System for managing emergency landing trajectory of drone or unmanned aerial vehicle

Abstract

A system for managing emergency landing trajectories of a drone (1), comprising:-a ground control station (2) comprising a first computer (3) equipped with: a determination module (4) for continuously determining a first emergency landing trajectory; and an inspection module (5) for inspecting the first trajectory; and-a control unit (6) on the drone, the control unit (6) comprising a second computer (7), the second computer (7) comprising: a determination module (8) for continuously determining a second landing trajectory; a detection module (9) for detecting a severe hazard involving a switching from a nominal mode to an emergency landing mode, the emergency landing mode activating operation of the selection module to select a first emergency landing trajectory or a second emergency landing trajectory; a selection module (10) configured to select either a first designed emergency landing trajectory or a second emergency landing trajectory in such a way that the first trajectory is selected if the first trajectory takes into account a current value of an operational or environmental parameter of the drone representative of the detected severe hazard, and the second trajectory takes into account a current value of an operational or environmental parameter of the drone representative of the detected severe hazard; and selecting a second trajectory if the first trajectory takes into account a last received value different from a current value of an operational or environmental parameter of the drone representing the detected severe hazard.

Description

Technical Field

[0001] The present invention relates to a system for managing an emergency landing trajectory of a drone or an unmanned aerial vehicle.

[0002] The present invention relates to an unmanned aerial vehicle or a drone. The present invention relates to determining an emergency landing solution in a situation of severe danger that requires a quick landing in an area where there is no risk of human loss. The danger can be caused by weather, a malfunction of the on-board system, or a loss of positioning.

[0003] The object of the present invention is to solve the problem of taking a decision to interrupt a mission far from the operator without a proper reconstruction of the environment, especially in the case of a delay in the transmission of information from the drone due to its remoteness or even a transmission loss. Background Art

[0004] So far, the operator of an unmanned aerial vehicle or a drone has been responsible for detecting a danger that no longer allows the mission to continue. Depending on his perception of the severe danger, his role consists of using simple macro commands such as "return to base" or "land the drone in place", for example by spiraling down to the ground.

[0005] These solutions work well when the drone moves at a short distance from the operator and the operator has good knowledge of the environment of the drone. This is not the case when the mission lasts for several hours. Then the system must provide an automatic solution for the operator.

[0006] Long-range drone operations, or in other words, flight missions over 10 km, must provide solutions for various severe dangers, such as:

[0007] - A critical level of energy autonomy: energy monitoring detects that the drone no longer has the capacity to reach the nearest predefined landing area;

[0008] - A decrease in flight performance due to actuator failures, excessive wind, or structural problems due to a collision with an external element, where tracking the position of the drone relative to the trajectory detects that the guidance and autopilot functions no longer allow following the trajectory; or - A critical deviation of the position in the case of a GNSS position loss, where tracking is carried out and, over a certain period of time, the increase in uncertainty no longer ensures the airworthiness of the drone.

[0009] In these cases, an emergency mode is defined so that the drone responds to the severe danger.

[0010] In the case of remote operation, traditional flight termination systems (FTS) (which include triggering the opening of a parachute or performing a spiral descent) are not feasible because it is difficult for the operator to accurately understand the situation as the drone is dozens or even hundreds of kilometers away from the operator.

[0011] Existing solutions for finding a path between two points while avoiding obstacles use pathfinding algorithms. However, in the case of drones, low-cost airborne hardware solutions cannot provide the necessary performance for such algorithms.

[0012] In addition, due to competitiveness reasons, the development cost of drones must be minimized. Due to the development cost related to certification and performance levels, pathfinding solutions cannot be selected. Summary of the Invention

[0013] An object of the present invention is to respond to the above problems and focus on an emergency landing trajectory calculated by a drone system (ground / airborne) in a serious dangerous situation where the aircraft needs to land as quickly as possible. The trajectory must bring the aircraft to an area without human activities while ensuring the observation of no-fly zones, taking into account the terrain and the presence of obstacles such as prohibited areas.

[0014] According to an aspect of the present invention, a system for managing an emergency landing trajectory of a drone is proposed, including:

[0015] - A ground control station, including a first computer equipped with:

[0016] - A determination module for continuously determining a first emergency landing trajectory considering the last value of at least one parameter representing the operation or environment of the drone and an emergency landing database, the value being received from the drone, the determination module being configured to calculate the first emergency landing trajectory according to a path search algorithm, the emergency landing database, and the last received value of the operation or environment parameters of the drone; and

[0017] - A verification module for verifying the first trajectory according to the emergency landing database; and

[0018] - The on-board control unit of the drone, including a second computer, the second computer including:

[0019] - A determination module configured to continuously determine a second emergency landing trajectory based on the emergency landing database and current values of at least one operational or environmental parameter of the drone. The determination module is configured to calculate the second emergency landing trajectory by including lateral trajectory calculation and vertical trajectory calculation for each emergency landing point, and the determination module is configured to check that the emergency trajectory is fixed within a safety corridor based on the emergency landing database and the last values of the operational or environmental parameters of the drone;

[0020] - A detection module configured to detect a critical hazard related to a switch to an emergency landing mode, a hazard that has been detected based on current values of at least one operational or environmental parameter of the drone. The emergency landing mode activates the function of a selection module for selecting the first emergency landing trajectory or the second emergency landing trajectory; and

[0021] - A selection module configured to select the first designed emergency landing trajectory or the second emergency landing trajectory in the following manner: if the first trajectory takes into account the current values of the operational or environmental parameters of the drone representing the detected critical hazard, then select the first trajectory, and if the first trajectory takes into account the last received values that are different from the current values of the operational or environmental parameters of the drone representing the detected critical hazard, then select the second trajectory.

[0022] In one embodiment, the landing database includes polygonal landing areas, no - fly zones, and obstacles.

[0023] According to one embodiment, the landing database includes landing points with associated final approach axes and associated altitudes, no - fly zones, and obstacles.

[0024] In one embodiment, the determination module for continuously determining the second emergency landing trajectory is configured to calculate emergency landing points by: defining a landing point search area; identifying sections of polygons that are directly visible in a straight line; and for each landing point, performing the following operations:

[0025] - Determining the final approach axis for each landing point; and

[0026] - Checking compliance of the trajectory with a safety corridor that avoids no - fly zones and obstacles.

[0027] According to one embodiment, the determination module for continuously determining the second emergency landing trajectory is configured to evaluate the landing points in order from closest to farthest by calculating a lateral trajectory, an emergency landing vertical trajectory, and an associated safety corridor.

[0028] In one embodiment, the second computer has less computing power than the first computer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The present invention will be better understood by studying some embodiments described as non - limiting examples and illustrated by the accompanying drawings, in which:

[0030] Figure 1 schematically shows a system for managing an emergency landing trajectory of an unmanned aerial vehicle according to one aspect of the present invention; and

[0031] Figure 2 schematically shows an emergency landing database according to one aspect of the present invention;

[0032] Figure 3 schematically shows the on - board identification of an unmanned aerial vehicle in a landing area of a database of an emergency landing database according to one aspect of the present invention;

[0033] Figure 4 schematically shows the on - board assessment of an unmanned aerial vehicle of eligible landing points along a lateral trajectory; and

[0034] Figure 5 schematically shows the on - board assessment of an unmanned aerial vehicle of the change of eligible landing points along a vertical trajectory according to one aspect of the present invention.

[0035] In all the drawings, elements having the same reference numerals are similar. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] Figure 1 schematically shows a system for managing an emergency landing trajectory of an unmanned aerial vehicle 1 according to one aspect of the present invention. The system includes a ground control station 2, and the ground control station 2 includes a first computer 3, and the first computer 3 is equipped with the following:

[0037] - A determination module 4 for continuously determining a first emergency landing trajectory in consideration of the last value of at least one parameter representing the operation or environment of the unmanned aerial vehicle and an emergency landing database, the value being received from the unmanned aerial vehicle; and

[0038] - An inspection module 5 for inspecting the first trajectory according to the emergency landing database.

[0039] ​​​​​​The sensors 14 of the drone 1 provide measurements to the transceiver module 11 of the drone 1, and the transceiver module 11 sends them to the first computer 3 of the ground control station 2. The sensors 14 of the drone 1 also provide these measurements to the flight tracking module 12, which tracks the flight of the drone 1 and allows determination of hazards based on these measurements of the sensors 14, such as inability to fly to the end of the mission with the remaining energy capacity, excessive lateral and vertical deviations of the trajectory compared to predefined thresholds, or equipment failures.

[0040] The system also includes an on-board control unit 6 on the drone, and the control unit 6 includes a second computer 7, which has, for example, lower computing power compared to the first computer 3. The second computer 7 includes:

[0041] - A determination module 8 for continuously determining a second emergency landing trajectory based on an emergency landing database and current values of at least one operation or environmental parameter of the drone;

[0042] - A detection module 9 for detecting a severe hazard, which involves switching to the emergency landing mode and detecting a hazard based on current values of at least one operation or environmental parameter of the drone, and activating the operation of the emergency landing mode selection module 10 to select a first emergency landing trajectory or a second emergency landing trajectory; and

[0043] - A selection module 10 configured to select a first designed emergency landing trajectory or a second emergency landing trajectory in the following manner: if the first trajectory takes into account the current values of the operation or environmental parameters of the drone representing the detected severe hazard, then select the first trajectory, and if the first trajectory takes into account the last received values different from the current values of the operation or environmental parameters of the drone representing the detected severe hazard, then select the second trajectory.

[0044] The determination module 4 for continuously determining the first emergency landing trajectory is configured to calculate the first emergency landing trajectory based on a path search algorithm, an emergency landing database, and the last received values of the operation or environmental parameters of the drone.

[0045] The determination module 8 for continuously determining the second emergency landing trajectory is configured to calculate the second emergency landing trajectory by including a lateral trajectory calculation and a vertical trajectory calculation for each emergency landing point, and the determination module 8 is configured to check that the emergency trajectory is fixed within a safety corridor based on the emergency landing database and the last values of the operation or environmental parameters of the drone.

[0046] The landing database includes a polygonal landing zone LZ and a no-fly zone NFZ.

[0047] The landing database includes landing points and no-fly zones with associated final approach axes and associated altitudes.

[0048] The determination module 8 for continuously determining the second emergency landing trajectory is configured to calculate an emergency landing point by: defining a landing point search area; and for each landing point, performing the following operations:

[0049] - Identifying the sections of the polygon that are directly visible in a straight line;

[0050] - Determining the final approach axis for each landing point; and

[0051] - Checking compliance with the safety corridor of the trajectory for avoiding no - fly zones.

[0052] The determination module 8 for continuously determining the second emergency landing trajectory is configured to evaluate the landing points in order from the nearest to the farthest by calculating an emergency landing lateral trajectory and a vertical trajectory.

[0053] The basic idea of the present invention is to use two separate emergency trajectory calculation algorithms on two computers: performing simple trajectory calculations on the unmanned aerial vehicle and performing a more refined solution on the ground control station.

[0054] The on - board trajectory selection algorithm allows the system to switch to the emergency mode to select the emergency trajectory to fly. The selected trajectory is then sent to the guidance / control module 13 for execution.

[0055] The determination module 8 of the second computer 7 on board calculates the second basic "direct - to" trajectory between the unmanned aerial vehicle and the landing area. In the ground control station 2, the determination module 4 of the first computer 3 calculates the second more complex trajectory and then returns it to the unmanned aerial vehicle.

[0056] The selection module 10 is configured to select the first designed emergency landing trajectory or the second emergency landing trajectory in the following manner: if the first trajectory takes into account the current values of the operating or environmental parameters of the unmanned aerial vehicle representing the detected serious hazard, then select the first trajectory, and if the first trajectory takes into account the last received values different from the current values of the operating or environmental parameters of the unmanned aerial vehicle representing the detected serious hazard, then select the second trajectory.

[0057] The flight tracking module 12 of the unmanned aerial vehicle 1 detects that it cannot fly to the end of the mission with the remaining energy capacity, that the lateral and vertical deviations are too large compared to the predefined thresholds, and equipment failures. The result of this tracking is sent to the serious hazard detection module 9. In the case where a serious hazard is detected that no longer allows the mission to continue and an emergency landing is required (e.g., within two or three minutes), the serious hazard detection module 9 switches to the emergency landing mode. The ground operator also has the ability to trigger an emergency landing if he deems the current situation requires it.

[0058] The present invention achieves:

[0059] - Provide a reasonable computational load in the UAV using low-capacity hardware;

[0060] - Reasonable authentication cost;

[0061] - Perform algorithmic simulations on the ground during mission preparation to verify the landing solution throughout the mission; and

[0062] - Eliminate the need to store a set of emergency solutions calculated on the ground on the UAV to respond to severe hazards in case of loss of communication.

[0063] When an emergency hazard involving a switch to the emergency landing mode is detected, the selection module 10 selects the first designed emergency landing trajectory or the second emergency landing trajectory in the following manner: If the first trajectory takes into account the current values of the operating or environmental parameters of the UAV representing the detected severe hazard, the first trajectory is selected, and if the first trajectory takes into account the last received values different from the current values of the operating or environmental parameters of the UAV representing the detected severe hazard, the second trajectory is selected.

[0064] Therefore, on the UAV, when switching to the emergency landing mode, there may be a choice between two solutions: one solution from the ground and one solution calculated on board. The selection function determines which of these two solutions is the most relevant.

[0065] A data set defining the reasons for the emergency switch is associated with each emergency trajectory: low battery, position loss, device loss, etc. These data may have an impact on the calculated emergency solutions.

[0066] For example, the constraints related to the remaining autonomy can reduce the landing point search area.

[0067] The selection mechanism of module 10 operates as follows:

[0068] - If the data sets associated with the first emergency trajectory and the second emergency trajectory are consistent, then:

[0069] - This means that the ground control station 2 well knows the current constraints detected on the UAV 1;

[0070] - Give priority to the first trajectory determined by the ground control station 2 using a more complex algorithm.

[0071] - Otherwise:

[0072] - Due to transmission problems, the information in the ground control station 2 does not match the information on the UAV 1;

[0073] - The severe hazard detected on the UAV 1 is considered more relevant; and

[0074] - Select the trajectory calculated on board.

[0075] Before the mission, an emergency landing database is created on the ground and loaded on the aircraft at the start of the mission. Figure 2 shows an example of a map representing the emergency landing database.

[0076] These landing zones LZ correspond to zones identified as safe and are modeled by polygons. These polygons are generated using multiple data sources.

[0077] On the landing zones, a safety margin is subtracted (which corresponds to the distance required for the UAV to descend without touching the obstacles that will be at the edge of the landing zone) and uncertainties are taken into account (inaccuracy of the terrain elevation, inaccuracy of the altitude measurement, etc.). This safety margin depends on the type of UAV (technical characteristics) and its capabilities (descent gradient). Thus, any point in the landing zone is a valid landing point.

[0078] The emergency landing database also includes no-fly zones.

[0079] Alternatively, the landing database may include landing points with associated final approach axes and associated altitudes.

[0080] The determination module 8 is used to continuously determine a second emergency landing trajectory based on the emergency landing database and the current value of at least one operating or environmental parameter of the UAV 1.

[0081] The determination module 8 continuously determining the second emergency landing trajectory on the UAV 1 includes the following main steps:

[0082] - Determine eligible landing points, if necessary, i.e., if the landing database does not already contain them;

[0083] - For each landing point:

[0084] - Calculate the lateral trajectory;

[0085] - Calculate the vertical trajectory; and

[0086] - Check that the trajectory is safe (define a safety corridor and check that it does not coincide with no-fly zones or obstacles).

[0087] If the landing database does not directly contain landing points but contains landing zones, the eligible landing points are determined by module 8 as follows, as Figure 3 shown.

[0088] Determine the search area in which to look for landing points.

[0089] This area is delimited by an arc of a circle or a circle and the current heading of the drone. The circle is centered on the position of the drone and extrapolated back X seconds (X being the calculation frequency of this emergency solution of the second computer 7). The length of this area corresponds to the maximum distance traveled by the drone in an emergency: for example, two or three minutes in this case.

[0090] The angle of the search area can be set according to the performance of the drone or various external constraints.

[0091] Then, the polygons in the landing database previously loaded on the drone 1 are evaluated with respect to this search area. Only the polygon segments included in the search area are considered. If necessary, they are limited to the boundaries of the search area.

[0092] A polar coordinate projection is performed to make it easy to determine which areas are directly visible on a straight line from the center of the search area, in which angular sectors, and at what distances.

[0093] Then, the visible landing areas are identified. The projection identifies the angular sectors and the distances involved to reach the landing zone LZ. The fact that the edges of the landing zone (polygon) take into account a safety margin ensures that any point in the landing zone is a qualified landing point.

[0094] This will determine a set of qualified landing points to be evaluated, for example, by aiming at the centers of the segments of the visible landing zone LZ.

[0095] It may be necessary to determine a specific landing axis according to the type of the drone 1 or flight conditions such as wind to improve landing safety.

[0096] In this case, from the qualified landing points, projections can be repeated within the landing zone in order to determine the landing axis (or several landing axes) leaving enough distance to land within the zone.

[0097] Other parameters such as wind direction can be considered.

[0098] Then, each landing point and its associated final approach axis and its associated altitude must be evaluated for two cases of landing, the landing zone or the landing point database.

[0099] Multiple evaluation strategies are possible, for example, from the nearest to the farthest, or from the nearest to the farthest from the minimum landing distance.

[0100] Each landing point evaluation performs the following steps.

[0101] First, the lateral trajectory is calculated, as Figure 4 shown. The lateral trajectory calculation looks for the most direct joining trajectory from a given position and heading in order to reach a given point at a given heading.

[0102] The starting point of the algorithm is the center of the search area and the current heading of the drone. The end point corresponds to the start of the approach. It is positioned along the landing axis before the landing point. Then a (straight-line) approach section is added at the end of the trajectory.

[0103] Then the vertical trajectory is calculated, as shown in 3D in Figure 5 , which takes into account the terrain altitude available in the terrain database on the drone 1 and the characteristics of the drone 1.

[0104] The trajectory must also comply with terrain-following constraints to ensure that it remains flyable without the risk of colliding with the terrain. If this is not possible, the landing point is rejected or ignored.

[0105] Finally, the trajectory is checked to ensure that it does not coincide with a prohibited area or an obstacle (integrated as a prohibited area into the database). For this purpose, a safety corridor around the trajectory is considered. If this is not possible, the landing point is ignored.

[0106] Once a qualified landing point has allowed the calculation of a safe trajectory, the calculation can stop: an effective solution has been found.

[0107] All these calculations are continuously performed on the drone 1 at a certain calculation frequency, which is limited by the capabilities of the second computer 7. Therefore, the landing solution is updated periodically from the measured context.

[0108] If the selection module 10 selects an emergency trajectory for flight, a new emergency trajectory is continuously recalculated in order to propose an appropriate solution for a change in the critical danger on the drone 1.

[0109] The determination module 4 for continuously determining the first emergency landing trajectory first constructs a path considering the no-fly zone NFZ. The computing power of the first computer 3 of the ground station 2 is generally greater than the computing power of the drone 1 in the second computer 7, and allows the use of pathfinding algorithms (Theta* or Field D*) or the RRT (rapidly-exploring random tree) algorithm on the ground.

[0110] Then this path is provided to the trajectory calculation algorithm in order to calculate the first 3D landing trajectory considering the terrain. Then the first trajectory is provided to the first trajectory verification module 5. Its role is to ensure that the trajectory is flyable by proposing a design assurance level (DAL) equal to the algorithm installed on the drone 1. This algorithm is used to verify that the trajectory is flyable in terms of continuity and performance, without conflicts with the terrain, obstacles, and no-fly zones. The result of the check and the trajectory are sent to the drone 1.

[0111] The resulting trajectory is sent to the drone periodically or intermittently in order to be considered in the case of a critical danger where a switch to the emergency mode is required.

[0112] Thus, the present invention ensures that the emergency landing trajectory is always available throughout the mission, responding to the nature of the serious danger encountered.

[0113] The dynamic calculation of the trajectory considering the current situation of the drone 1 avoids preloading a large number of solutions on board. This reduces the storage capacity that needs to be allocated to trajectory storage.

[0114] The solution continues to operate even if the communication between the ground station 2 and the drone 1 is lost.

[0115] The use of a simple algorithm on the drone 1 enables the high-speed simulation of the flight route to prepare the mission in order to identify sections not covered by the emergency solution.

Claims

1. A system for managing an emergency landing trajectory of an unmanned aerial vehicle (1), comprising: - A ground control station (2), the ground control station (2) including a first computer (3) equipped with: - A determination module (4) for continuously determining a first emergency landing trajectory considering the last value of at least one parameter representing the operation or environment of the unmanned aerial vehicle and an emergency landing database, the value being received from the unmanned aerial vehicle, the determination module (4) being configured to calculate the first emergency landing trajectory according to a path search algorithm, the emergency landing database, and the last received value of the operation or environment parameters of the unmanned aerial vehicle; And - A verification module (5) for verifying the first trajectory according to the emergency landing database; And - A control unit (6) on the unmanned aerial vehicle (1), the control unit (6) including a second computer (7), the second computer (7) including: - A determination module (8) for continuously determining a second emergency landing trajectory according to the emergency landing database and the current value of at least one operation or environment parameter of the unmanned aerial vehicle, the determination module (8) being configured to calculate the second emergency landing trajectory by including lateral trajectory calculation and vertical trajectory calculation for each emergency landing point, and the determination module (8) being configured to check that the emergency trajectory is fixed in a safety corridor according to the emergency landing database and the last value of the operation or environment parameters of the unmanned aerial vehicle; - A detection module (9) for detecting a severe hazard, the severe hazard relating to a switch of the emergency landing mode, a hazard that has been detected according to the current value of at least one operation or environment parameter of the unmanned aerial vehicle, the emergency landing mode activating the function of a selection module for selecting the first emergency landing trajectory or the second emergency landing trajectory; and - A selection module (10) configured to select the first designed emergency landing trajectory or the second emergency landing trajectory in the following manner: if the first trajectory considers the current value of the operation or environment parameter of the unmanned aerial vehicle representing the detected severe hazard, select the first trajectory, and if the first trajectory considers a last received value different from the current value of the operation or environment parameter of the unmanned aerial vehicle representing the detected severe hazard, select the second trajectory.

2. The system according to claim 1, wherein The landing database includes a polygonal landing zone (LZ), a no-fly zone (NFZ), and obstacles.

3. The system according to claim 1, wherein The landing database includes landing points, no-fly zones, and obstacles with associated final approach axes and associated heights.

4. The system according to claim 2, wherein, The determination module (8) for continuously determining the second emergency landing trajectory is configured to calculate an emergency landing point by: defining a landing point search area; identifying a section of a polygon that is directly visible in a straight line; and for each landing point, performing the following operations: - Determining the final approach axis of each landing point; and - Check compliance with the safety corridor of the trajectory to avoid no - fly zones and obstacles.

5. The system according to claim 3 or 4, wherein, The determination module (8) for continuously determining a second emergency landing trajectory is configured to evaluate the landing points in order from the closest to the farthest by calculating a lateral trajectory, an emergency landing vertical trajectory, and an associated safety corridor.

6. The system according to one of the preceding claims, wherein, The second computer (7) has less computing power compared to the first computer (3).

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