / medium term loop continues with step 122.
[0073] Step 122 consists of consolidating the current operational constraints. Module 17 is executed for the current time step.
[0074] For example, the aircraft's mission objective M is updated at the current time step. This is the case, for example, when the mission objective is to track a target; then the position and velocity of that target (delivered, for example, by a radar system on board the aircraft) are updated during step 122.
[0075] At the output of step 122, the operational constraint vector at the current time COp(t) is obtained.
[0076] Step 124 consists of calculating a short-term trajectory at the current time, TC(t).
[0077] To do this, module 14 is executed.
[0078] This step takes as input, for example, the current position of the aircraft P(t), the mission M to be carried out, the characteristic Cap capabilities of the aircraft, the operational constraint vector COp(t), and the safety constraints at the current time CS(t).
[0079] Advantageously, the short-term trajectory calculation is such that it leads to an optimal trajectory, taking into account the aircraft's nominal capabilities. For example, if the objective is to climb to a certain altitude, the short-term trajectory allows the aircraft to reach this objective with a climb at the aircraft's optimal gradient.
[0080] In step 126, a medium-term trajectory at the current time, TM(t), is calculated.
[0081] This should allow the short-term trajectory TC(t) calculated at the output of step 124 to be joined with the long-term trajectory TL(t) at the output of step 121.
[0082] Step 126 consists of executing module 16.
[0083] One condition for calculating the medium-term trajectory is, for example, to minimize the distance between the endpoint of the short-term trajectory TC(t) and the point of departure from the long-term trajectory TL(t), while respecting criteria for joining these two trajectories. These criteria are based on the nominal capabilities Head of aircraft 1, for example on a minimum radius of curvature of the aircraft, a continuous speed at the point of junction, etc.
[0084] Preferably the safety constraints at the current time CS(t) are also taken into account in step 126.
[0085] Step 128 then consists of combining the short, medium, and long-term trajectories at the current time into a single flight trajectory usable by the aircraft's guidance system 20. For this purpose, the aggregation module 18 is executed. A trajectory T'(t) is thus obtained from TL(t), TM(t), and TC(t).
[0086] Optionally, in step 129, the safety of the flight trajectory T'(t) at the exit of module 18 is verified. This step corresponds to the execution of module 19.
[0087] This allows verification a posteriori, i.e. once the flight trajectory has been calculated, that it is safe from beginning to end.
[0088] Once validated, the flight trajectory at the current time T(t) is transmitted to the guidance module 20. In the event of invalidation of the new calculated trajectory, the update of the trajectory is not continued, and the last validated trajectory is retained.
[0089] Thus, updating the short-term trajectory while retaining the nominal trajectory as the long-term trajectory makes it possible to construct a flight path for the aircraft that is highly responsive to changes in operational constraints Cop(t), particularly the occurrence of unexpected events. Compared to the prior art, where changes in operational constraints are only taken into account through the calculation of a new set of long-term trajectories, the invention allows for a much shorter reaction time.
[0090] Moreover, since the short-term trajectory is optimal, the trajectory actually followed at each instant by the aircraft becomes optimal.
[0091] Figure 3 illustrates the implementation of the invention. An aircraft A carries the device 10 and implements the method 100. Figure 3 illustrates the flight path followed by aircraft A over a period of 60 s.
[0092] At time t=0, the long loop 110 completes a first iteration allowing the calculation of the set of long-term trajectories E(0). It includes a nominal trajectory Tn(0) and several diversion trajectories Td(0).
[0093] During the next 60 iterations of the short / medium term loop 120, between t=0 and t=59, the long term trajectory will be selected from this set E(0). Barring randomness, the long term trajectory is therefore equal to Tn(0).
[0094] The iteration of the short / medium term loop 120 at t=0 allows to calculate a short term trajectory TC(0), then a medium term trajectory TM(0) connecting TC(0) and Tn(0).
[0095] The iteration of the short / medium term loop 120 at t=l allows to calculate a short term trajectory TC(1), then a medium term trajectory TM(1) connecting TC(1) and Tn(0).
[0096] Iterating the short / medium term loop 120 at t=2 allows us to calculate a short term trajectory TC(2), then a medium term trajectory TM(2) connecting TC(2) and Tn(0)...
[0097] The iteration of the short / medium term loop 120 at t=59 allows to calculate a short term trajectory TC(59), then a medium term trajectory TM(59) connecting TC(59) and Tn(0).
[0098] At t=60, the long term loop 110 completes a second iteration allowing the calculation of a new set of long term trajectories E(60), which includes the long term trajectories (Tn(60) or Td(60)) which will be used during the next 60 iterations of the short / medium term loop 120.
[0099] The iteration of the short / medium term loop 120 at t=60 allows to calculate a short term trajectory TC(60), then a medium term trajectory TM(60) connecting TC(60) and Tn(60).
[0100] The trajectory Tf actually followed by aircraft 1 is finally the association of the portions of the short-term trajectories TC(t) actually traveled by the aircraft between two iterations of the loop 110. This trajectory is therefore optimal, at least in portions.
[0101] The present invention has many advantages.
[0102] In particular, the short-term trajectory allows for increased efficiency while the long-term trajectory is conservative.
[0103] Decoupling calculations between short-term, medium-term and long-term trajectories allows for parallelization of calculations, and thus reduces the workload on the on-board computer.
[0104] Furthermore, the performance constraints on the computer are also eased thanks to the long time loop which makes it possible to reduce the frequency at which the set of long-term trajectories is updated, which, in the calculation of the flight trajectory, is the part requiring the most computing resources.
[0105] Thus, the navigation function according to the invention provides the aircraft with a safe, optimized flight path adapted to operational conditions, on which the aircraft can guide itself.
[0106] The invention is applicable to any navigation function, in particular for autonomous aircraft, primarily drones.
[0107] It applies to air transport (passengers or freight), in particular for autonomous aircraft (drones and unmanned aircraft).
[0108] When the process is implemented in the form of one or more software programs, i.e. In the form of a computer program, also called a computer program product, it is further capable of being stored on a computer-readable medium, not shown here. A computer-readable medium is, for example, a medium capable of storing electronic instructions and being connected to a bus of a computer system. Examples of such a readable medium include an optical disc, a magneto-optical disc, ROM, RAM, any type of non-volatile memory (e.g., FLASH or NVRAM), or a magnetic card. A computer program, comprising software instructions, is then stored on this readable medium.
Claims
Demands
1. A method (100) for calculating a flight trajectory (T(t)) for an aircraft (A), characterized in that the method comprises a short / medium term loop (120), whose steps are iterated at a high frequency, nested within a long term loop (110), whose steps are iterated at a low frequency, the long term loop (110) leading to the calculation of a long term trajectory (TL(t)), the long term trajectory being calculated to meet safety criteria, and the short / medium term loop (120) leading first to the calculation of a short term trajectory (TC(t)), then to the calculation of a medium term trajectory (TM(t)), the short term trajectory being calculated to meet optimality criteria, the medium term trajectory joining the short term trajectory with the long term trajectory.
2. A method according to claim 1, wherein the long-term loop (110) comprises the steps of: - consolidation (111) of a plurality of safety constraints; - calculation (112), as a function of the plurality of safety constraints, a current position of the aircraft, a plurality of technical capabilities characteristic of the aircraft, and a mission assigned to the aircraft, of a set of long-term trajectories at the current time (E(t)), said set E(t) comprising a nominal trajectory (Tn(t)) and a plurality of diversion trajectories (Td(t)); and, - Selection (121), as a long-term trajectory at the current time (TL(t)), from the set of long-term trajectories at the current time (E(t)), of the nominal trajectory or one of the diversion trajectories.
3. A method according to claim 1 or claim 2, wherein the short / medium term loop (120) comprises the steps of: - consolidation (122) of a plurality of operational constraints and a plurality of safety constraints; - calculation (124), as a function of the plurality of operational constraints, the plurality of safety constraints, a current aircraft position and a mission, of a short term trajectory at the current time (TC(t)); - calculation (126), based on the plurality of security constraints, the short-term trajectory and the long-term trajectory, of a medium-term trajectory.
4. A method according to any one of the preceding claims, wherein, at each time step, the long, medium and short term trajectories are aggregated (128) into a flight trajectory, the flight trajectory being transmitted to a guidance system (20) of the aircraft.
5. A method according to claim 4, wherein, once the long, medium and short term trajectories have been aggregated into a flight trajectory, the flight trajectory is validated (129) according to safety criteria before being transmitted to the aircraft guidance system.
6. A method according to any one of the preceding claims, wherein, with a time step of one second, the short / medium term loop (120) is iterated with a period of one second, and the long term loop (110) is executed with a period of 60 seconds.
7. A method according to any one of the preceding claims, wherein the mission is a flight plan.
8. Navigation system (10) intended to be carried on board an aircraft (A), characterized in that it is adapted to implement a method for calculating a flight trajectory according to any one of claims 1 to 7.
9. Aircraft (A) carrying a navigation system (10), characterized in that the navigation system conforms to the navigation system of claim 8.
10. Product computer program comprising software instructions which, when executed by an aircraft on-board computer, implement a navigation method in accordance with the method according to any one of claims 1 to 7.